scientific research paper sections

Educational resources and simple solutions for your research journey

How to Write the Methods Section of a Research Paper

Writing a research paper is both an art and a skill, and knowing how to write the methods section of a research paper is the first crucial step in mastering scientific writing. If, like the majority of early career researchers, you believe that the methods section is the simplest to write and needs little in the way of careful consideration or thought, this article will help you understand it is not 1 .

We have all probably asked our supervisors, coworkers, or search engines “ how to write a methods section of a research paper ” at some point in our scientific careers, so you are not alone if that’s how you ended up here.  Even for seasoned researchers, selecting what to include in the methods section from a wealth of experimental information can occasionally be a source of distress and perplexity.   

Additionally, journal specifications, in some cases, may make it more of a requirement rather than a choice to provide a selective yet descriptive account of the experimental procedure. Hence, knowing these nuances of how to write the methods section of a research paper is critical to its success. The methods section of the research paper is not supposed to be a detailed heavy, dull section that some researchers tend to write; rather, it should be the central component of the study that justifies the validity and reliability of the research.

Are you still unsure of how the methods section of a research paper forms the basis of every investigation? Consider the last article you read but ignore the methods section and concentrate on the other parts of the paper . Now think whether you could repeat the study and be sure of the credibility of the findings despite knowing the literature review and even having the data in front of you. You have the answer!   

Having established the importance of the methods section , the next question is how to write the methods section of a research paper that unifies the overall study. The purpose of the methods section , which was earlier called as Materials and Methods , is to describe how the authors went about answering the “research question” at hand. Here, the objective is to tell a coherent story that gives a detailed account of how the study was conducted, the rationale behind specific experimental procedures, the experimental setup, objects (variables) involved, the research protocol employed, tools utilized to measure, calculations and measurements, and the analysis of the collected data 2 .

In this article, we will take a deep dive into this topic and provide a detailed overview of how to write the methods section of a research paper . For the sake of clarity, we have separated the subject into various sections with corresponding subheadings.  

Table of Contents

What is the methods section of a research paper ?  

The methods section is a fundamental section of any paper since it typically discusses the ‘ what ’, ‘ how ’, ‘ which ’, and ‘ why ’ of the study, which is necessary to arrive at the final conclusions. In a research article, the introduction, which serves to set the foundation for comprehending the background and results is usually followed by the methods section, which precedes the result and discussion sections. The methods section must explicitly state what was done, how it was done, which equipment, tools and techniques were utilized, how were the measurements/calculations taken, and why specific research protocols, software, and analytical methods were employed.  

Why is the methods section important?  

The primary goal of the methods section is to provide pertinent details about the experimental approach so that the reader may put the results in perspective and, if necessary, replicate the findings 3 .  This section offers readers the chance to evaluate the reliability and validity of any study. In short, it also serves as the study’s blueprint, assisting researchers who might be unsure about any other portion in establishing the study’s context and validity. The methods plays a rather crucial role in determining the fate of the article; an incomplete and unreliable methods section can frequently result in early rejections and may lead to numerous rounds of modifications during the publication process. This means that the reviewers also often use methods section to assess the reliability and validity of the research protocol and the data analysis employed to address the research topic. In other words, the purpose of the methods section is to demonstrate the research acumen and subject-matter expertise of the author(s) in their field.  

Structure of methods section of a research paper  

Similar to the research paper, the methods section also follows a defined structure; this may be dictated by the guidelines of a specific journal or can be presented in a chronological or thematic manner based on the study type. When writing the methods section , authors should keep in mind that they are telling a story about how the research was conducted. They should only report relevant information to avoid confusing the reader and include details that would aid in connecting various aspects of the entire research activity together. It is generally advisable to present experiments in the order in which they were conducted. This facilitates the logical flow of the research and allows readers to follow the progression of the study design.   

It is also essential to clearly state the rationale behind each experiment and how the findings of earlier experiments informed the design or interpretation of later experiments. This allows the readers to understand the overall purpose of the study design and the significance of each experiment within that context. However, depending on the particular research question and method, it may make sense to present information in a different order; therefore, authors must select the best structure and strategy for their individual studies.   

In cases where there is a lot of information, divide the sections into subheadings to cover the pertinent details. If the journal guidelines pose restrictions on the word limit , additional important information can be supplied in the supplementary files. A simple rule of thumb for sectioning the method section is to begin by explaining the methodological approach ( what was done ), describing the data collection methods ( how it was done ), providing the analysis method ( how the data was analyzed ), and explaining the rationale for choosing the methodological strategy. This is described in detail in the upcoming sections.    

How to write the methods section of a research paper  

Contrary to widespread assumption, the methods section of a research paper should be prepared once the study is complete to prevent missing any key parameter. Hence, please make sure that all relevant experiments are done before you start writing a methods section . The next step for authors is to look up any applicable academic style manuals or journal-specific standards to ensure that the methods section is formatted correctly. The methods section of a research paper typically constitutes materials and methods; while writing this section, authors usually arrange the information under each category.

The materials category describes the samples, materials, treatments, and instruments, while experimental design, sample preparation, data collection, and data analysis are a part of the method category. According to the nature of the study, authors should include additional subsections within the methods section, such as ethical considerations like the declaration of Helsinki (for studies involving human subjects), demographic information of the participants, and any other crucial information that can affect the output of the study. Simply put, the methods section has two major components: content and format. Here is an easy checklist for you to consider if you are struggling with how to write the methods section of a research paper .   

• Explain the research design, subjects, and sample details  
• Include information on inclusion and exclusion criteria  
• Mention ethical or any other permission required for the study  
• Include information about materials, experimental setup, tools, and software  
• Add details of data collection and analysis methods  
• Incorporate how research biases were avoided or confounding variables were controlled  
• Evaluate and justify the experimental procedure selected to address the research question  
• Provide precise and clear details of each experiment  
• Flowcharts, infographics, or tables can be used to present complex information     
• Use past tense to show that the experiments have been done   
• Follow academic style guides (such as APA or MLA ) to structure the content  
• Citations should be included as per standard protocols in the field  

Now that you know how to write the methods section of a research paper , let’s address another challenge researchers face while writing the methods section —what to include in the methods section .  How much information is too much is not always obvious when it comes to trying to include data in the methods section of a paper. In the next section, we examine this issue and explore potential solutions.   

What to include in the methods section of a research paper  

The technical nature of the methods section occasionally makes it harder to present the information clearly and concisely while staying within the study context. Many young researchers tend to veer off subject significantly, and they frequently commit the sin of becoming bogged down in itty bitty details, making the text harder to read and impairing its overall flow. However, the best way to write the methods section is to start with crucial components of the experiments. If you have trouble deciding which elements are essential, think about leaving out those that would make it more challenging to comprehend the context or replicate the results. The top-down approach helps to ensure all relevant information is incorporated and vital information is not lost in technicalities. Next, remember to add details that are significant to assess the validity and reliability of the study. Here is a simple checklist for you to follow ( bonus tip: you can also make a checklist for your own study to avoid missing any critical information while writing the methods section ).  

• Structuring the methods section : Authors should diligently follow journal guidelines and adhere to the specific author instructions provided when writing the methods section . Journals typically have specific guidelines for formatting the methods section ; for example, Frontiers in Plant Sciences advises arranging the materials and methods section by subheading and citing relevant literature. There are several standardized checklists available for different study types in the biomedical field, including CONSORT (Consolidated Standards of Reporting Trials) for randomized clinical trials, PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analysis) for systematic reviews and meta-analysis, and STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) for cohort, case-control, cross-sectional studies. Before starting the methods section , check the checklist available in your field that can function as a guide.     
• Organizing different sections to tell a story : Once you are sure of the format required for structuring the methods section , the next is to present the sections in a logical manner; as mentioned earlier, the sections can be organized according to the chronology or themes. In the chronological arrangement, you should discuss the methods in accordance with how the experiments were carried out. An example of the method section of a research paper of an animal study should first ideally include information about the species, weight, sex, strain, and age. Next, the number of animals, their initial conditions, and their living and housing conditions should also be mentioned. Second, how the groups are assigned and the intervention (drug treatment, stress, or other) given to each group, and finally, the details of tools and techniques used to measure, collect, and analyze the data. Experiments involving animal or human subjects should additionally state an ethics approval statement. It is best to arrange the section using the thematic approach when discussing distinct experiments not following a sequential order.  
• Define and explain the objects and procedure: Experimental procedure should clearly be stated in the methods section . Samples, necessary preparations (samples, treatment, and drug), and methods for manipulation need to be included. All variables (control, dependent, independent, and confounding) must be clearly defined, particularly if the confounding variables can affect the outcome of the study.  
• Match the order of the methods section with the order of results: Though not mandatory, organizing the manuscript in a logical and coherent manner can improve the readability and clarity of the paper. This can be done by following a consistent structure throughout the manuscript; readers can easily navigate through the different sections and understand the methods and results in relation to each other. Using experiment names as headings for both the methods and results sections can also make it simpler for readers to locate specific information and corroborate it if needed.   
• Relevant information must always be included: The methods section should have information on all experiments conducted and their details clearly mentioned. Ask the journal whether there is a way to offer more information in the supplemental files or external repositories if your target journal has strict word limitations. For example, Nature communications encourages authors to deposit their step-by-step protocols in an open-resource depository, Protocol Exchange which allows the protocols to be linked with the manuscript upon publication. Providing access to detailed protocols also helps to increase the transparency and reproducibility of the research.  
• It’s all in the details: The methods section should meticulously list all the materials, tools, instruments, and software used for different experiments. Specify the testing equipment on which data was obtained, together with its manufacturer’s information, location, city, and state or any other stimuli used to manipulate the variables. Provide specifics on the research process you employed; if it was a standard protocol, cite previous studies that also used the protocol.  Include any protocol modifications that were made, as well as any other factors that were taken into account when planning the study or gathering data. Any new or modified techniques should be explained by the authors. Typically, readers evaluate the reliability and validity of the procedures using the cited literature, and a widely accepted checklist helps to support the credibility of the methodology. Note: Authors should include a statement on sample size estimation (if applicable), which is often missed. It enables the reader to determine how many subjects will be required to detect the expected change in the outcome variables within a given confidence interval.  
• Write for the audience: While explaining the details in the methods section , authors should be mindful of their target audience, as some of the rationale or assumptions on which specific procedures are based might not always be obvious to the audience, particularly for a general audience. Therefore, when in doubt, the objective of a procedure should be specified either in relation to the research question or to the entire protocol.  
• Data interpretation and analysis : Information on data processing, statistical testing, levels of significance, and analysis tools and software should be added. Mention if the recommendations and expertise of an experienced statistician were followed. Also, evaluate and justify the preferred statistical method used in the study and its significance.  

What NOT to include in the methods section of a research paper  

To address “ how to write the methods section of a research paper ”, authors should not only pay careful attention to what to include but also what not to include in the methods section of a research paper . Here is a list of do not’s when writing the methods section :  

• Do not elaborate on specifics of standard methods/procedures: You should refrain from adding unnecessary details of experiments and practices that are well established and cited previously.  Instead, simply cite relevant literature or mention if the manufacturer’s protocol was followed.  
• Do not add unnecessary details : Do not include minute details of the experimental procedure and materials/instruments used that are not significant for the outcome of the experiment. For example, there is no need to mention the brand name of the water bath used for incubation.    
• Do not discuss the results: The methods section is not to discuss the results or refer to the tables and figures; save it for the results and discussion section. Also, focus on the methods selected to conduct the study and avoid diverting to other methods or commenting on their pros or cons.  
• Do not make the section bulky : For extensive methods and protocols, provide the essential details and share the rest of the information in the supplemental files. The writing should be clear yet concise to maintain the flow of the section.  

We hope that by this point, you understand how crucial it is to write a thoughtful and precise methods section and the ins and outs of how to write the methods section of a research paper . To restate, the entire purpose of the methods section is to enable others to reproduce the results or verify the research. We sincerely hope that this post has cleared up any confusion and given you a fresh perspective on the methods section .

As a parting gift, we’re leaving you with a handy checklist that will help you understand how to write the methods section of a research paper . Feel free to download this checklist and use or share this with those who you think may benefit from it.  

References  

• Bhattacharya, D. How to write the Methods section of a research paper. Editage Insights, 2018. https://www.editage.com/insights/how-to-write-the-methods-section-of-a-research-paper (2018).
• Kallet, R. H. How to Write the Methods Section of a Research Paper. Respiratory Care 49, 1229–1232 (2004). https://pubmed.ncbi.nlm.nih.gov/15447808/
• Grindstaff, T. L. & Saliba, S. A. AVOIDING MANUSCRIPT MISTAKES. Int J Sports Phys Ther 7, 518–524 (2012). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3474299/

Editage All Access is a subscription-based platform that unifies the best AI tools and services designed to speed up, simplify, and streamline every step of a researcher’s journey. The Editage All Access Pack is a one-of-a-kind subscription that unlocks full access to an AI writing assistant, literature recommender, journal finder, scientific illustration tool, and exclusive discounts on professional publication services from Editage.  

Based on 22+ years of experience in academia, Editage All Access empowers researchers to put their best research forward and move closer to success. Explore our top AI Tools pack, AI Tools + Publication Services pack, or Build Your Own Plan. Find everything a researcher needs to succeed, all in one place –  Get All Access now starting at just $14 a month !    

Related Posts

What is IMRaD Format in Research?

What is a Review Article? How to Write it?

Penn State University Libraries

Computer science and engineering.

• Reference Sources
• Finding Articles and Databases
• Finding Books
• Finding Websites
• Penn State Resources and Organizations
• Books, Articles, and Other Educational Resources
• Research Tips
• Main Parts of a Scientific/Technical Paper
• Technical Writing Resources
• Ten Tips for Technical Writing
• Professional Organizations

Parts of a Technical Paper

The basic parts of a scientific or technical paper are:

Title and Author Information Abstract Introduction Literature Review Methods Results Discussion Conclusions References and Appendices

Detailed Explanation for Each Part

Title and Author Information:

The title of your paper and any needed information about yourself (usually your name and institution).

A short (usually around 250-400 words) description of the paper. Should include what the purpose of the paper is (including the basic research question/problem), the basic design of your project, and the major findings.

Introduction:

A general introduction to your topic and what you expect to learn from your project or experiment. Your research question should be found here.

Literature Review:

An analysis of what has already been published about your chosen topic. Should be able to show how your research question fits into the context of your field.

A description of everything you did in your experiment or project, step-by-step. Needs to be detailed enough so that any reader would be able to repeat each step exactly on their own.

What actually happened during your project or what you found at the end of your experiment. This is usually the best part to include the majority of your graphs, photos, tables, and other visual aids, as long as they help explain the results of your work.

Discussion:

An analysis of the results that integrates what you found into the wider body of research in your field. Can also include future hypotheses to be tested or future projects to build from your own.

Conclusion:

Can be included in the discussion if necessary. A final summary of the paper, including whether or not you were able to answer your original research question.

References and Appendices:

The reference page(s) is a list of all the sources you used to research and create your project/experiment, including everything cited in the literature review and methods sections. Remember to use the same citation style throughout the paper. An appendix would include any additional information about your work that you were not able to include within the body of your paper (like large datasets and figures) that would help readers better understand your results.

• << Previous: Technical Writing
• Next: Technical Writing Resources >>
• Last Updated: Jul 11, 2024 8:43 AM
• URL: https://guides.libraries.psu.edu/compsciandengin

• Locations and Hours
• UCLA Library
• Research Guides

Scientific Writing

• Sections of a Paper
• Literature Reviews

Example Paper

• Scientific Writing Infographic
• Citing Sources
• Writer's Block
• Getting Published

Introduction

• Materials & Methods

Typically scientific journal articles have the following sections:

Materials & Methods

References used:

Kotsis, S.V. and Chung, K.C. (2010) A Guide for Writing in the Scientific Forum. Plastic and Reconstructive Surgery. 126(5):1763-71. PubMed ID:  21042135

Van Way, C.W. (2007) Writing a Scientific Paper. Nutrition in Clinical Practice. 22: 663-40. PubMed ID:  1804295

What to include:

• Background/Objectives: include the hypothesis
• Methods: Briefly explain the type of study, sample/population size and description, the design, and any particular techniques for data collection and analysis
• Results: Essential data, including statistically significant data (use # & %)
• Conclusions: Summarize interpretations of results and explain if hypothesis was supported or rejected
• Be concise!
• Emphasize the methods and results
• Do not copy the introduction
• Only include data that is included in the paper
• Write the abstract last
• Avoid jargon and ambiguity
• Should stand-alone

Additional resources: Fisher, W.E. (2005) Abstract Writing. Journal of Surgical Research. 128(2):162-4. PubMed ID:  16165161

Peh, W.C. and Ng, K.H. (2008) Abstract and keywords. Singapore Medical Journal. 49(9): 664-6. PubMed ID:  18830537

• How does your study fit into what has been done
• Explain evidence using limited # of references
• Why is it important
• How does it relate to previous research
• State hypothesis at the end
• Use present tense
• Be succinct
• Clearly state objectives
• Explain important work done

Additional resources: Annesley, T. M. (2010) "It was a cold and rainy night": set the scene with a good introduction. Clinical Chemistry. 56(5):708-13. PubMed ID:  20207764 Peh, W.C. and Ng, K.H. (2008) Writing the introduction. Singapore Medical Journal. 49(10):756-8. PubMed ID:  18946606  

• What was done
• Include characteristics
• Describe recruitment, participation, withdrawal, etc.
• Type of study (RCT, cohort, case-controlled, etc.)
• Equipment used
• Measurements made
• Usually the final paragraph
• Include enough details so others can duplicate study
• Use past tense
• Be direct and precise
• Include any preliminary results
• Ask for help from a statistician to write description of statistical analysis
• Be systematic

Additional resources: Lallet, R. H. (2004) How to write the methods section of a research paper. Respiratory Care. 49(10): 1229-32. PubMed ID:  15447808 Ng, K.H. and Peh, W.C. (2008) Writing the materials and methods. Singapore Medical Journal. 49(11): 856-9. PubMed ID:  19037549

• Describe study sample demographics
• Include statistical significance and the statistical test used
• Use tables and figures when appropriate
• Present in a logical sequence
• Facts only - no citations or interpretations
• Should stand alone (not need written descriptions to be understood)
• Include title, legend, and axes labels
• Include raw numbers with percentages
• General phrases (significance, show trend, etc. should be used with caution)
• Data is plural ("Our data are" is correct, "Our data is" is in-correct)

Additional resources: Ng, K.H and Peh, W.C. (2008) Writing the results. Singapore Medical Journal. 49(12):967-9. PubMed ID:  19122944 Streiner, D.L. (2007) A shortcut to rejection: how not to write the results section of a paper. Canadian Journal of Psychiatry. 52(6):385-9. PubMed ID:  17696025

• Did you reject your null hypothesis?
• Include a focused review of literature in relation to results
• Explain meaning of statistical findings
• Explain importance/relevance 
• Include all possible explanations
• Discuss possible limitations of study
• Suggest future work that could be done
• Use past tense to describe your study and present tense to describe established knowledge from literature
• Don't criticize other studies, contrast it with your work
• Don't make conclusions not supported by your results
• Stay focused and concise
• Include key, relevant references
• It is considered good manners to include an acknowledgements section

Additional resources: Annesley, T. M. (2010) The discussion section: your closing argument. Clinical Chemistry. 56(11):1671-4. PubMed ID:  20833779 Ng, K.H. and Peh, W.C. (2009) Writing the discussion. Singapore Medical Journal. 50(5):458-61. PubMed ID:  19495512

Tables & Figures: Durbin, C. G. (2004) Effective use of tables and figures in abstracts, presentations, and papers. Respiratory Care. 49(10): 1233-7. PubMed ID:  15447809 Ng, K. H. and Peh, W.C.G. (2009) Preparing effective tables. Singapore Medical Journal. (50)2: 117-9. PubMed ID:  19296024

Statistics: Ng, K. H. and Peh, W.C.G. (2009) Presenting the statistical results. Singapore Medical Journal. (50)1: 11-4. PubMed ID:  19224078

References: Peh, W.C.G. and Ng, K. H. (2009) Preparing the references. Singapore Medical Journal. (50)7: 11-4. PubMed ID:  19644619

The link below includes more detailed descriptions for each section along with examples of a scientific paper.

Guide from Scitable by Nature Education

• << Previous: Literature Reviews
• Next: Books & Journals >>
• Last Updated: Jul 23, 2024 3:38 PM
• URL: https://guides.library.ucla.edu/scientificwriting

• USC Libraries
• Research Guides

Organizing Your Social Sciences Research Paper

• 8. The Discussion
• Purpose of Guide
• Design Flaws to Avoid
• Independent and Dependent Variables
• Glossary of Research Terms
• Reading Research Effectively
• Narrowing a Topic Idea
• Broadening a Topic Idea
• Extending the Timeliness of a Topic Idea
• Academic Writing Style
• Applying Critical Thinking
• Choosing a Title
• Making an Outline
• Paragraph Development
• Research Process Video Series
• Executive Summary
• The C.A.R.S. Model
• Background Information
• The Research Problem/Question
• Theoretical Framework
• Citation Tracking
• Content Alert Services
• Evaluating Sources
• Primary Sources
• Secondary Sources
• Tiertiary Sources
• Scholarly vs. Popular Publications
• Qualitative Methods
• Quantitative Methods
• Insiderness
• Using Non-Textual Elements
• Limitations of the Study
• Common Grammar Mistakes
• Writing Concisely
• Avoiding Plagiarism
• Footnotes or Endnotes?
• Further Readings
• Generative AI and Writing
• USC Libraries Tutorials and Other Guides
• Bibliography

The purpose of the discussion section is to interpret and describe the significance of your findings in relation to what was already known about the research problem being investigated and to explain any new understanding or insights that emerged as a result of your research. The discussion will always connect to the introduction by way of the research questions or hypotheses you posed and the literature you reviewed, but the discussion does not simply repeat or rearrange the first parts of your paper; the discussion clearly explains how your study advanced the reader's understanding of the research problem from where you left them at the end of your review of prior research.

Annesley, Thomas M. “The Discussion Section: Your Closing Argument.” Clinical Chemistry 56 (November 2010): 1671-1674; Peacock, Matthew. “Communicative Moves in the Discussion Section of Research Articles.” System 30 (December 2002): 479-497.

Importance of a Good Discussion

The discussion section is often considered the most important part of your research paper because it:

• Most effectively demonstrates your ability as a researcher to think critically about an issue, to develop creative solutions to problems based upon a logical synthesis of the findings, and to formulate a deeper, more profound understanding of the research problem under investigation;
• Presents the underlying meaning of your research, notes possible implications in other areas of study, and explores possible improvements that can be made in order to further develop the concerns of your research;
• Highlights the importance of your study and how it can contribute to understanding the research problem within the field of study;
• Presents how the findings from your study revealed and helped fill gaps in the literature that had not been previously exposed or adequately described; and,
• Engages the reader in thinking critically about issues based on an evidence-based interpretation of findings; it is not governed strictly by objective reporting of information.

Annesley Thomas M. “The Discussion Section: Your Closing Argument.” Clinical Chemistry 56 (November 2010): 1671-1674; Bitchener, John and Helen Basturkmen. “Perceptions of the Difficulties of Postgraduate L2 Thesis Students Writing the Discussion Section.” Journal of English for Academic Purposes 5 (January 2006): 4-18; Kretchmer, Paul. Fourteen Steps to Writing an Effective Discussion Section. San Francisco Edit, 2003-2008.

Structure and Writing Style

I.  General Rules

These are the general rules you should adopt when composing your discussion of the results :

• Do not be verbose or repetitive; be concise and make your points clearly
• Avoid the use of jargon or undefined technical language
• Follow a logical stream of thought; in general, interpret and discuss the significance of your findings in the same sequence you described them in your results section [a notable exception is to begin by highlighting an unexpected result or a finding that can grab the reader's attention]
• Use the present verb tense, especially for established facts; however, refer to specific works or prior studies in the past tense
• If needed, use subheadings to help organize your discussion or to categorize your interpretations into themes

II.  The Content

The content of the discussion section of your paper most often includes :

• Explanation of results : Comment on whether or not the results were expected for each set of findings; go into greater depth to explain findings that were unexpected or especially profound. If appropriate, note any unusual or unanticipated patterns or trends that emerged from your results and explain their meaning in relation to the research problem.
• References to previous research : Either compare your results with the findings from other studies or use the studies to support a claim. This can include re-visiting key sources already cited in your literature review section, or, save them to cite later in the discussion section if they are more important to compare with your results instead of being a part of the general literature review of prior research used to provide context and background information. Note that you can make this decision to highlight specific studies after you have begun writing the discussion section.
• Deduction : A claim for how the results can be applied more generally. For example, describing lessons learned, proposing recommendations that can help improve a situation, or highlighting best practices.
• Hypothesis : A more general claim or possible conclusion arising from the results [which may be proved or disproved in subsequent research]. This can be framed as new research questions that emerged as a consequence of your analysis.

III.  Organization and Structure

Keep the following sequential points in mind as you organize and write the discussion section of your paper:

• Think of your discussion as an inverted pyramid. Organize the discussion from the general to the specific, linking your findings to the literature, then to theory, then to practice [if appropriate].
• Use the same key terms, narrative style, and verb tense [present] that you used when describing the research problem in your introduction.
• Begin by briefly re-stating the research problem you were investigating and answer all of the research questions underpinning the problem that you posed in the introduction.
• Describe the patterns, principles, and relationships shown by each major findings and place them in proper perspective. The sequence of this information is important; first state the answer, then the relevant results, then cite the work of others. If appropriate, refer the reader to a figure or table to help enhance the interpretation of the data [either within the text or as an appendix].
• Regardless of where it's mentioned, a good discussion section includes analysis of any unexpected findings. This part of the discussion should begin with a description of the unanticipated finding, followed by a brief interpretation as to why you believe it appeared and, if necessary, its possible significance in relation to the overall study. If more than one unexpected finding emerged during the study, describe each of them in the order they appeared as you gathered or analyzed the data. As noted, the exception to discussing findings in the same order you described them in the results section would be to begin by highlighting the implications of a particularly unexpected or significant finding that emerged from the study, followed by a discussion of the remaining findings.
• Before concluding the discussion, identify potential limitations and weaknesses if you do not plan to do so in the conclusion of the paper. Comment on their relative importance in relation to your overall interpretation of the results and, if necessary, note how they may affect the validity of your findings. Avoid using an apologetic tone; however, be honest and self-critical [e.g., in retrospect, had you included a particular question in a survey instrument, additional data could have been revealed].
• The discussion section should end with a concise summary of the principal implications of the findings regardless of their significance. Give a brief explanation about why you believe the findings and conclusions of your study are important and how they support broader knowledge or understanding of the research problem. This can be followed by any recommendations for further research. However, do not offer recommendations which could have been easily addressed within the study. This would demonstrate to the reader that you have inadequately examined and interpreted the data.

IV.  Overall Objectives

The objectives of your discussion section should include the following: I.  Reiterate the Research Problem/State the Major Findings

Briefly reiterate the research problem or problems you are investigating and the methods you used to investigate them, then move quickly to describe the major findings of the study. You should write a direct, declarative, and succinct proclamation of the study results, usually in one paragraph.

II.  Explain the Meaning of the Findings and Why They are Important

No one has thought as long and hard about your study as you have. Systematically explain the underlying meaning of your findings and state why you believe they are significant. After reading the discussion section, you want the reader to think critically about the results and why they are important. You don’t want to force the reader to go through the paper multiple times to figure out what it all means. If applicable, begin this part of the section by repeating what you consider to be your most significant or unanticipated finding first, then systematically review each finding. Otherwise, follow the general order you reported the findings presented in the results section.

III.  Relate the Findings to Similar Studies

No study in the social sciences is so novel or possesses such a restricted focus that it has absolutely no relation to previously published research. The discussion section should relate your results to those found in other studies, particularly if questions raised from prior studies served as the motivation for your research. This is important because comparing and contrasting the findings of other studies helps to support the overall importance of your results and it highlights how and in what ways your study differs from other research about the topic. Note that any significant or unanticipated finding is often because there was no prior research to indicate the finding could occur. If there is prior research to indicate this, you need to explain why it was significant or unanticipated. IV.  Consider Alternative Explanations of the Findings

It is important to remember that the purpose of research in the social sciences is to discover and not to prove . When writing the discussion section, you should carefully consider all possible explanations for the study results, rather than just those that fit your hypothesis or prior assumptions and biases. This is especially important when describing the discovery of significant or unanticipated findings.

V.  Acknowledge the Study’s Limitations

It is far better for you to identify and acknowledge your study’s limitations than to have them pointed out by your professor! Note any unanswered questions or issues your study could not address and describe the generalizability of your results to other situations. If a limitation is applicable to the method chosen to gather information, then describe in detail the problems you encountered and why. VI.  Make Suggestions for Further Research

You may choose to conclude the discussion section by making suggestions for further research [as opposed to offering suggestions in the conclusion of your paper]. Although your study can offer important insights about the research problem, this is where you can address other questions related to the problem that remain unanswered or highlight hidden issues that were revealed as a result of conducting your research. You should frame your suggestions by linking the need for further research to the limitations of your study [e.g., in future studies, the survey instrument should include more questions that ask..."] or linking to critical issues revealed from the data that were not considered initially in your research.

NOTE: Besides the literature review section, the preponderance of references to sources is usually found in the discussion section . A few historical references may be helpful for perspective, but most of the references should be relatively recent and included to aid in the interpretation of your results, to support the significance of a finding, and/or to place a finding within a particular context. If a study that you cited does not support your findings, don't ignore it--clearly explain why your research findings differ from theirs.

V.  Problems to Avoid

• Do not waste time restating your results . Should you need to remind the reader of a finding to be discussed, use "bridge sentences" that relate the result to the interpretation. An example would be: “In the case of determining available housing to single women with children in rural areas of Texas, the findings suggest that access to good schools is important...," then move on to further explaining this finding and its implications.
• As noted, recommendations for further research can be included in either the discussion or conclusion of your paper, but do not repeat your recommendations in the both sections. Think about the overall narrative flow of your paper to determine where best to locate this information. However, if your findings raise a lot of new questions or issues, consider including suggestions for further research in the discussion section.
• Do not introduce new results in the discussion section. Be wary of mistaking the reiteration of a specific finding for an interpretation because it may confuse the reader. The description of findings [results section] and the interpretation of their significance [discussion section] should be distinct parts of your paper. If you choose to combine the results section and the discussion section into a single narrative, you must be clear in how you report the information discovered and your own interpretation of each finding. This approach is not recommended if you lack experience writing college-level research papers.
• Use of the first person pronoun is generally acceptable. Using first person singular pronouns can help emphasize a point or illustrate a contrasting finding. However, keep in mind that too much use of the first person can actually distract the reader from the main points [i.e., I know you're telling me this--just tell me!].

Analyzing vs. Summarizing. Department of English Writing Guide. George Mason University; Discussion. The Structure, Format, Content, and Style of a Journal-Style Scientific Paper. Department of Biology. Bates College; Hess, Dean R. "How to Write an Effective Discussion." Respiratory Care 49 (October 2004); Kretchmer, Paul. Fourteen Steps to Writing to Writing an Effective Discussion Section. San Francisco Edit, 2003-2008; The Lab Report. University College Writing Centre. University of Toronto; Sauaia, A. et al. "The Anatomy of an Article: The Discussion Section: "How Does the Article I Read Today Change What I Will Recommend to my Patients Tomorrow?” The Journal of Trauma and Acute Care Surgery 74 (June 2013): 1599-1602; Research Limitations & Future Research . Lund Research Ltd., 2012; Summary: Using it Wisely. The Writing Center. University of North Carolina; Schafer, Mickey S. Writing the Discussion. Writing in Psychology course syllabus. University of Florida; Yellin, Linda L. A Sociology Writer's Guide . Boston, MA: Allyn and Bacon, 2009.

Writing Tip

Don’t Over-Interpret the Results!

Interpretation is a subjective exercise. As such, you should always approach the selection and interpretation of your findings introspectively and to think critically about the possibility of judgmental biases unintentionally entering into discussions about the significance of your work. With this in mind, be careful that you do not read more into the findings than can be supported by the evidence you have gathered. Remember that the data are the data: nothing more, nothing less.

MacCoun, Robert J. "Biases in the Interpretation and Use of Research Results." Annual Review of Psychology 49 (February 1998): 259-287; Ward, Paulet al, editors. The Oxford Handbook of Expertise . Oxford, UK: Oxford University Press, 2018.

Another Writing Tip

Don't Write Two Results Sections!

One of the most common mistakes that you can make when discussing the results of your study is to present a superficial interpretation of the findings that more or less re-states the results section of your paper. Obviously, you must refer to your results when discussing them, but focus on the interpretation of those results and their significance in relation to the research problem, not the data itself.

Azar, Beth. "Discussing Your Findings."  American Psychological Association gradPSYCH Magazine (January 2006).

Yet Another Writing Tip

Avoid Unwarranted Speculation!

The discussion section should remain focused on the findings of your study. For example, if the purpose of your research was to measure the impact of foreign aid on increasing access to education among disadvantaged children in Bangladesh, it would not be appropriate to speculate about how your findings might apply to populations in other countries without drawing from existing studies to support your claim or if analysis of other countries was not a part of your original research design. If you feel compelled to speculate, do so in the form of describing possible implications or explaining possible impacts. Be certain that you clearly identify your comments as speculation or as a suggestion for where further research is needed. Sometimes your professor will encourage you to expand your discussion of the results in this way, while others don’t care what your opinion is beyond your effort to interpret the data in relation to the research problem.

• << Previous: Using Non-Textual Elements
• Next: Limitations of the Study >>
• Last Updated: Aug 13, 2024 12:57 PM
• URL: https://libguides.usc.edu/writingguide

• Affiliate Program

• UNITED STATES
• 台灣 (TAIWAN)
• TÜRKIYE (TURKEY)
• Academic Editing Services
• - Research Paper
• - Journal Manuscript
• - Dissertation
• - College & University Assignments
• Admissions Editing Services
• - Application Essay
• - Personal Statement
• - Recommendation Letter
• - Cover Letter
• - CV/Resume
• Business Editing Services
• - Business Documents
• - Report & Brochure
• - Website & Blog
• Writer Editing Services
• - Script & Screenplay
• Our Editors
• Client Reviews
• Editing & Proofreading Prices
• Wordvice Points
• Partner Discount
• Plagiarism Checker
• APA Citation Generator
• MLA Citation Generator
• Chicago Citation Generator
• Vancouver Citation Generator
• - APA Style
• - MLA Style
• - Chicago Style
• - Vancouver Style
• Writing & Editing Guide
• Academic Resources
• Admissions Resources

How to Write the Results/Findings Section in Research

What is the research paper Results section and what does it do?

The Results section of a scientific research paper represents the core findings of a study derived from the methods applied to gather and analyze information. It presents these findings in a logical sequence without bias or interpretation from the author, setting up the reader for later interpretation and evaluation in the Discussion section. A major purpose of the Results section is to break down the data into sentences that show its significance to the research question(s).

The Results section appears third in the section sequence in most scientific papers. It follows the presentation of the Methods and Materials and is presented before the Discussion section —although the Results and Discussion are presented together in many journals. This section answers the basic question “What did you find in your research?”

What is included in the Results section?

The Results section should include the findings of your study and ONLY the findings of your study. The findings include:

• Data presented in tables, charts, graphs, and other figures (may be placed into the text or on separate pages at the end of the manuscript)
• A contextual analysis of this data explaining its meaning in sentence form
• All data that corresponds to the central research question(s)
• All secondary findings (secondary outcomes, subgroup analyses, etc.)

If the scope of the study is broad, or if you studied a variety of variables, or if the methodology used yields a wide range of different results, the author should present only those results that are most relevant to the research question stated in the Introduction section .

As a general rule, any information that does not present the direct findings or outcome of the study should be left out of this section. Unless the journal requests that authors combine the Results and Discussion sections, explanations and interpretations should be omitted from the Results.

How are the results organized?

The best way to organize your Results section is “logically.” One logical and clear method of organizing research results is to provide them alongside the research questions—within each research question, present the type of data that addresses that research question.

Let’s look at an example. Your research question is based on a survey among patients who were treated at a hospital and received postoperative care. Let’s say your first research question is:

“What do hospital patients over age 55 think about postoperative care?”

This can actually be represented as a heading within your Results section, though it might be presented as a statement rather than a question:

Attitudes towards postoperative care in patients over the age of 55

Now present the results that address this specific research question first. In this case, perhaps a table illustrating data from a survey. Likert items can be included in this example. Tables can also present standard deviations, probabilities, correlation matrices, etc.

Following this, present a content analysis, in words, of one end of the spectrum of the survey or data table. In our example case, start with the POSITIVE survey responses regarding postoperative care, using descriptive phrases. For example:

“Sixty-five percent of patients over 55 responded positively to the question “ Are you satisfied with your hospital’s postoperative care ?” (Fig. 2)

Include other results such as subcategory analyses. The amount of textual description used will depend on how much interpretation of tables and figures is necessary and how many examples the reader needs in order to understand the significance of your research findings.

Next, present a content analysis of another part of the spectrum of the same research question, perhaps the NEGATIVE or NEUTRAL responses to the survey. For instance:

  “As Figure 1 shows, 15 out of 60 patients in Group A responded negatively to Question 2.”

After you have assessed the data in one figure and explained it sufficiently, move on to your next research question. For example:

  “How does patient satisfaction correspond to in-hospital improvements made to postoperative care?”

This kind of data may be presented through a figure or set of figures (for instance, a paired T-test table).

Explain the data you present, here in a table, with a concise content analysis:

“The p-value for the comparison between the before and after groups of patients was .03% (Fig. 2), indicating that the greater the dissatisfaction among patients, the more frequent the improvements that were made to postoperative care.”

Let’s examine another example of a Results section from a study on plant tolerance to heavy metal stress . In the Introduction section, the aims of the study are presented as “determining the physiological and morphological responses of Allium cepa L. towards increased cadmium toxicity” and “evaluating its potential to accumulate the metal and its associated environmental consequences.” The Results section presents data showing how these aims are achieved in tables alongside a content analysis, beginning with an overview of the findings:

“Cadmium caused inhibition of root and leave elongation, with increasing effects at higher exposure doses (Fig. 1a-c).”

The figure containing this data is cited in parentheses. Note that this author has combined three graphs into one single figure. Separating the data into separate graphs focusing on specific aspects makes it easier for the reader to assess the findings, and consolidating this information into one figure saves space and makes it easy to locate the most relevant results.

Following this overall summary, the relevant data in the tables is broken down into greater detail in text form in the Results section.

• “Results on the bio-accumulation of cadmium were found to be the highest (17.5 mg kgG1) in the bulb, when the concentration of cadmium in the solution was 1×10G2 M and lowest (0.11 mg kgG1) in the leaves when the concentration was 1×10G3 M.”

Captioning and Referencing Tables and Figures

Tables and figures are central components of your Results section and you need to carefully think about the most effective way to use graphs and tables to present your findings . Therefore, it is crucial to know how to write strong figure captions and to refer to them within the text of the Results section.

The most important advice one can give here as well as throughout the paper is to check the requirements and standards of the journal to which you are submitting your work. Every journal has its own design and layout standards, which you can find in the author instructions on the target journal’s website. Perusing a journal’s published articles will also give you an idea of the proper number, size, and complexity of your figures.

Regardless of which format you use, the figures should be placed in the order they are referenced in the Results section and be as clear and easy to understand as possible. If there are multiple variables being considered (within one or more research questions), it can be a good idea to split these up into separate figures. Subsequently, these can be referenced and analyzed under separate headings and paragraphs in the text.

To create a caption, consider the research question being asked and change it into a phrase. For instance, if one question is “Which color did participants choose?”, the caption might be “Color choice by participant group.” Or in our last research paper example, where the question was “What is the concentration of cadmium in different parts of the onion after 14 days?” the caption reads:

 “Fig. 1(a-c): Mean concentration of Cd determined in (a) bulbs, (b) leaves, and (c) roots of onions after a 14-day period.”

Steps for Composing the Results Section

Because each study is unique, there is no one-size-fits-all approach when it comes to designing a strategy for structuring and writing the section of a research paper where findings are presented. The content and layout of this section will be determined by the specific area of research, the design of the study and its particular methodologies, and the guidelines of the target journal and its editors. However, the following steps can be used to compose the results of most scientific research studies and are essential for researchers who are new to preparing a manuscript for publication or who need a reminder of how to construct the Results section.

Step 1 : Consult the guidelines or instructions that the target journal or publisher provides authors and read research papers it has published, especially those with similar topics, methods, or results to your study.

• The guidelines will generally outline specific requirements for the results or findings section, and the published articles will provide sound examples of successful approaches.
• Note length limitations on restrictions on content. For instance, while many journals require the Results and Discussion sections to be separate, others do not—qualitative research papers often include results and interpretations in the same section (“Results and Discussion”).
• Reading the aims and scope in the journal’s “ guide for authors ” section and understanding the interests of its readers will be invaluable in preparing to write the Results section.

Step 2 : Consider your research results in relation to the journal’s requirements and catalogue your results.

• Focus on experimental results and other findings that are especially relevant to your research questions and objectives and include them even if they are unexpected or do not support your ideas and hypotheses.
• Catalogue your findings—use subheadings to streamline and clarify your report. This will help you avoid excessive and peripheral details as you write and also help your reader understand and remember your findings. Create appendices that might interest specialists but prove too long or distracting for other readers.
• Decide how you will structure of your results. You might match the order of the research questions and hypotheses to your results, or you could arrange them according to the order presented in the Methods section. A chronological order or even a hierarchy of importance or meaningful grouping of main themes or categories might prove effective. Consider your audience, evidence, and most importantly, the objectives of your research when choosing a structure for presenting your findings.

Step 3 : Design figures and tables to present and illustrate your data.

• Tables and figures should be numbered according to the order in which they are mentioned in the main text of the paper.
• Information in figures should be relatively self-explanatory (with the aid of captions), and their design should include all definitions and other information necessary for readers to understand the findings without reading all of the text.
• Use tables and figures as a focal point to tell a clear and informative story about your research and avoid repeating information. But remember that while figures clarify and enhance the text, they cannot replace it.

Step 4 : Draft your Results section using the findings and figures you have organized.

• The goal is to communicate this complex information as clearly and precisely as possible; precise and compact phrases and sentences are most effective.
• In the opening paragraph of this section, restate your research questions or aims to focus the reader’s attention to what the results are trying to show. It is also a good idea to summarize key findings at the end of this section to create a logical transition to the interpretation and discussion that follows.
• Try to write in the past tense and the active voice to relay the findings since the research has already been done and the agent is usually clear. This will ensure that your explanations are also clear and logical.
• Make sure that any specialized terminology or abbreviation you have used here has been defined and clarified in the  Introduction section .

Step 5 : Review your draft; edit and revise until it reports results exactly as you would like to have them reported to your readers.

• Double-check the accuracy and consistency of all the data, as well as all of the visual elements included.
• Read your draft aloud to catch language errors (grammar, spelling, and mechanics), awkward phrases, and missing transitions.
• Ensure that your results are presented in the best order to focus on objectives and prepare readers for interpretations, valuations, and recommendations in the Discussion section . Look back over the paper’s Introduction and background while anticipating the Discussion and Conclusion sections to ensure that the presentation of your results is consistent and effective.
• Consider seeking additional guidance on your paper. Find additional readers to look over your Results section and see if it can be improved in any way. Peers, professors, or qualified experts can provide valuable insights.

One excellent option is to use a professional English proofreading and editing service  such as Wordvice, including our paper editing service . With hundreds of qualified editors from dozens of scientific fields, Wordvice has helped thousands of authors revise their manuscripts and get accepted into their target journals. Read more about the  proofreading and editing process  before proceeding with getting academic editing services and manuscript editing services for your manuscript.

As the representation of your study’s data output, the Results section presents the core information in your research paper. By writing with clarity and conciseness and by highlighting and explaining the crucial findings of their study, authors increase the impact and effectiveness of their research manuscripts.

For more articles and videos on writing your research manuscript, visit Wordvice’s Resources page.

Wordvice Resources

• How to Write a Research Paper Introduction 
• Which Verb Tenses to Use in a Research Paper
• How to Write an Abstract for a Research Paper
• How to Write a Research Paper Title
• Useful Phrases for Academic Writing
• Common Transition Terms in Academic Papers
• Active and Passive Voice in Research Papers
• 100+ Verbs That Will Make Your Research Writing Amazing
• Tips for Paraphrasing in Research Papers

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here .

Loading metrics

Open Access

Peer-reviewed

Research Article

On the possible use of hydraulic force to assist with building the step pyramid of saqqara

Roles Conceptualization, Data curation, Investigation, Methodology, Project administration, Resources, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected] , [email protected]

Affiliation Paleotechnic., Paris, France

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Software, Validation, Visualization, Writing – original draft, Writing – review & editing

Affiliation Univ. Grenoble Alpes, INRAE, CNRS, IRD, Grenoble INP, IGE, Grenoble, France

Roles Conceptualization, Investigation, Methodology, Software, Visualization

Affiliation Sicame Group, Arnac-Pompadour, France

Roles Conceptualization, Investigation, Methodology, Validation, Writing – review & editing

Affiliation CEDETE—Centre d’études sur le Développement des Territoires et l’Environnement, Université d’Orléans, Orléans, France

Roles Conceptualization, Investigation, Methodology, Validation

Roles Conceptualization, Investigation, Methodology, Visualization

Affiliation AtoutsCarto, Bourges, France

Roles Methodology, Project administration

Affiliation Verilux International, Brienon-sur-Armançon, France

Roles Conceptualization, Investigation, Validation, Writing – review & editing

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Software, Validation

Roles Conceptualization, Investigation, Methodology, Supervision, Validation

• Xavier Landreau, 
• Guillaume Piton, 
• Guillaume Morin, 
• Pascal Bartout, 
• Laurent Touchart, 
• Christophe Giraud, 
• Jean-Claude Barre, 
• Cyrielle Guerin, 
• Alexis Alibert, 
• Charly Lallemand

• Published: August 5, 2024
• https://doi.org/10.1371/journal.pone.0306690
• Reader Comments

The Step Pyramid of Djoser in Saqqara, Egypt, is considered the oldest of the seven monumental pyramids built about 4,500 years ago. From transdisciplinary analysis, it was discovered that a hydraulic lift may have been used to build the pyramid. Based on our mapping of the nearby watersheds, we show that one of the unexplained massive Saqqara structures, the Gisr el-Mudir enclosure, has the features of a check dam with the intent to trap sediment and water. The topography beyond the dam suggests a possible ephemeral lake west of the Djoser complex and water flow inside the ’Dry Moat’ surrounding it. In the southern section of the moat, we show that the monumental linear rock-cut structure consisting of successive, deep compartments combines the technical requirements of a water treatment facility: a settling basin, a retention basin, and a purification system. Together, the Gisr el-Mudir and the Dry Moat’s inner south section work as a unified hydraulic system that improves water quality and regulates flow for practical purposes and human needs. Finally, we identified that the Step Pyramid’s internal architecture is consistent with a hydraulic elevation mechanism never reported before. The ancient architects may have raised the stones from the pyramid centre in a volcano fashion using the sediment-free water from the Dry Moat’s south section. Ancient Egyptians are famous for their pioneering and mastery of hydraulics through canals for irrigation purposes and barges to transport huge stones. This work opens a new line of research: the use of hydraulic force to erect the massive structures built by Pharaohs.

Citation: Landreau X, Piton G, Morin G, Bartout P, Touchart L, Giraud C, et al. (2024) On the possible use of hydraulic force to assist with building the step pyramid of saqqara. PLoS ONE 19(8): e0306690. https://doi.org/10.1371/journal.pone.0306690

Editor: Joe Uziel, Israel Antiquities Authority, ISRAEL

Received: December 7, 2023; Accepted: June 22, 2024; Published: August 5, 2024

Copyright: © 2024 Landreau et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files. The computer codes are available upon request.

Funding: The Sicame Group, The Atoutscarto Company and The Verilux Company provided support in the form of salaries for GM, CG and J-CM, respectively. The specific roles of these authors are articulated in the ‘author contributions’ section.

Competing interests: The authors have read the journal’s policy and have the following competing interests: GM, CG and J-CM are paid employees of The Sicame Group, The Atoutscarto Company and The Verilux Company, respectively. There are no patents, products in development or marketed products associated with this research to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

1 Introduction

The funerary complex of King Djoser, built at Saqqara in Egypt around 2680 B.C., is considered a significant milestone in monumental architecture. It is the first to disclose two crucial innovations: a pyramid shape for the pharaoh’s grave and the exclusive use of fully dressed stones for masonry. In practice, it is also revolutionary in the ability to extract and raise stones by millions before stacking them with precision [ 1 ]. Djoser’s complex visible achievements are such that its architect, Vizier, and Great Priest of Ra, Imhotep, was deified by the New Kingdom.

The knowledge and innovations implemented in the Djoser mortuary complex profoundly influenced future developments and were widely perfected throughout the Old Kingdom’s III rd and IV th Dynasties, i . e . circa 2680–2460 B.C. These developments resulted in a substantial increase in the megaliths’ size [ 2 ], leading to pyramids of spectacular dimensions, such as those of the Meidum, Dahshur, and Giza plateaus. In less than 150 years, the average weight of the typical large stones was thus multiplied by ≈8 and went from ≈300 kg for Djoser’s pyramid to more than 2.5 tons for Chephren’s pyramid’s structural blocks [ 3 ]. For the largest lintels, the weight increases by two orders of magnitude, with several blocks of ≈50 – 100 tons for Cheops’ pyramid. On this short timeframe on the scale of human history, Egyptians carried and raised some 25 million tons of stones [ 4 ] to build seven monumental pyramids. Assuming an annual work schedule of 300 days at a rate of 10 hours/day, meaning 450,000 hours spread over less than 150 years, this requires a technical and logistical organization capable, on average, of cutting, moving, and adjusting about 50 tons of stone blocks per hour. Even if one admits that not every pyramid’s blocks are fitted with millimeter precision, the amount of work accomplished is truly remarkable. Interestingly, the pyramids later built in Egypt tended to be smaller with time and never reached the volume of the Old Kingdom’s monumental structures again.

As authentic sources from the working sphere of pyramid architects are currently lacking, no generally accepted wholistic model for pyramid construction exists yet. Although many detailed publications dedicated to pyramid-building procedures have given tangible elements [ 5 , 6 ], they usually explain more recent, better documented, but also smaller pyramids [ 7 ]. These techniques could include ramps, cranes, winches, toggle lifts, hoists, pivots, or a combination of them [ 8 – 10 ]. Studies of the pyramid’s construction sites also revealed a high level of expertise in managing the hydraulic and hydrological environment, such as utilizing waterways to deliver materials, constructing ports and locks, or setting up irrigation systems [ 11 , 12 ]. These achievements have led some scholars to refer to ancient Egypt as an ‘early hydraulic civilization [ 11 ].’ However, there is actually very little multidisciplinary analysis combining the rich archaeological findings on pyramids with other disciplines such as hydrology, hydraulics, geotechnics, paleoclimatology, or civil engineering [ 9 ]. Therefore, the topic of water force in the context of pyramid construction remains insufficiently addressed in the academic literature.

Moreover, a second question accentuates the enigma: the Pharaohs who built these pyramids are missing. Until now, neither written record nor physical evidence reports the discovery of one of the III rd and IV th Dynasties’ Pharaohs. Old Kingdom’s ‘big’ pyramids’ rooms were allegedly plundered [ 13 – 15 ] during the millennia that followed the construction of the pyramids, leaving little evidence behind [ 12 ]. The III rd and IV th Dynasties’ rooms present little or no funerary attributes, such as those observed in other high-dignitary figures’ tombs contemporary to the period [ 16 , 17 ], with no King’s remains found inside. In addition, the walls of the pyramids’ chambers do not exhibit any hieroglyphs, paintings, engravings, or drawings, which would allow us to qualify them as funerary with certainty. Despite this lack of evidence, many authors [ 18 ] still support that these rooms can be attributed to Pharaohs’ burials mainly based on royal cartouches or Kings’ names found elsewhere within the pyramid or nearby temples.

Over the recent years, Dormion & Verd’Hurt [ 19 , 20 ], Hamilton [ 21 – 24 ] or others [ 1 , 25 ] were among the first to consider possible non-funerary functions of pyramids’ internal layouts by pointing out some architectural inconsistencies and highlighting the high degree of complexity of several structures, irrelevant for a burial chamber. Their analysis provided both chambers and gallery systems with a technical dimension, emphasizing a level of engineering on the part of the ancient builders that is quite remarkable and sometimes challenges any apparent explanation. This technical level is at once reflected in the geometry of the rooms and ducts, as well as in the stonework, which includes materials selection, extraction, cutting, and then assembling with exceptional accuracy [ 20 ]. This precision involved several advanced sub-techniques, such as inter-block mortar joint realization [ 26 – 29 ] or stone polishing with flatness and roughness values that reach levels of contemporary know-how. Apart from surfaces and interfaces, the builders’ technical ability is also evident throughout sophisticated mechanical systems set up in the pyramids [ 30 ], as swivel stone flaps’ designs in the Meidum and Bent pyramids [ 21 , 24 ] or tilted portcullises found in the Bent pyramid, as well as at Giza [ 20 ]. These elements suggest that, rather than an aesthetic rendering or a funerary use for these layouts, ancient Egyptians intended technical functions for some walls, tunnels, corridors, shafts, and chambers where more straightforward existing techniques were insufficient.

In summary, the analysis of the pyramids’ construction and the investigation of their internal layouts seem to require more research to provide a wholistic explanation to their purpose. This study aims to provide a fresh look at these topics by applying an alternative, multi-disciplinary, wholistic approach. It revisits the Old Kingdom’s pyramids’ construction methodology and seeks to explain the significance of internal layouts during construction. Based on current archaeological knowledge, we demonstrate that the Saqqara’s topography and the layout of several structures are consistent with the hypothesis that a hydraulic system was used to build the pyramid. The paper is divided into three main sections that analyze the current scientific literature to address the following inquiries: (i) Was the plateau of Saqqara supplied with water? (ii) If so, how was it possibly stored and treated? and (iii) How was it used to build the pyramid? A discussion and some concluding remarks and perspectives follow.

2 The saqqara’s hydrologic network

Our study began with the postulate that the larger Cheops’ and Chephren’s pyramids of Giza plateau were the outcomes of technical progress from previous pyramids, with the Step Pyramid as a technological precursor. While many literature studies focus on the construction of Cheops’ pyramid, we found it more relevant to examine the building techniques used for the Step Pyramid first. This would provide insight into the processes used by ancient builders that were later refined in subsequent pyramids. As a first approach, we analyzed potential reasons for the specific building of King Djoser’s Complex on the Saqqara Plateau.

2.1 Water resource from the desert wadis

Although detailed measurements of the Nile flood levels have been reported since the V th Dynasty (2480 B.C.) [ 31 – 33 ], there is very little information available about the hydrology of its desert tributaries, known as ’wadis’, in ancient Egypt. Sedimentological evidence of heavy rainfalls and flash floods exists [ 31 , 34 ] but little is known beyond that.

Determining the rainfall regime that the Saqqara region experienced about 4,700 years B.P. is challenging and uncertain. Past studies demonstrated that, from about 11,000 to 5,000 B.P, during the so-called ‘Green Sahara’ period, the whole Sahara was much wetter than today, and the landscape was savannah rather than desert [ 35 , 36 ]. Around 4500–4800 years B.P. too, the Eastern Mediterranean region was wetter than it is now, despite drying up later [ 37 – 39 ]. A range of annual precipitation value of 50–150 mm/year is assumed in the following calculation to perform crude computations of water resource. It covers the range between the >150 mm/year suggested by Kuper & Kropelin [ 40 ] for the end of the Green Sahara period, before the subsequent drier period, during which rainfall decreased to <50 mm/year. The range of variability, i . e . 50 to 150 mm/yr is also consistent with the typical inter-annual rainfall variability observed in the region [ 38 ].

Then, current hydrological monitoring on Egyptian wadis located further to the north and experiencing comparable annual rainfall ( i . e ., 100–200 mm/yr) showed that only 1–3% of this mean annual precipitation was measured as runoff, i.e., surface flows [ 41 ]. This average range is hereafter used for conservative, first-order estimations of available water volume, referred hereafter to as the ‘water resource’. Note that the infrequent, most intense events can reach 50 mm of rainfall and trigger devastating flash floods where the runoff coefficients have been measured up to 30%, i . e ., one order of magnitude higher than the mean annual [ 41 – 43 ]. Note that these water resource and flash flood hydrology estimates neglect that the soils were probably richer in clay and silt just after the Green Sahara period, with several millennia of a wetter climate and savannah landscape [ 35 , 36 ], which would increase the runoff coefficient and available surface water resource in the wadis.

2.2 The Saqqara site: a plateau with a water supply

The Saqqara necropolis is located on a limestone plateau on the west bank of the Nile River, about 180 km from the Mediterranean Sea ( Fig 1 ). The entire site lies in the desert, less than two kilometers from the plateau’s edge (elevation 40–55 m ASL— Above Sea Level ), which overlooks the Nile floodplain (height ≈ 20 m ASL). Further to the west, the desert rises gently for about 20 km (hills’ top elevation ≈ 200–300 m ASL).

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

(Satellite image: Airbus Pléiades, 2021-07-02, reprinted from Airbus D&S SAS library under a CC BY license, with permission from Michael Chemouny, original copyright 2021).

https://doi.org/10.1371/journal.pone.0306690.g001

The reasons behind the construction of the Djoser complex at Saqqara remain unclear. The contribution of economic, socio-political, and religious factors was previously highlighted [ 44 , 45 ], but environmental factors were also possibly influential. In 2020, Wong provided evidence that the climate, geology, and hydrology would have influenced building choices and may have contributed to, or perhaps accelerated, the emergence of stone architecture on the Saqqara plateau [ 37 ].

From a geological standpoint, the layered structure of the limestone at Saqqara was indeed stressed as a favorable factor for excavating large amounts of construction stones [ 46 , 47 ]. These layers, which consist of 30–60 cm thick sand-rich calcareous beds alternated with calcareous clay and marl layers, made it easy to extract the limestone blocks from their parent beds by vertical cuttings, the original thickness being reflected in the building stones’ thickness of Djoser’s complex.

From a hydrological standpoint, the Abusir wadi is considered a second environmental factor that strongly influenced the Early Dynastic development of the Saqqara necropolis at least [ 45 , 48 – 50 ]. The Abusir wadi is the ephemeral stream draining the hills west of Saqqara ( Fig 1 ) . Before this study, academic research mainly focused on the downstream part of the wadi [ 45 , 48 – 50 ], namely the Abusir Lake [ 51 ] located north of Saqqara Plateau. However, the upstream portion has remained undocumented.

In order to analyze the relationships between the Abusir wadi and the Step Pyramid’s construction project, the drainage networks west of the Saqqara area were mapped for the first time to the best of our knowledge, using various satellite imagery ( Fig 1 ) and Digital Elevation Models (see S1 Fig in S2 File ).

A paleo-drainage system can be identified upstream of the Gisr el-Mudir structure as the origin of the Abusir wadi ( Fig 1 , pink line). The boundaries of this runoff system form a catchment area never reported so far, although easily recognizable from the geomorphological imprints of surface paleochannels in the desert and on historical maps [ 52 ]. Although it currently has a 15 km 2 surface area, we cannot rule out the possibility that the drainage divides shifted and changed due to land alterations and aeolian sand deposits over the past 4,500 years.

The current catchment summit is about 110 m ASL, giving the Abusir wadi a 1% average slope over its slightly more than 6 km length. In the field of hydrology, a 1% gradient is described as ‘rather steep’. With such steep slopes, transportation of sand and gravel is expected during flashfloods, which can cause severe downstream damage (scouring or burying of structures, filling of excavations and ponding areas). In comparison, irrigation channels are rather at least ten times less steep (about 0.1%), and the Nile slope is less than 0.01% (less than 200m of elevation gain between Aswan and Cairo).

2.3 The Wadi Taflah: A possible complementary water supply

Reported since the early 1800s, a former tributary to the Nile called the Bahr Bela Ma [ 53 , 54 ] or ‘ Wadi Taflah’ flowed parallel to the Abusir wadi catchment, less than two kilometers south of the Saqqara plateau. From satellite imagery, we identified that the Wadi Taflah arises from a drainage area of almost 400 km 2 and consists of three main branches ( Fig 2 , numbered black dots) still visible from the desert’s geomorphological marks. This network is also visible on the radar imagery provided by Paillou [ 55 ] that can penetrate multiple meters of sand ( S2 Fig in S2 File ). The similarity of the optical and radar drainage patterns confirms the existence and old age of this hydrological network.

https://doi.org/10.1371/journal.pone.0306690.g002

Although no canal was detected from the satellite data, the close proximity of Abusir wadi with the Wadi Taflah ( Fig 2 ) is intriguing and raises the question about a potential ancient, artificial connection between them. According to the 18 th -century maps published by Savary [ 54 ], the Wadi Taflah was ‘closed by an ancient King of Egypt.’ Such a testimony, although imprecise, could suggest the construction of a water diversion by a former ruler. A geophysical investigation could help to find such a structure if existing. The drainage area of Wadi Taflah covers nearly 400 km 2 at an elevation >58 m ASL. This elevation is high enough to allow the diversion of the drainage area toward the Abusir wadi. This would result in an increase in the drained area and associated availability of water resources by a factor of >25 times. Based on the hydrological conditions described in section 2.1, the estimated water resource from Abusir wadi and Wadi Taflah is crudely between 7,500 to 68,000 m 3 /year and 200,000 to 1,800,000 m 3 /year, respectively.

2.4 The Abusir wadi: A structural element in the early dynastic Saqqara’s development

According to the Saqqara topography ( Fig 3 ), the Abusir wadi flowed through the Gisr el-Mudir enclosure before heading north towards the Nile floodplain, where it used to feed an oxbow lake, the Abusir Lake [ 51 ]. With such a localization, the Gisr el-Mudir walls literally dam the Abusir wadi valley’s entire width. The sparse vegetation only growing in the valley bottom upstream of Gisr el-Mudir and not elsewhere in the area evidences this damming and interception of surface and subsurface flows ( Fig 4A , green line). This slight moist area is dominated by plants commonly found in desert margins and wadis, such as Panicum thurgidum and Alhagi graecorum [ 56 ], and is typical of hypodermal flows.

Contour lines extracted from the 1:5,000 topographical map [ 52 ] “Le Caire, sheet H22”.

https://doi.org/10.1371/journal.pone.0306690.g003

a. The Gisr el-Mudir check dam (Satellite image: Airbus Pléiades, 2021-07-02, reprinted from Airbus D&S SAS library under a CC BY license, with permission from Michael Chemouny, original copyright 2021); b.: Digital Elevation Model generated from the 1:5,000 topographical map “Le Caire, sheet H22”.

https://doi.org/10.1371/journal.pone.0306690.g004

Downstream of the Gisr el-Mudir, the Abusir wadi joins the Saqqara Plateau. Its boundaries are defined to the south by an outcropping limestone ridge and to the east by the Sekhemkhet and Djoser’s enclosures ( Fig 3 ).

The landform of this area seems inconsistent with a pure fluvial formation. Instead, the very flat topography on about 2–2.5 km 2 , according to the Saqqara Geophysics Survey Project (SGSP) [ 57 – 60 ] and possibly allowed some ephemeral ponding water which may have resulted in an episodic upper Abusir lake after the most intense rainfalls. However, due to the several-meter deep wind-blown and alluvial sand cover accumulated over the past millennia [ 57 ], the riverbed altitudes during Djoser’s reign are challenging to establish without further investigations, and only broad patterns can be determined from the local topography [ 52 ].

As with many other small wadis, the Early Dynastic hydrology of the Abusir wadi remains largely unknown. According to fluvial sediment analysis in the Abusir Lake area, the Abusir wadi was probably a perennial stream during the Old Kingdom period [ 51 ]. Although the climate is hot and arid nowadays, several studies support a more humid environment during the Old Kingdom [ 34 ] . Multiple strands of evidence indeed suggest that Egypt experienced considerable rainfalls around the reign of Djoser, resulting in frequent flooding and heavy runoffs on the Saqqara Plateau. This climatic feature is supported by sedimentary deposits resulting from flowing water of ‘considerable kinetic force’ contemporary to Djoser’s reign [ 61 , 62 ] . According to Trzciński et al.[ 34 ], the strongly cemented structure L3 found in the Great Trench surrounding the Djoser Complex was due to cyclical watering while the high content of Fe3+ indicates that the region experienced intensive weathering in a warm and humid environment. In 2020, Wong concluded that the ‘ intriguing possibility that the Great Trench that surrounds the Djoser complex may have been filled with water ’ during Djoser’s reign [ 37 ]. If so, this might explain why tombs were built on the northern part of the Saqqara plateau which has a higher altitude [ 45 ] and nothing was constructed inside the Trench until the reign of Userkaf and Unas (V th Dynasty).

3. The saqqara’s water management system

3.1 the gisr el-mudir check dam.

Reported at least since the 18 th century [ 63 ] and extensively described within a decade of a geophysical survey by Mathieson et al ., see also [ 45 ] for a summary, the Gisr el-Mudir is a rectangular enclosure located a few hundred meters west of the Djoser’s complex ( Fig 3 , Fig 4A & 4B ). This monumental structure has a footprint of about 360 m x 620 m, i . e ., larger than the Djoser complex (545 m x 277 m). The walls have an estimated volume of >100,000 m 3 (SGSP, 1992–1993 report), meaning about one-third of the Step Pyramid’s volume. Field inspection and geophysical results from the SGSP [ 57 ] found no construction inside except for a couple of more recent, small graves, thus confirming that the enclosure is mainly empty. Moreover, several elements in the building suggest that this structure predated the Step Pyramid’s complex and was tentatively dated to the late II nd or early III rd Dynasty [ 57 , 64 ], which might turn it into the oldest substantial stone structure in Egypt discovered so far.

Before this study, several conflicting theories about the Gisr el-Mudir’s purpose were put forward [ 59 ]: e . g ., an unfinished pyramid complex (but the lack of a central structure made it improbable to be a funerary monument), a guarded fortress [ 65 ] protecting the Saqqara necropolis from nomadic Bedouin incursions, an embankment to raise a monument to a higher level [ 66 ], a celebration arena [ 64 , 67 ], or even a cattle enclosure. However, given the low level of exploratory work afforded to the structure, no generally accepted explanation exists yet, and its purpose has remained more conjectural than substantiated.

In light of the upstream watershed and its transversal position across the Abusir River, the Gisr el-Mudir’s western wall meets the essential criteria of a check dam, i . e ., a dam intending to manage sediment and water fluxes [ 68 , 69 ]. This comparison is particularly striking regarding its cross-section ( Fig 5 ). According to Mathieson et al . [ 59 ], the basic structure of this wall consists of a hollow construction of two rough-hewn limestone masonry skin-walls, ≈3.2 m high, separated by a 15 m interspace filled with three layers of materials extracted from the surrounding desert bedrock [ 70 ] and cunningly arranged. The first layer ( Fig 5 , ‘ A ’ dot) is made of roughly laid local limestone blocks forming a buttress against the inside of the facing blocks. The secondary fill ( B ) comprises coarse sand and medium to large limestone fragments. Then, the third fill ( C ) consists of rough to fine sand and silt, small limestone fragments, and chippings with pebble and flint nodules. Finally, these A, B, and C backfill layers are positioned symmetrically to the median axis of the wall.

Figure adapted from [ 58 ].

https://doi.org/10.1371/journal.pone.0306690.g005

Civil engineering was used during the Old Kingdom to protect settlements from flash floods, such as the Heit el-Ghurab (’Wall of the Crow’) safeguarding the village of the pyramid builders at Giza [ 71 ]. Regarding the Gisr el-Mudir structure, the abovementioned elements strikingly echo the transversal profile and slope protection of another famous Old Kingdom structure: the Sadd el-Kafara dam built on the Wadi al-Garawi , a colossal building found to be contemporary to that of the Gisr el-Mudir [ 72 – 74 ]. Both structures present the technical signature of zoned earthen dams: a wide embankment made of a central impervious core surrounded by transition filters, i . e ., filling material with coarser grain size, preventing erosion, migration, and potential piping of the core fine material due to seepage. The semi-dressed limestone walls stabilized the inner material and protected it against erosion when water flowed against and above the dam. Both dams have much broader profiles than modern dams. This oversizing could be due to the unavailability of contemporary compaction systems or an empirical and conservative structural design. They both have narrower cores of fine material at the bottom of the dam than at their crest, contradicting modern design [ 75 ]. This can be attributed to the construction phasing that would have started by raising the sidewalls buttressed against the coarse and intermediate filling ( B and C fills in Fig 5 ), followed by a phase of filling the wide core with finer, compacted material [ 72 ].

Finally, the eastern wall’s north-south profile ( Fig 6 , line A-B ) presents a parabolic profile relevant to guide the flows to the basin’s center formed by Gisr el-Mudir. This guidance would have prevented the dam failure by outflanking during flooding events when the dam outlet was saturated. We estimate that the accumulated water crossed the dam through an outlet likely located at the valley’s lowest elevation, i . e ., near 48.7 m ASL ( G1 in Figs 4B and Fig 6 ). In summary, the Gisr el-Mudir’s western wall likely acted as a first check dam to the Abusir wadi flows.

https://doi.org/10.1371/journal.pone.0306690.g006

The excavations performed on the eastern wall of the Gisr el-Mudir highlighted a lower structural quality [ 45 ]. Its shape is similar to that of the western wall, with a distinctive parabolic profile ( Fig 6 , line C-D ). Furthermore, it discloses two topographical singularities: first, its overall altitude is a few meters lower than the western wall ( Fig 7A ). Then, in the southern part of the eastern wall, a geophysics anomaly ( G2 in Figs 4B and Fig 6 ) was found to be a series of massive, roughly cut, ‘L’-shaped megaliths [ 45 , 66 ]. Before our study, these megaliths were thought to possibly be the remains of a monumental gateway–due to their similarities with the Djoser’s complex enclosure’s entrance–but their purpose was not specified [ 66 ]. According to our analysis, these megaliths could be the side elements of the water outlets, possibly slit openings [ 76 ] that were likely closed off by wood beams but could be opened to drain the basin. They are consistently found near a trench that is 2.2 m deep [ 45 ], which we believe is possibly the canal that guided outflowing water. In a nutshell, the eastern wall likely acted as a second check dam to the Abusir flows.

a. West-east elevation profile of the Gisr el-Mudir structure. b: Schematic reconstitution of the profile with water flow.

https://doi.org/10.1371/journal.pone.0306690.g007

In addition to the two dams formed by the western and eastern walls, the Gisr el-Mudir enclosure forms a basin ( Fig 4 ). It is closed to the north by another wall made of limestone blocks, though not very tall (likely <2m) because it is built on a natural ridge [ 45 ]. The basin’s southern boundary is also mostly made of a natural ridge. The possible absence of a masonry wall on certain portions on this side was unexplained by previous analyses [ 45 ]. However, it makes perfect sense when considering a reservoir function. Anchoring dams against side slopes is indeed the standard approach to guide flows and prevent outflanking [ 68 ].

In essence, the Gisr el-Mudir enclosure exhibits the defining features of a check dam ( Fig 7B ). The catchment it intercepts is large enough (15 km 2 ), plus eventual water derivation from the Wadi Taflah to produce flash floods transporting significant amounts of gravel, sand, mud, and debris due to its slope during intense rainfalls. The valley upstream of the western wall likely served as a first reservoir where the coarsest gravels tended to deposit. The overflowing water then filled the inner basin of the Gisr el-Mudir, where coarse sand would again deposit. Assuming a storage depth between 1 and 2 meters, the retention capacity of the basin would be approximately 220,000–440,000 m 3 . This volume is in line with the overall water volume of a flash flood that could be produced by the Abusir wadi, which is estimated to be about 75,000–225,000 m 3 , assuming 50 mm of rainfall and a 0.30 runoff coefficient. This key, first structure of the Saqqara hydraulic system would have then delivered clear water downstream in normal time, as well as muddy water with an eventually suspended load of fine sand and clay during rainfall events.

3.2 The deep Trench’s water treatment system

3.2.1 general configuration..

The Djoser’s Complex is surrounded by a vast excavation area, commonly referred to as the ’Dry Moat’ since Swelim spotted its outlines [ 77 , 78 ] ( Fig 3 , blue strip). The Dry Moat is alleged to be a continuous trench cut in the bedrock, up to 50 m wide and ≈3 km long, enclosing an area of ≈600 m by ≈750 m around the Djoser complex [ 77 , 79 , 80 ]. When considering an average depth of 20 m for the four sides of the trench [ 61 ], the total excavated volume is estimated at ≈3.5 Mm 3 , approximately ten times the Step Pyramid‘s volume. Due to the thick cover of sand and debris [ 61 ] accumulated over the past millennia, its precise geometry is incompletely characterized. The moat’s east and south channels are particularly debated [ 61 ].

According to Swelim, the moat’s south channel probably split into two parts, known as the Inner and Outer south channels [ 78 ] ( Fig 8 , blue strips). The Inner south channel is relatively shallow (5–7 m deep), 25–30 m wide, and spans approximately 350 m parallel to the southern wall of Djoser’s complex.

Water from the Abusir Lake can follow two parallel circuits.

https://doi.org/10.1371/journal.pone.0306690.g008

The ‘Deep Trench’ [ 81 ] ( Fig 8 , red rectangles and dotted lines) is built inside the Inner south channel, along its south wall. It is a ≈27 m-deep, 3 m-wide, and hundreds of meter-long rock-cut channel with several ‘compartments’. So far, only about 240 m [ 78 ] of its probable 410 m length have been subject to archaeological excavations in 1937–1938 [ 78 ], 1937–1945 [ 81 ], and 1975 [ 82 ]. Consequently, approximately 170 m remains unexplored, mainly due to the presence of the later Old Kingdom two groups of mastabas built above the trench and at risk of collapse if submitted to underground excavation (transparent grey parts in Fig 8 ).

Generally, two leading theories are highlighted in the literature to explain the purpose of the trench: (i) a quarry for the Djoser’s complex [ 47 , 83 ], or (ii) a spiritual function [ 78 , 84 , 85 ]. However, over recent years, authors have pointed out several specificities in the trench’s architectural layout, which seem irrelevant in a religious or mining context [ 1 , 86 , 87 ]. In particular, on the mining aspect, several authors estimate [ 45 , 86 ] that the form of the track suggests that the extraction of stones was not its sole or even primary function, as it does not match with the ancient Egyptian quarrying methods. Reader also considers that some parts of the trench which are ~27 m deep and covered with a rocky ceiling, are wholly unrealistic for quarrying operations and unlikely to have required the paving found near the trench’s bottom [ 45 ]. This point is further emphasized by the narrow width of the excavated Deep Trench (3m), which is impractical in a mining scenario.

On the spiritual aspect, Kuraszkiewicz suggests that the trench may have developed a ritual significance as a gathering place for the souls of the nobles to serve the dead King [ 86 ]. Monnier [ 1 ] considers that the discovery of several niches in the channel does not fully demonstrate the moat’s religious purpose and considers it secondary. The trench’s ritual significance is also regarded as secondary by Reader [ 45 ], who suggests the ritual aspects developed only after the complex’s construction and do not reflect the original function of the structure.

In 2020, based on the archaeological, geological, and climatic evidence, Wong was the first to introduce the idea that the trench may have had a completely different function, being filled with runoff water following downpours [ 37 ]. If so, this would explain why it was not until the reigns of Unas and Userkaf (V th Dynasty) that new graves occupied the moat. The onset of drier climatic conditions [ 31 , 88 ] around the end of the IV th Dynasty would have created more favorable conditions for new constructions inside the moat. Despite the potential impact of Wong’s assumption, it did not receive much attention in the literature. Nonetheless, the current authors believe that Wong’s conclusions make sense when considering Saqqara’s downstream localization of a watershed.

3.2.2 The deep Trench: A series of rock-cut compartments built in a hydrological corridor.

The Inner south channel and the Deep Trench are built inside the Unas Valley, a hydrological corridor connecting the Abusir wadi plain to the Nile floodplain ( Fig 3 ). Both were thus possibly submitted to (un)controlled flooding [ 34 , 61 ] from the Abusir wadi plain.

The Deep Trench connects at least three massive subterranean compartments [ 45 , 47 ] ( Fig 8 , red parts) meticulously carved out with precisely cut surfaces [ 78 ] ( Fig 9 ) and joined by a tunnel [ 77 ] . A fourth compartment, retroactively named compartment-0 ( Fig 10 ), likely exists [ 45 , 78 ]. On a large scale, the perfect geometric alignment of these compartments is remarkable, as well as their parallelism with the Djoser’s complex and their bottom level similar to those of the southern and northern shafts (≈27 m ASL). These spatial relationships have led some authors to consider that the trench was created as a part of Djoser’s Complex [ 86 , 89 , 90 ]. This assumption has been reinforced by Deslandes’ discoveries of at least two east-west pipes, about 80 m long, connecting the Djoser’s Complex’s subterranean layouts to the Dry Moat’s eastern side [ 91 ].

a: View from the west; b: View from the east. The workers in the background provide a sense of the structure’s immense scale and technicity.

https://doi.org/10.1371/journal.pone.0306690.g009

View of the south face.

https://doi.org/10.1371/journal.pone.0306690.g010

Taken together, the Deep Trench architecture highlights technical proficiency and suggests that the ancient Egyptians intended a technical function rather than a spiritual one. Surprisingly, despite the available clues, the Deep Trench has never undergone detailed engineering studies to analyze its features and identify its purpose. The following sections suggest a hydraulic rationale behind the trench’s internal layout (more details in the Supplement ).

3.2.3 Consistency of the Deep Trench architecture with a water treatment system.

Being largely described in the literature [ 77 , 86 , 92 ] , the compartments’ layouts are presented in detail in the Supplement . Considering its architecture and geographical location, the Dry Moat’s southern section combines the technical requirements of a water treatment system, including sedimentation, retention, and purification. Fig 10 illustrates a comprehensive outline of the installation’s functioning process. Similarly to the Gisr el-Mudir, we found that the Deep Trench compartments likely served to transfer water with low suspended sediment concentration to the downstream compartments by overflowing. The process of using a series of connected tanks to filter water and remove sediment is an ancient technique that has been extensively documented in archaeological and scientific literature [ 93 – 96 ]. This method has been employed for centuries to clean water and has played a significant role in the development of water treatment practices.

Compartment-0 presents the minimum requirements of a settling basin (considerable length and width, low entry slope, position at the entry of Unas hydrological corridor) whose purpose is to facilitate the coarse particles’ settling that would overflow from Gisr el-Mudir during heavy rainfalls. The descending ramp along the south wall identified by Swelim [ 97 ] may have permitted workers to dredge the basin and remove the accumulated sediments along the east wall ( Fig 10 ) . The very probable connection [ 45 , 97 ] between compartment-0 and compartment-1, blocked with rough masonry ( Fig 9B and S3 Fig in S2 File ), is consistent with an outlet overflowing structure. Additionally, when the flow rate in compartment-0 was too high, the tunnel or even the northern portion of the trench may have been used as a spillway bypass to evacuate excess water toward the eastern portion of the Unas wadi valley ( Fig 8 , safety circuit).

Compartment-1 is then consistent with a retention basin with > 3000 m 3 capacity ( Fig 10 , left part). The bottom stone paving with mortar joints probably limited water seepage through the bedrock. Its eastern end could go until the compartment-2 [ 45 ] to form a single compartment, but this point remains debated [ 78 , 97 ] .

Compartment-2’s is, unfortunately, largely unexplored ( Fig 10 ). Its downstream position might indicate a second retention basin or possibly an extension [ 45 ] of the first one. The western part of this compartment (stairs area) perfectly aligns with the base levels of the Djoser’s complex south and north shafts, which points towards a connection between the three [ 86 ] . If so, it would be aligned with the recently discovered pipe of a 200 m-long tunnel linking the bottom of Djoser’s Complex’s southern and northern shafts [ 91 ] (see next section, Fig 11 ). Compartment-2 would then be another, or an extended, retention basin equipped with a water outlet toward the north.

https://doi.org/10.1371/journal.pone.0306690.g011

Compartment-3 ( Fig 10 , right part) is likely a side purification basin for drinking water. Its position as an appendix of the primary water circuit connecting Gisr el-Mudir to Djoser’s complex seems optimal to minimize water circulation and maximize water-settling time, thus increasing its purification. The second and third sections likely allowed further settling of particles and would have served as reservoirs during dry periods. The relatively smooth walls of the whole structure would have hindered the growth of microbes, plants, and other contaminants, thereby helping maintain the water’s cleanliness [ 98 ] . Four surface wells allowed access to the end of the last compartment where the water, kept clear and fresh in the shadow of this subterranean monumental cistern, could be used by the building site workforce [ 99 ] .

The excavated volume of the Deep Trench is greater than 14,000 m 3 [ 77 , 86 , 92 ]. If we assume that most of the water available in the Wadi Taflah was diverted toward Saqqara, this volume could be filled about a dozen to more than one hundred times per year on average. We hypothesize a typical filling level of 45 m ASL in the Deep Trench, but an accurate topographical survey is lacking, and the maximum water level could vary between 40–52 m ASL, according to the surrounding terrain elevation.

In essence, we discovered and highlighted for the first time that the Deep Trench’s position and design are consistent with possible use as a water treatment and storage system capable of cleaning and storing thousands of cubic meters of water.

4. The central hydraulic lift system

4.1 overview of the djoser’s complex’ substructure.

The internal and external architecture of the Djoser’s Complex is thoroughly documented [ 1 , 3 , 100 , 101 ]. The Supplement provides an overview of this structure. Basically, the six-step Step Pyramid itself stands slightly off-center in a rectangular enclosure toward the south and reaches a height of approximately 60 m ( Fig 11 ). The pyramid consists of more than 2.3 million limestone blocks, each weighing, on average [ 2 ], 300 kg, resulting in a total estimated weight of 0.69 million tons and a volume of ≈330,400 m 3 .

The substructure features at least 13 shafts, including two significantly sizeable twin shafts located at the north and south of the complex ( Fig 11 , insets 3&4), and an extensive and well-organized network of galleries descending up to 45 m below ground level [ 102 ]. The north shaft is surrounded by four comb-shaped structures distributed on each side and angled 90° apart. Ground Penetrating Radar (GPR) revealed that the twin shaft layouts are connected [ 91 , 102 ] by a 200 m-long tunnel. Moreover, at least two of the twelve shafts on the pyramid’s east side are connected to the supposed eastern section of the Dry Moat by two 80 m long pipes ( Fig 11 and Supplement ).

From our 3D models, we estimate that ancient architects extracted more than 30,000 tons of limestone from the bedrock to dig the whole underground structure. The total length of the tunnels and subterranean rooms combined is ~6.8 km. However, its layout and purpose remain primarily poorly known and debated [ 6 ].

4.2 The connected twin shafts

The ‘north shaft’ is located under the pyramid of Djoser and is almost aligned with its summit. This shaft is ≈28 m deep and has a square shape with 7 m sides. Its bottom part widens to ≈10 m on the last, deepest 6 m, forming a chamber ( Fig 12 and S6 Fig in S2 File ). On its upper part, the shaft extends above the ground level by at least four meters inside the Step Pyramid in the shape of a hemispherical vault that was recently reinforced ( Fig 11 , inset 5 ). This upper part inside the pyramid body remains unexplored. However, as noticed by Lauer, the shaft sides above ground level display comparable masonry to that of the southern shaft, indicating a possible upward extension [ 3 ]. On the pyramid’s north side, a steep trench with stairs provides access to the shaft.

a.: Granite box of Djoser’s complex north shaft serving as an opening-closing system for the water flow coming from side tunnels -source: [ 113 ]. b.: Limestone piles supporting the box - source: [ 3 ]. c: Diagram of the North Shaft plug system. Redrawn from Lauer sketches [ 108 ].

https://doi.org/10.1371/journal.pone.0306690.g012

The ‘south shaft’ is located ~200 m south of the north shaft, close to the Deep Trench ( Fig 11 , inset 1 ). Its dimensions and internal layout are broadly similar to the north shaft’s. The substructure of the south shaft is entered through a west-facing tunnel-like corridor with a staircase that descends about 30 m before opening up inside the shaft. The staircase then continues east and leads to a network of galleries whose layout imitates the blue chambers below the Step Pyramid. As mentioned earlier, a 200 m-long tunnel connects the lower part of the north and south shafts ( Fig 11 , orange pipe). A series of deep niches located on the south face of the south shaft [ 97 ], the shape of which resembles that of the Deep Trench’s compartments 1 and 2, might indicate a former connection between both. This point remains to be confirmed by additional investigation.

The south shaft is connected to a rectangular shaft to the west via a tunnel-like corridor with a staircase that descends approximately 30 meters before opening up into the south shaft ( Fig 11 , inset 2 ). At the corridor level, a chamber has been cut into the bedrock parallel to the descending passage [ 3 ], towards the south. This chamber features several incompletely excavated niches on its south wall, which could extend under the south wall of the Djoser complex ( Fig 8 ). Pending further excavations, they might indicate a connection with the Deep Trench.

4.3 The twin shafts’ internal layout: two plug-systems topped with maneuvering chambers

The initial purpose of the twin shafts’ granite boxes has been largely debated [ 15 , 100 ]. The presence of two shafts with two similar granite boxes and almost identical substructures was previously explained as a separation of the body and spirit of Djoser [ 100 ]. However, the Pharaoh’s body is actually missing and was not found during modern excavations. Several authors and explorers excluded the possibility of King Djoser’s burial in the north shaft [ 15 , 103 ]. Vyse claimed [ 15 ] that the box’s internal volume was too narrow for moving a coffin without breaking the body. Firth and Quibell considered [ 103 ] the fragments found by Gunn and Lauer [ 104 ] to be of mummies of ‘late date’, possibly belonging to the Middle or New Kingdom. Finally, a thorough radiocarbon dating [ 105 ] on almost all retrieved remains [ 104 , 106 , 107 ] located near the granite box excluded the possibility that ‘ even a single one of them ’[ 105 ] could have belonged to King Djoser. Therefore, although the northern shaft had clear funerary significance much later, its original purpose during the time of Djoser may have been different.

Unfortunately, the main part of the materials that filled the twin shafts was removed during past archaeological excavations, mainly in the 1930s [ 108 ], leaving only the two granite boxes at their bottom ( Fig 11 , insets 3 and 4 ). Therefore, the shafts’ internal layout description is mainly based on the explorers’ archaeological reports and testimonies[ 109 – 111 ].

The two granite boxes are broadly similar in shape and dimensions. Both are made of four layers of granite blocks and present top orifices closed by plugs that weigh several tons ( Fig 12A ). The southern box is slightly smaller, with a plug made of several pieces, making it less versatile. The north box does not lay directly on the underlying bedrock but is perched on several piles of limestone blocks supporting the lower granite beams ( Fig 12B ), tentatively attributed to robbers by Lauer [ 3 ]. The space around the box is connected with four tunnels arranged perpendicularly on each side of the shaft (see Supplement ). This space was filled with several successive layers [ 108 ] ( Fig 12C , grey parts). The lowermost layer consisted of coarse fragments of limestone waste and alabaster, making it permeable. Meanwhile, the upper layer, going up to the box ceiling’s level, was made of limestone jointed with clay mortar [ 108 ], i . e ., less permeable [ 112 ]. This ceiling was itself covered by a 1.50 m thick layer of alabaster and limestone fragments plus overlying filling ( Fig 12C , blue part), except around the plug hole, which was encircled by a diorite lining, a particularly solid rock ( Fig 12C , green part).

Directly above the granite boxes were ‘maneuvering chambers [ 108 ]’ that enabled the plug to be lifted. The plug closing the north shaft’s box has four vertical side grooves, 15 cm in diameter, intended for lifting ropes ( Fig 12C ) and a horizontal one, possibly for sealing. Below the chamber ceiling and just above the orifice, an unsheathed wooden beam was anchored in the east and west walls ( Fig 12C ). This beam likely supported ropes to lift the plug, similar to those found in the south shaft with friction traces [ 108 ].

Interestingly, the granite stones forming the granite box ceiling were bounded by mortar ( Fig 12A ), creating an impermeable barrier with the shaft’s lower part and leaving the plug’s hole as the only possible connection between the shaft and the inside of the box. Conversely, most joints between the box’s side and bottom stones, connected with the permeable bottom layer, were free from mortar.

These details, thoroughly documented during Lauer’s excavation [ 3 , 108 ] and visible on pictures ( Fig 12A and 12B ), clearly point to technical rather than symbolic application. Taken together, the granite box’s architecture and its removable plug surrounded by limestone clay-bound blocks present the technical signature of a water outlet mechanism.

When opened, such a plug system would have allowed the north shaft to be filled with water from the Deep Trench or, in another scenario, from the Dry Moat’s eastern section. The permeable surrounding filling would have permitted water discharge control from the four side tunnels. Then, the water could only seep through the granite box’s lower joints. This design would have prevented water from rushing through the system at high speed and with pressure shocks.

Considering water coming from the Deep Trench (elevation delta: 10–20 m), the retaining walls and the many layers’ cumulated weight stacked over the granite box acted as a lateral blockage and would have prevented the box ceiling from being lifted due to the underlying water pressure.

4.4 Consistency of the internal architecture of the Djoser’s complex with a hydraulic lift mechanism

After gathering all the elements of this study, we deduce that the northern shaft’s layout is consistent with a hydraulic lift mechanism to transport materials and build the pyramid. Elements at our disposal indicate that the south and north shafts could be filled with water from the Dry Moat. A massive float inside the north shaft could then raise stones, allowing the pyramid’s construction from its center in a ‘volcano’ fashion ( Fig 13 ).

https://doi.org/10.1371/journal.pone.0306690.g013

Although a connection between the Compartment -2 and the Djoser shafts has yet to be identified, it is highly probable that sediment-free water from the Deep Trench was used in this system ( Fig 13 , disk ‘ 1 ’). This water quality would have reduced the risk of fouling and malfunction because it minimizes the presence of sand and clay that feed into the north shaft. This would prevent the deposition and progressive filling in the tunnels and connections, as well as the clogging of the joints between the bottom and side granite blocks of the box. The 200 m-long underground pipe [ 91 ] that connects the north and south shafts is then consistent with the transfer of water from the Deep Trench’s water treatment system to the north shaft, possibly via the south shaft.

Furthermore, there is a proven connection between the tunnels surrounding the north shaft and the Dry Moat through the Deslandes’ pipes [ 91 ] on the eastern side of the complex ( Figs 11 and 13 ). Pending further investigation, we hypothesize that the water inlet was located to the south ( Fig 13 , disk ‘ 1 ’), with the outlet(s) sending water toward the east through two juxtaposed pipes (disk ‘ 2 ’). Several horizontal galleries connected to these two pipes were acacia-cased [ 3 ], a technique commonly used to safeguard the walls in hydraulic works in ancient Egypt. A large stone portcullis [ 108 ] found in one of these galleries may have served as a versatile gate closed during the water filling of the north shaft.

In another scenario, the Deslandes’ juxtaposed pipes ( Fig 13 , disk ‘ 2 ’) could be considered as a water inlet for unfiltered water.

Finally, we hypothesize that a hydraulic lift, a massive float that was possibly made of wood and weighed several tons (see Supplement ), should run slowly inside the shaft to prevent instabilities and friction with the sides. The stones could have been elevated by filling and emptying cycles, allowing the lift to move up and down with stones ( Fig 13 ). These stones could have passed along the northern entrance until the central shaft. Recent discoveries have shown that this gallery was kept open until the very end of the pyramid’s construction, after which it was closed [ 1 , 91 ]. In our scenario, the stones could have been transported directly at ground level, corresponding to the pyramid’s first course, or slightly higher through a ramp penetrating in a (currently sealed) corridor some meters above the ground level. This configuration would have had the particular advantage of minimizing the elevation gain for which the hydraulic lift would be required. The stones could have been transported via the so-called ‘Saite gallery [ 114 ]’ in a final scenario. Although Firth [ 114 ] considers this gallery to postdate the III rd Dynasty, it remains possible that it was recut on the basis of an earlier gallery.

4.5 Modelling the hydraulic lift mechanism

We developed a simple numerical model of the hydraulic lift to study its water consumption and loading capacity (see Supplement ). The model was kept as simple as possible to be easily checked and only intended to give relevant orders of magnitudes.

The hydraulic lift is modelled as a float loaded with stones to build the pyramid and with a vertical extension to raise this material at the necessary level. Based on the initial altitude of the lift, Z m , which cannot be below 17m from ground level (the bottom of the shaft was filled with the box and overlying rocks, see Fig 12C ), and assuming a loading of the material on the lift at the ground level, the maximum height that can be reached in one cycle is <17m. To achieve greater heights, we hypothesize that the lift platform was blocked during the float descent, e . g ., using beams (see Fig 14 ). This modification would have allowed the platform to reach higher altitudes by adding or unfolding an extension. For the top of the pyramid, the float could be conversely used as a counterweight when descending, pulling on ropes that would haul the platform after passing over pulleys above the shaft head. A dual-use method involving hauling during shaft draining and elevating during water filling would have been the optimal management approach.

The lift platform (red line), and extension support (orange line) during the unfolding of the lower element are represented. The associated holes are to be localized in further excavation of the upper part of the shaft.

https://doi.org/10.1371/journal.pone.0306690.g014

The beginning of the pyramid building was most probably performed using ramps prolonging the path from the local quarry, possibly the Dry Moat [ 44 ]. To provide an upper bound of water consumption, we modelled the pyramid building using the hydraulic lift from the first layer at ground level. Our model suggests that this upper bound value is 18 Mm 3 of water required to build the whole pyramid using the float to lift stones only when the shaft is filled (see Supplement ). A few million were required to build the first 20 m and could be saved if ramps were used instead. The total amount of water needed would have been reduced by about one-third if the float had been used as a counterweight, pulling on ropes to haul stones on a platform suspended in the top part of the shaft rather than being located on a wooden frame extension attached to the float. Finally, if both lifting (when filling the shaft) and hauling (when draining the shaft) were used, the water consumption would decrease by two-thirds. If the loading was not performed at ground level but rather through a ramp and gallery above ground level, about one-quarter of the water would be saved if, for instance, using a 5 m-high ramp and 43% for a 10 m-high ramp. Further investigation above the vault and on the pyramid sides could help to identify such an eventual gallery. If, conversely, the loading was performed about 13 m below ground level in the top part of the northern gallery ( S6 Fig in S2 File ), the water consumption would typically increase by two-thirds.

On the other hand, through our research and calculations, we have determined that the Wadi Taflah catchment had the capacity to supply 4–54 Mm 3 over 20–30 years of construction, therefore not enough when assuming only pessimistic values (lower bound for rainfall and runoff coefficient, fast construction and sub-optimal use of the lift just using it when water rose), but sufficient when assuming intermediate values, and eight-times enough water to meet this demand when assuming optimistic values (upper bounds of parameters and dual lifting-hauling functioning). If further research demonstrates that the higher clay and silt content possibly present at that time shortly after the Green Sahara period probably led to increased runoff coefficients by a factor of 2–3 or even more, the resource would be increased by the same factor.

The climatological conditions on the Saqqara plateau during the III rd Dynasty are still not well understood [ 37 ]. As a first assumption, we estimate that the water supply may have been continuous even without an upper Abusir lake’s permanent existence, thanks to the flow from the wadi Abusir and, more significantly, through a probable derivation system from the nearby Wadi Taflah, assuming this large catchment had a more perennial runoff regime. Pedological investigations would be worthwhile in the plateau area and in the talweg of both wadis to look for evidence of more frequent water flow.

As a result, the hydraulic mechanism may have only been usable when sufficient water supply was available, so it may have only been used periodically. Other techniques, such as ramps and levees, were likely used to bring the stones from the quarries and adjust their positions around the lifting mechanism or when it was not in operation.

5. Discussion

A unified hydraulic system.

Based on a transdisciplinary analysis, this study provides for the first time an explanation of the function and building process of several colossal structures found at the Saqqara site. It is unique in that it aligns with the research results previously published in the scientific literature in several research areas: hydrology, geology, geotechnics, geophysics, and archaeology. In summary, the results show that the Gisr el-Mudir enclosure has the feature of a check dam intended to trap sediment and water, while the Deep Trench combines the technical requirements of a water treatment facility to remove sediments and turbidity. Together, these two structures form a unified hydraulic system that enhances water purity and regulates flow for practical uses and vital needs. Among the possible uses, our analysis shows that this sediment-free water could be used to build the pyramid by a hydraulic elevator system.

By its scale and level of engineering, this work is so significant that it seems beyond just building the Step Pyramid. The architects’ geographical choices reflect their foresight in meeting various civil needs, making the Saqqara site suitable for settling down and engaging in sedentary activities, such as agriculture, with access to water resources and shelter from extreme weather conditions. This included ensuring adequate water quality and quantity for both consumption and irrigation purposes and for transportation, navigation, or construction. Additionally, after its construction, the moat may have represented a major defensive asset, particularly if filled with water, ensuring the security of the Saqqara complex [ 115 ].

The hydraulic lift mechanism seems to be revolutionary for building stone structures and finds no parallel in our civilization. This technology showcases excellent energy management and efficient logistics, which may have provided significant construction opportunities while reducing the need for human labor. Furthermore, it raises the question of whether the other Old Kingdom pyramids, besides the Step Pyramid, were constructed using similar, potentially upgraded processes, a point deserving further investigation.

Overall, the hydraulic lift could have been a complementary construction technique to those in the literature for the Old Kingdom [ 8 , 10 ]. Indeed, it is unlikely that a single, exclusive building technique was used by the ancient architects but that a variety of methods were employed in order to adapt to the various constraints or unforeseen circumstances of a civil engineering site, such as a dry spell. Therefore, the beginning of the pyramid building was most probably performed using ramps prolonging the path from the local quarry. According to petrographic studies [ 47 ], the main limestone quarry of the Saqqara site could correspond to the Dry Moat that encircles the Djoser Complex, providing access on the four sides of the pyramid for the extracted blocks and reducing the average length of the ramps.

An advanced technical and technological level

By their technical level and sheer scale, the Saqqara engineering projects are truly impressive. When considering the technical implications of constructing a dam, water treatment facility, and lift, it is clear that such work results from a long-standing technical tradition. Beyond the technical aspects, it reflects modernity through the interactions between various professions and expertise. Even though basic knowledge in the hydraulics field existed during the early Dynastic period, this work seems to exceed the technical accomplishments mentioned in the literature of that time, like the Foggaras or smaller dams. Moreover, the designs of these technologies, such as the Gisr el-Mudir check-dam, indicate that well-considered choices were made in anticipation of their construction. They suggest that the ancient architects had some empirical and theoretical understanding of the phenomena occurring within these structures.

…questioning the historical line

The level of technological advancement displayed in Saqqara also raises questions about its place in history. When these structures were built remains the priority question to answer . Were all the observed technologies developed during the time of Djoser, or were they present even earlier? Without absolute dating of these works, it is essential to approach their attribution and construction period with caution. Because of the significant range of techniques used to build the Gisr el-Mudir, Reader estimates [ 70 ] that the enclosure may have been a long-term project developed and maintained over several subsequent reigns, a point also supported by the current authors. The water treatment facility follows a similar pattern, with the neatly cut stones being covered and filled with rougher later masonry. Finally, the Djoser Step Pyramid also presents a superposition of perfectly cut stones, sometimes arranged without joints with great precision and covered by other rougher and angular stones [ 3 ]. Some of these elements led some authors [ 6 , 100 ] to claim that Djoser’s pyramid had reused a pre-existing structure.

Some remaining questions

The Deep Trench was intentionally sealed off at some point in history, as evidenced by the pipe blockage between Compartment-0 and Compartment-1. The reasons are unknown and speculative, ranging from a desire to construct buildings (such as the Khenut, Nebet, or Kairer mastabas) above the trench to a technical malfunction or shutdown due to a water shortage. This sealing might also have been done for other cultural or religious purposes.

The current topography of the land around the Djoser complex, although uncertain given the natural or anthropogenic changes that have occurred over the last five millennia, does not support the existence of a trench to the east side. Therefore, our observations join those of Welc et al. [ 61 ] and some of the first explorers [ 63 ], reasonably attributing only three sections to the Dry Moat.

6 Materials and methods

• High-resolution commercial satellite images (Airbus PLEIADES, 50 cm resolution) and digital elevation models (DEM) were computed and analyzed to identify Abusir wadi’s palaeohydrological network impact on Djoser’s construction project. The processing sequence to generate DEM was mainly achieved using the Micmac software [ 116 ] developed by the French National Geographic Institute (IGN) and the open-source cross-platform geographic information system QGIS 3 . 24 . 3 . Tisler .
• Geospatial data analysis was performed using the open-source WebGL-based point cloud renderer Potree 1.8.1 and QGIS 3 . 24 . 3 . Tisler .
• The 2D CAD profiles of the Step Pyramid Complex presented throughout this article were produced using Solidworks 2020 SP5 (Dassault Systems) , Sketchup Pro 2021 (Trimble) , Blender (Blender Foundation) , and Unreal Engine 5 (Epic Games) , mainly based on dimensions collected by successive archaeological missions during the last two centuries reported in the literature.
• The Wadi Taflah watershed and the catchment area west of Gisr el-Mudir have been identified and characterized using QGIS 3 . 24 . 3 . This was done with the help of the Geomeletitiki Basin Analysis Toolbox plugin, developed by Lymperis Efstathios for Geomeletitiki Consulting Engineers S . A . based in Greece.
• The modeling of the hydraulic lift mechanism was performed using the open-source programming software RStudio 2022 . 07 . 2 .

7. Concluding remarks and perspectives

This article discloses several discoveries related to the construction of the Djoser complex, never reported before:

• The authors presented evidence suggesting that the Saqqara site and the Step Pyramid complex have been built downstream of a watershed. This watershed, located west of the Gisr el-Mudir enclosure, drains a total area of about 15 km 2 . It is probable that this basin was connected to a larger one with an estimated area of approximately 400 km 2 . This larger basin once formed the Bahr Bela Ma River , also known as Wadi Taflah , a Nile tributary.
• Thorough technical analysis demonstrates that the Gisr el-Mudir enclosure seems to be a massive sediment trap (360 m x 620 m, with a wall thickness of ~15 m, 2 km long) featuring an open check dam. Given its advanced geotechnical design, we estimate that such work results from a technical tradition that largely predates this dam construction. To gain an accurate understanding of the dam’s operating period, the current authors consider it a top priority to conduct geological sampling and analysis both inside and outside the sediment trap. This process would also provide valuable information about the chronological construction sequence of the main structures found on the Saqqara plateau.
• The hydrological and topographical analysis of the dam’s downstream area reveals the potential presence of a dried-up, likely ephemeral lake, which we call Upper Abusir Lake, located west of the Djoser complex. The findings suggest a possible link between this lake and the Unas hydrological corridor, as well as with the ‘Dry Moat’ surrounding the Djoser complex.
• The ‘Dry Moat’ surrounding the Djoser complex is likely to have been filled with water from the Upper Abusir Lake, making it suitable for navigation and material transportation. Our first topographical analysis attributes only three sections to this moat (West, North, and South).
• The Dry Moat’s inner south section is located within the Unas hydrological corridor. The linear rock-cut structure built inside this area, called ‘Deep Trench,’ consisting of successive compartments connected by a rock conduit, combines the technical requirements of a water treatment system: a settling basin, a retention basin, and a purification system.
• Taken as a whole, the Gisr el-Mudir and the Deep Trench form a unified hydraulic system that enhances water purity and regulates flow for practical uses and vital needs.
• We have uncovered a possible explanation for how the pyramids were built involving hydraulic force. The internal architecture of the Step Pyramid is consistent with a hydraulic elevation device never reported before. The current authors hypothesize that the ancient architects could have raised the stones from inside the pyramid, in a volcano fashion. The granite stone boxes at the bottom of the north and south shafts above the Step Pyramid, previously considered as two Djoser’s graves, have the technical signature of an inlet/outlet system for water flow ( Fig 15 ). A simple modeling of the mechanical system was developed to study its water consumption and loading capacity. Considering the estimated water resources of the Wadi Taflah catchment area during the Old Kingdom, the results indicate orders of magnitude consistent with the construction needs for the Step Pyramid.

Graphical conclusion

North Saqqara map showing the relation between the Abusir water course and the Step Pyramid construction process (Inset). The arrows figuring the flow directions are approximate and given for illustrative purposes based on the Franco-Egyptian SFS/IGN survey [ 52 ]. Satellite image: Airbus Pléiades, 2021-07-02, reprinted from Airbus D&S SAS library under a CC BY license, with permission from Michael Chemouny, original copyright 2021.

https://doi.org/10.1371/journal.pone.0306690.g015

Supporting information

https://doi.org/10.1371/journal.pone.0306690.s001

https://doi.org/10.1371/journal.pone.0306690.s002

https://doi.org/10.1371/journal.pone.0306690.s003

How to cite ChatGPT

Use discount code STYLEBLOG15 for 15% off APA Style print products with free shipping in the United States.

We, the APA Style team, are not robots. We can all pass a CAPTCHA test , and we know our roles in a Turing test . And, like so many nonrobot human beings this year, we’ve spent a fair amount of time reading, learning, and thinking about issues related to large language models, artificial intelligence (AI), AI-generated text, and specifically ChatGPT . We’ve also been gathering opinions and feedback about the use and citation of ChatGPT. Thank you to everyone who has contributed and shared ideas, opinions, research, and feedback.

In this post, I discuss situations where students and researchers use ChatGPT to create text and to facilitate their research, not to write the full text of their paper or manuscript. We know instructors have differing opinions about how or even whether students should use ChatGPT, and we’ll be continuing to collect feedback about instructor and student questions. As always, defer to instructor guidelines when writing student papers. For more about guidelines and policies about student and author use of ChatGPT, see the last section of this post.

Quoting or reproducing the text created by ChatGPT in your paper

If you’ve used ChatGPT or other AI tools in your research, describe how you used the tool in your Method section or in a comparable section of your paper. For literature reviews or other types of essays or response or reaction papers, you might describe how you used the tool in your introduction. In your text, provide the prompt you used and then any portion of the relevant text that was generated in response.

Unfortunately, the results of a ChatGPT “chat” are not retrievable by other readers, and although nonretrievable data or quotations in APA Style papers are usually cited as personal communications , with ChatGPT-generated text there is no person communicating. Quoting ChatGPT’s text from a chat session is therefore more like sharing an algorithm’s output; thus, credit the author of the algorithm with a reference list entry and the corresponding in-text citation.

When prompted with “Is the left brain right brain divide real or a metaphor?” the ChatGPT-generated text indicated that although the two brain hemispheres are somewhat specialized, “the notation that people can be characterized as ‘left-brained’ or ‘right-brained’ is considered to be an oversimplification and a popular myth” (OpenAI, 2023).

OpenAI. (2023). ChatGPT (Mar 14 version) [Large language model]. https://chat.openai.com/chat

You may also put the full text of long responses from ChatGPT in an appendix of your paper or in online supplemental materials, so readers have access to the exact text that was generated. It is particularly important to document the exact text created because ChatGPT will generate a unique response in each chat session, even if given the same prompt. If you create appendices or supplemental materials, remember that each should be called out at least once in the body of your APA Style paper.

When given a follow-up prompt of “What is a more accurate representation?” the ChatGPT-generated text indicated that “different brain regions work together to support various cognitive processes” and “the functional specialization of different regions can change in response to experience and environmental factors” (OpenAI, 2023; see Appendix A for the full transcript).

Creating a reference to ChatGPT or other AI models and software

The in-text citations and references above are adapted from the reference template for software in Section 10.10 of the Publication Manual (American Psychological Association, 2020, Chapter 10). Although here we focus on ChatGPT, because these guidelines are based on the software template, they can be adapted to note the use of other large language models (e.g., Bard), algorithms, and similar software.

The reference and in-text citations for ChatGPT are formatted as follows:

• Parenthetical citation: (OpenAI, 2023)
• Narrative citation: OpenAI (2023)

Let’s break that reference down and look at the four elements (author, date, title, and source):

Author: The author of the model is OpenAI.

Date: The date is the year of the version you used. Following the template in Section 10.10, you need to include only the year, not the exact date. The version number provides the specific date information a reader might need.

Title: The name of the model is “ChatGPT,” so that serves as the title and is italicized in your reference, as shown in the template. Although OpenAI labels unique iterations (i.e., ChatGPT-3, ChatGPT-4), they are using “ChatGPT” as the general name of the model, with updates identified with version numbers.

The version number is included after the title in parentheses. The format for the version number in ChatGPT references includes the date because that is how OpenAI is labeling the versions. Different large language models or software might use different version numbering; use the version number in the format the author or publisher provides, which may be a numbering system (e.g., Version 2.0) or other methods.

Bracketed text is used in references for additional descriptions when they are needed to help a reader understand what’s being cited. References for a number of common sources, such as journal articles and books, do not include bracketed descriptions, but things outside of the typical peer-reviewed system often do. In the case of a reference for ChatGPT, provide the descriptor “Large language model” in square brackets. OpenAI describes ChatGPT-4 as a “large multimodal model,” so that description may be provided instead if you are using ChatGPT-4. Later versions and software or models from other companies may need different descriptions, based on how the publishers describe the model. The goal of the bracketed text is to briefly describe the kind of model to your reader.

Source: When the publisher name and the author name are the same, do not repeat the publisher name in the source element of the reference, and move directly to the URL. This is the case for ChatGPT. The URL for ChatGPT is https://chat.openai.com/chat . For other models or products for which you may create a reference, use the URL that links as directly as possible to the source (i.e., the page where you can access the model, not the publisher’s homepage).

Other questions about citing ChatGPT

You may have noticed the confidence with which ChatGPT described the ideas of brain lateralization and how the brain operates, without citing any sources. I asked for a list of sources to support those claims and ChatGPT provided five references—four of which I was able to find online. The fifth does not seem to be a real article; the digital object identifier given for that reference belongs to a different article, and I was not able to find any article with the authors, date, title, and source details that ChatGPT provided. Authors using ChatGPT or similar AI tools for research should consider making this scrutiny of the primary sources a standard process. If the sources are real, accurate, and relevant, it may be better to read those original sources to learn from that research and paraphrase or quote from those articles, as applicable, than to use the model’s interpretation of them.

We’ve also received a number of other questions about ChatGPT. Should students be allowed to use it? What guidelines should instructors create for students using AI? Does using AI-generated text constitute plagiarism? Should authors who use ChatGPT credit ChatGPT or OpenAI in their byline? What are the copyright implications ?

On these questions, researchers, editors, instructors, and others are actively debating and creating parameters and guidelines. Many of you have sent us feedback, and we encourage you to continue to do so in the comments below. We will also study the policies and procedures being established by instructors, publishers, and academic institutions, with a goal of creating guidelines that reflect the many real-world applications of AI-generated text.

For questions about manuscript byline credit, plagiarism, and related ChatGPT and AI topics, the APA Style team is seeking the recommendations of APA Journals editors. APA Style guidelines based on those recommendations will be posted on this blog and on the APA Style site later this year.

Update: APA Journals has published policies on the use of generative AI in scholarly materials .

We, the APA Style team humans, appreciate your patience as we navigate these unique challenges and new ways of thinking about how authors, researchers, and students learn, write, and work with new technologies.

American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000

Related and recent

Comments are disabled due to your privacy settings. To re-enable, please adjust your cookie preferences.

APA Style Monthly

Subscribe to the APA Style Monthly newsletter to get tips, updates, and resources delivered directly to your inbox.

Welcome! Thank you for subscribing.

APA Style Guidelines

Browse APA Style writing guidelines by category

• Abbreviations
• Bias-Free Language
• Capitalization
• In-Text Citations
• Italics and Quotation Marks
• Paper Format
• Punctuation
• Research and Publication
• Spelling and Hyphenation
• Tables and Figures

Full index of topics