A Systematic Review of the Current State of Numerical Groundwater Modeling in American Countries: Challenges and Future Research
, Diego Armando MartÃnez Cruz 3, José Alfredo Ramos Leal 1, Eliseo Hernández Pérez 1, Joel GarcÃa Pazos 4 and Oscar Guadalupe Almanza Tovar 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsReview the manuscript entitled “A systematic review of the current state of numerical groundwater modeling in Latin American countries: Challenges and Future research.”
This study collected 166 journal articles and analyzed their discussion issues and numerical model simulations to understand the contribution to groundwater management. Overall, the topic is interesting and the analyses results illustrate the main study issues in the field of groundwater modeling. It can be considered for publication after medium revision. Below are some comments and suggestions for your reference:
General comments
1. For an international journal article, novelty is a key factor for a manuscript being accepted, especially for a top journal. Therefore, an article based on application or case study is not easy published in this kind of journal. For example, applying a numerical tool to develop a groundwater flow model and assess the groundwater resource, contamination, seawater intrusion, land subsidence, etc., even including scenario simulation, future prediction, and climate change, this kind of results do not include sufficient novelty and thus is difficult to be accepted for publication in a top journal. From some of the selected journals in this study, it looks like the target articles does not totally match the motivation, although the analyzed results still match the general concept. Articles addressed application or case study might be more commonly seen in medium to low level journals. It is suggested that clarifying the motivation and selecting suitable journals should be the priority of this study.
2. It is unclear that why this study only focuses on some specific issues. For example, Latin American countries, publish year, language, title, simple model, etc. The criteria for the selection can be described more clear to avoid confusion.
3. English writing can be improved before it is published. I found a lot of mistakes in English writing, though I do not list them below.
Specific comments
1. Lines 122-124. The meaning of these two sentences are the same.
2. Lines 140-141. Some articles will address the novelty and avoid a case study, therefore they will not include “case study” in the title. However, the content o these articles might still match the requirement of this study.
3. Table 1. “groundwater” is a professional term used in groundwater hydrology. However, there still some researchers use “ground water”, “underground water”, or “subsurface water.” Some terms relate to groundwater could also be tried to collect as more as articles.
4. Lines 225-228. It is suggested to provide the reason to exclude the integrated hydrological model. Some integrated models are also suitable for the discussed issues.
5. Line 246. What does the size (one, two, or three size) means?
6. Line 256. The description of “These codes simulate flow and transport in a coupled manner” might not be correct. Coupled model means interactions between variables. At least some of the models are not coupled models.
7. Lines 308-310. The descriptions are confusing. It does not include basin and thus the total amount of the percentage is not 100%. It might be more clear to state that these descriptions exclude basin.
8. Lines 434-435. Although climate change is an important issue, most of the hydrologists do not consider it in the simulation. Because climate change assessment needs to include the climate change scenarios, which are based on plenty of assumptions, and it is commonly in a very large scale. Not all areas have a suitable scale for climate change assessment and not all researchers agree with the General Circulation Models (GCMs). For me, I did some researches on climate change impacts on groundwater resources. But I do not think that climate change is an important condition that hydrologists should consider it in simulation. It depends on the purpose of the simulations.
Comments on the Quality of English LanguageEnglish writing can be improved before it is published. I found a lot of mistakes in English writing, though I do not list them in comments.
Author Response
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REVIEWER 1 |
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Comments and Suggestions The changes requested are colored yellow |
Answers The changes made are colored green |
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General comments |
Thank you so much for your comment. We appreciate your suggestion. We have improved the introduction and we have clarified the motivation of the study. We have added suitable journals in this section. So, we addressed the writing errors to avoid an affectation in the reading experience.
In most regions, groundwater scarcity could limit economic and social development [1–3]. Groundwater resources provide more than one-third of drinking water world-wide and around 43% for irrigation [3–5]. In irrigated regions, the extraction rates are highest, and so are the principal sources of groundwater depletion [6,7]. Currently, groundwater resources account for about 33 % of global water withdrawals, which is estimated to increase by 39% by 2050 [8]. Hence, water resources are increasingly threatened by over-extractions. More difficult challenges are predicted at regional and local scales in many countries worldwide [8].
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In addition, the American region presents large transboundary aquifers that challenge water resource management due to diverse interests in use and preservation [11,12].
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Climate change affects water availability through its influence on precipitation, air temperature, evapotranspiration, vegetation cover, and other climate variables that impact groundwater resources [5,14].
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Therefore, to meet the challenges of sustainable management of water resources, it is vital to know the current status and the forecasting of future groundwater conditions [16]. Page 2 (Lines:58-60) This study provides a comprehensive systematic review of the current knowledge on the use of numerical groundwater flow models applied for planning and water re-sources management in American countries such as the United States, Mexico, Cana-da, Brazil, Argentina, Chile, Colombia, Cuba, Uruguay, Nicaragua, Guatemala, and Haiti. To the extent of our understanding, this is the first study reviewing the numerical simulation models applied to water resources management in the American region. This review aims to fill this gap. Since then, researchers have reported that sustainable water resource management in the American region has been little studied [11].
The relevance of this study is based on the need-to-know state-of-the-art on the application of numerical groundwater models. This study aims to compile up-to-date of 166 papers since the first efforts were carried (2000) out until February 2024, which were analyzed, classified, and compared. These research articles were examined considering applied software, studied regions, performance metrics, modeling units, and types of aquifers (confined, semi-confined, unconfined, karstic), etc.
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1. For an international journal article, novelty is a key factor for a manuscript being accepted, especially for a top journal. Therefore, an article based on application or case study is not easy published in this kind of journal. For example, applying a numerical tool to develop a groundwater flow model and assess the groundwater resource, contamination, seawater intrusion, land subsidence, etc., even including scenario simulation, future prediction, and climate change, this kind of results do not include sufficient novelty and thus is difficult to be accepted for publication in a top journal. From some of the selected journals in this study, it looks like the target articles does not totally match the motivation, although the analyzed results still match the general concept. Articles addressed application or case study might be more commonly seen in medium to low level journals. It is suggested that clarifying the motivation and selecting suitable journals should be the priority of this study. |
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2. It is unclear that why this study only focuses on some specific issues. For example, Latin American countries, publish year, language, title, simple model, etc. The criteria for the selection can be described more clear to avoid confusion. |
Thank you so much for your comment. We have rewritten the paragraph and we addressed the writing errors.
Four sequential filters were applied as inclusion and exclusion criteria. We considered the year of publication since the first efforts were carried out (2000) until February 2024. Related to document type, we have considered only research articles. Related to language, we considered research articles written in English and Spanish since they are universal and native languages, respectively. The fourth criterion is the region. We considered American countries such as the United States, Mexico, Canada, Brazil, Ar-gentina, Chile, Colombia, Cuba, Uruguay, Nicaragua, Guatemala, and Haiti), taking advantage of the automatic tools available in the databases. The countries of America mentioned above were the only ones in which studies related to the objective of this systematic review were identified.
Pages 4 and 5 (Lines: 118-127)
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3. English writing can be improved before it is published. I found a lot of mistakes in English writing, though I do not list them below. |
Thank you so much for your observation and comment. We addressed the writing errors in the whole manuscript including the English to avoid an affectation in the reading experience.
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Specific comments |
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1. Lines 122-124. The meaning of these two sentences are the same.
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Thank you very much for your suggestion. We removed duplicate sentence.
The methodology developed in this systematic review is displayed in the flowchart shown in Figure 1 [25].
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2. Lines 140-141. Some articles will address the novelty and avoid a case study, therefore they will not include “case study” in the title. However, the content o these articles might still match the requirement of this study.
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Thank you very much for your comment. Due to the objective of this study was evaluate the current knowledge on the use of numerical groundwater flow models applied for planning and water resources management. We focus on the application of software to case studies such as basin, aquifer and river-aquifer interaction.
This study provides a comprehensive systematic review of the current knowledge on the use of numerical groundwater flow models applied for planning and water re-sources management in American countries…. Page 2 (Lines: 76-78)
The relevance of this study is based on the need-to-know state-of-the-art on the application of numerical groundwater models… Page 2 (Lines: 85-86) |
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3. Table 1. “groundwater” is a professional term used in groundwater hydrology. However, there still some researchers use “ground water”, “underground water”, or “subsurface water.” Some terms relate to groundwater could also be tried to collect as more as articles.
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Thank you very much for your suggestion. We have added the keywords it suggests to the database search algorithm, but the collection of articles was the same.
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4. Lines 225-228. It is suggested to provide the reason to exclude the integrated hydrological model. Some integrated models are also suitable for the discussed issues.
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Thank you very much for your suggestion. We have described the reason why integrated hydrological models were excluded from the research.
The software and codes selected were exclusively focused on groundwater modeling, excluding integrated hydrological process software. ParFlow [41], HydroGeoSphere [42], MikeSHE [43], CATHY [44], and SWAT [45] are examples of integrated models that are widely reported in the scientific literature. Integrated models represent the en-tire land water cycle, incorporating key processes such as evapotranspiration, snow accumulation and melting, runoff, water routing at the surface and in the river chan-nel, infiltration, groundwater flow, and groundwater discharge to surface reservoirs [46].
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5. Line 246. What does the size (one, two, or three size) means?
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Thank you very much for your observation. We refer to the geometry of the model (1D, 2D, and 3D dimensions)
“…model geometry (1D, 2D, and 3D dimensions)…”
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6. Line 256. The description of “These codes simulate flow and transport in a coupled manner” might not be correct. Coupled model means interactions between variables. At least some of the models are not coupled models.
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Thank you so much for your comment. We rewrite the sentence in the text. We have changed the word “coupled” to a more appropriate word.
These codes are used in conjunction with groundwater flow models. Examples of widely reported numerical codes in the scientific literature include MODPATH [67], and MT3DMS [68], among many others reviewed by Machiwal et al. [69].
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7. Lines 308-310. The descriptions are confusing. It does not include basin and thus the total amount of the percentage is not 100%. It might be more clear to state that these descriptions exclude basin.
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Thank you very much for your observation. We have rewritten the sentence and modified figure 7, for a better understanding of the text.
Most studies focused on modeling the aquifer as the target unit (Figure 7A). The type of aquifer conceptualized in the studies are unconfined aquifer (53%), confined aquifer (16%), semi-confined aquifer (14%), coastal aquifer (11%), and karst aquifer (6%) (Figure 7B).
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8. Lines 434-435. Although climate change is an important issue, most of the hydrologists do not consider it in the simulation. Because climate change assessment needs to include the climate change scenarios, which are based on plenty of assumptions, and it is commonly in a very large scale. Not all areas have a suitable scale for climate change assessment and not all researchers agree with the General Circulation Models (GCMs). For me, I did some researches on climate change impacts on groundwater resources. But I do not think that climate change is an important condition that hydrologists should consider it in simulation. It depends on the purpose of the simulations. |
Thank you so much for your comment. We have described some of the reasons why we consider it fundamental to begin to evaluate the impacts of climate change on groundwater using numerical models of groundwater flow.
This omission could be reducing the effectiveness of the studies. Previous studies have reported significant effects on groundwater resources attributed to climate change [98]. Researchers have described significant impacts of the climate change on water resources including variability in precipitation and groundwater recharge, changes in water demand, sea level rise, altered evapotranspiration, etc. [6,93,118]. Without ac-counting for climate change, models may result in underestimating or misinterpreting future risks associated with groundwater availability [98]. Therefore, future studies should consider the effects of climate change on groundwater management and per-form long-term transient state simulations to assess the impact of temporal variability and aquifer storage potential [21]. Predicts based on climatic trends are vital for accu-rate modeling and effective water resources management.
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors presented a detailed overview of the current state of numerical groundwater modeling in Latin American countries, thus making an important contribution to the scope of research on the topic. In this way, the topicality and necessity of numerical modeling of groundwater was demonstrated, and it is expected that this type of research will intensify in the future. In fact, numerical modeling is becoming one of the most important methods for researching the quality and quantity of groundwater for scientific purposes, and numerical models are also essential to ensure accuracy and timeliness in groundwater management. I believe that the paper is well designed, the methods are adequately described and the results are appropriately presented. For this reason, I consider the work suitable for publication in the scientific journal. At this stage, I have only two minor comments, which I outline below:
1. Lines 123-124: Figure 1 displays the flowchart of the methodology developed in this systematic review.' I suggest deleting the sentence, since the same content is already given in the sentence before it.
2. Line 199: Correct the longitude marking in Figure 4 with an abbreviation from English - West (W).
Author Response
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REVIEWER 2 |
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Comments and Suggestions The changes requested are colored yellow |
Answers The changes made are colored green |
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1. Lines 123-124: Figure 1 displays the flowchart of the methodology developed in this systematic review.' I suggest deleting the sentence, since the same content is already given in the sentence before it.
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Thank you very much for your suggestion. We removed duplicate sentence.
The methodology developed in this systematic review is displayed in the flowchart shown in Figure 1 [25].
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2. Line 199: Correct the longitude marking in Figure 4 with an abbreviation from English - West (W).
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Thank you very much for your observation. We changed the longitude marking in the figure 4 with "W".
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for Authors
The article is interesting, it presents a very comprehensive review of the current state of numerical groundwater modeling on an international scale; a wide range of different aspects are taken into account
GENERAL NOTE
Canada and the United States are not considered Latin American countries. Either the title should be corrected, leaving the phrase "...American countries", or leaving the existing title, the content of the article requires a change by effectively limiting it to Latin American countries.
According to BRITTANICA (https://www.britannica.com/topic/list-of-countries-in-Latin-America-2061416): Latin America is generally understood to consist of the entire continent of South America in addition to Mexico, Central America, and the islands of the Caribbean whose inhabitants speak a Romance language. The peoples of this large area shared the experience of conquest and colonization by the Spaniards and Portuguese from the late 15th through the 18th century as well as movements of independence from Spain and Portugal in the early 19th century.
This is an alphabetically ordered list of countries in Latin America:
(North and Central America): Belize, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama
(South America): Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Peru, Suriname, Uruguay, Venezuela,
(Caribbean countries): Cuba, Dominican Republic, Haiti
(dependencies and constituent entities): Guadeloupe, Martinique, Puerto Rico, Saint-Barthélemy, Saint-Martin
DETAILED NOTES
Some key words unnecessarily duplicate expressions contained in the title of the article (groundwater, Latin America, numerical modeling). Keywords are used to improve the search for interesting articles in publication databases and should not duplicate the content of the title, but complement and/or expand it.
Line 103, 133 - which countries? Maybe it's worth presenting the specific countries taken into account? Or refer additionally to figure 4?
Figure 5 in the form presented is difficult to read (too low drawing resolution and/or too high compression); a larger drawing would be preferable
Line 232: in FDM, the Modflow simulator is used to calculate only groundwater flow equations (without "transport conditions"); additional codes are used to simulate mass transport: MT3D, MT3DMS, RT3D, etc.
Line 236-238 - no mention of Processing Modflow (PMWIN). Is it not used?
Line 242: FD and FE (not “EF”)
Line 253 mentions PMWIN in the context of solute transport, while it is most often used for groundwater flow modeling. Moreover, PMWIN (Processing Modflow) is not a numerical code (line 252); it's a software platform to groundwater modeling (like Visual Modflow, GMS)
Table 2 - unnecessary combination of codes and software in one list. I suggest separating them into codes/simulators (e.g. Modflow, MT3D, MT3DMS, etc.) and software separately (e.g. ModelMuse, Visual Modflow, GMS, Processing Modflow, etc.). It may be helpful to refer to information contained on the websites of manufacturers of individual software or a synthetic summary of the capabilities of individual programs available in published form (such as a review of applications for groundwater modeling)
Table 2 - PMWIN is Processing Modflow, also referred to as PM. PMWIN as a program name is currently rarely used; the name Processing Modflow is in use.
Figure 6: the Frequency axis means the number of occurrences or their percentage share?
Line 288 - according to Fig. 6A, the performance of hydrological models using two or more metrics is greater than one metrics; therefore it cannot be 42%; either an error in the data or an incorrectly constructed graph in Fig. 6A.
Line 288-289 - "hydrologic" or "hydrogeological" models?
Line 451 “Latin America”? or “America”?
Author Response
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REVIEWER 3 |
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Comments and Suggestions The changes requested are colored yellow |
Answers The changes made are colored green |
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GENERAL NOTE |
Thank you very much for your observation. We appreciate your suggestion. We have corrected the title, leaving the phrase “….American countries…”. Also, we have changed the phrase “Latin American countries” by “American countries” in all manuscript.
A systematic review of the current state of numerical ground-water modeling in American countries: Challenges and Future research
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Canada and the United States are not considered Latin American countries. Either the title should be corrected, leaving the phrase "...American countries", or leaving the existing title, the content of the article requires a change by effectively limiting it to Latin American countries. |
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DETAILED NOTES |
Thank you very much for your observation. We removed duplicate keywords in the title and added other keywords.
Keywords: FEFLOW, Flow simulation, Forecasting, Hydrogeological model, Performance metrics, MODFLOW, Water resources management
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Some key words unnecessarily duplicate expressions contained in the title of the article (groundwater, Latin America, numerical modeling). Keywords are used to improve the search for interesting articles in publication databases and should not duplicate the content of the title, but complement and/or expand it.
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Line 103, 133 - which countries? Maybe it's worth presenting the specific countries taken into account? Or refer additionally to figure 4?
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Thank you very much for your suggestion. We have added specific research countries.
…..American countries such as the United States, Mexico, Canada, Brazil, Argentina, Chile, Colombia, Cuba, Uruguay, Nicaragua, Guatemala, and Haiti….
Page 2 (Lines: 78-79) ….We considered American countries such as the United States, Mexico, Canada, Brazil, Argentina, Chile, Colombia, Cuba, Uruguay, Nicaragua, Guatemala, and Haiti), taking advantage of the automatic tools available in the databases….
Pag 4 (Lines:123-127)
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Figure 5 in the form presented is difficult to read (too low drawing resolution and/or too high compression); a larger drawing would be preferable.
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Thank you very much for your observation. We have increased and size of the figure 5.
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Line 232: in FDM, the Modflow simulator is used to calculate only groundwater flow equations (without "transport conditions"); additional codes are used to simulate mass transport: MT3D, MT3DMS, RT3D, etc. Line 236-238 - no mention of Processing Modflow (PMWIN). Is it not used?
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Thank you so much for your comment. We have included Processing Modflow along with the other software (Visual Modflow, Model Muse). Of the software, PMWIN is the least used.
The most commonly used software in this field of research is Visual MODFLOW [60], followed by MODELMUSE [61], GROUNDWATER Vistas (GV; [62]), Groundwa-ter Modeling System (GMS; [63,64]), and Processing Modflow for WINdows (PMWIN; [65]). Of these, PMWIN is the least utilized.
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Line 242: FD and FE (not “EF”)
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Thank you very much for your observation. We changed “EF” by “FE”
….. These software types (FD and FE) are widely used for numerical modeling….
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Line 253 mentions PMWIN in the context of solute transport, while it is most often used for groundwater flow modeling. Moreover, PMWIN (Processing Modflow) is not a numerical code (line 252); it's a software platform to groundwater modeling (like Visual Modflow, GMS)
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Thank you so much for your comment. We have included Processing Modflow along with the other software for groundwater flow modeling (Visual Modflow, Model Muse).
These codes are used in conjunction with groundwater flow models. Examples of widely reported numerical codes in the scientific literature include MODPATH [67], and MT3DMS [68], among many others reviewed by Machiwal et al. [69]. The
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Table 2 - unnecessary combination of codes and software in one list. I suggest separating them into codes/simulators (e.g. Modflow, MT3D, MT3DMS, etc.) and software separately (e.g. ModelMuse, Visual Modflow, GMS, Processing Modflow, etc.). It may be helpful to refer to information contained on the websites of manufacturers of individual software or a synthetic summary of the capabilities of individual programs available in published form (such as a review of applications for groundwater modeling)
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Thank you very much for your suggestion. We have separated the codes from the software. A description of the software and codes is shown in the cited articles.
Table 2. Numerical groundwater codes/softwares [17,18,76,77].
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[17]. Kumar, C. P.; Singh, S. Concepts and Modeling of Groundwater System. International Journal of Innovative Science, Engineering & Technology 2015, 2 (2), 262–271.
[18]. Kumar, C. P. An Overview of Commonly Used Groundwater Modelling Software. International Journal of AdvancedResearch in Science, Engineering and Technology 2019, 6 (1), 7854–7865.
[76]. Yang, X.; Steward, D. R.; De Lange, W. J.; Lauwo, S. Y.; Chubb, R. M.; Bernard, E. A. Data Model for System Conceptualization in Groundwater Studies. International Journal of Geographical Information Science 2010, 24 (5), 677–694. https://doi.org/10.1080/13658810902967389.
[77]. Kumar, C. P. GROUNDWATER FLOW MODELS. International Journal of Modern Sciences and Engineering Technology 2015, 2 (2), 18–27. |
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Table 2 - PMWIN is Processing Modflow, also referred to as PM. PMWIN as a program name is currently rarely used; the name Processing Modflow is in use.
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Thank you so much for your comment. We correct the name of PMWIN to Processing Modflow for WINdows.
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Figure 6: the Frequency axis means the number of occurrences or their percentage share?
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Thank you very much for your observation. In the Figure 6A the frequency corresponds to the number of occurrences. We have clarified this observation in the text.
…Figure 6A shows the number of PM's used to evaluate a model vs. frequency (number of occurrences)...
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Line 288 - according to Fig. 6A, the performance of hydrological models using two or more metrics is greater than one metrics; therefore it cannot be 42%; either an error in the data or an incorrectly constructed graph in Fig. 6A.
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Thank you very much for your observation. The data and graphics are correct. We have rewritten the sentence in the text.
…43% of the studies evaluated the performance of hydrogeological models using two or more metrics, while 37% used a single metric and the remaining 20% did not mention any performance metric...
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Line 288-289 - "hydrologic" or "hydrogeological" models?
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Thank you very much for your observation. We changed "hydrologic" by "hydrogeological".
…43% of the studies evaluated the performance of hydrogeological models using two or more metrics… Page 11 (Line 288)
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Line 451 “Latin America”? or “America”?
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Thank you very much for your observation. We changed "Latin America" by "America" as in the whole document.
…..groundwater flow models used to evaluate water resources management in America from 2000 to 2024...
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsMost of the suggestions and comments have been considered in the revised manuscript. Only the reply about climate change should be considered in the groundwater modeling I cannot totally accept. As I mentioned in the last comments that not all the researchers agree the scenarios of climate change data generated by the plenty of assumptions. Even thought, I respect authors' opinion and statement.
Comments on the Quality of English LanguageMost of the mistakes have been corrected. Only a few sentences need further proofreading.
