Reconstructing Groundwater Storage Changes in the North China Plain Using a Numerical Model and GRACE Data
Round 1
Reviewer 1 Report
This paper presents and discusses the results of a numerical model with improved free data by solving several issues in data collecting such as low resolution; lack in gap periods; and expensive information. The model presented is the result of different integration modeling techniques such as the NGFLOW-GRACE to construct a refined model to explore groundwater storage changes, which is applied to the most populated region in China.
The study is complex and provides more options for groundwater studies in regions with data issues like those mentioned previously. The methods, results a discussion are very explicit, although there may be more explanations for the comparative results in the models, the authors provide the most suitable explanation for their results. Finally, the authors are self-critical of their research, pointing out the main weaknesses of their models and in general of their study.
I have the next minor comments:
The paper counts with many acronyms most of them with definitions, however, there are some for which I didn’t find the meaning o it is not previously defined they are: SCE-UA (in the abstract); GRACE-GLDAS (line 427); GCDI (line 858)
In the introduction, the statement about the global consumption of groundwater is a little confusing, since at the beginning 50% is declared and then 35 %. Just be clearer.
There is a mistake in line 60 with the cite, only 10 must be indicated, not 1010.
Please explain more on how a lake can be measured in linear km.
In general, consider increasing the size of figures, in particular, figure 1’s explanation the Acronyms are not defined (NH, SO, HR, etc)
What does “manual” mean in line 228?
The definition of Qnc is missing from equation 2.
Terrestrial means surface in line 368?
Are the wells of Table 4 positioned on some map?
Author Response
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Author Response.docx
Reviewer 2 Report
This manuscript employs a model (NGFLOW-GRACE) based on conventional groundwater mathematical models, deriving a mathematical expression for changes in groundwater storage based on Darcy's Law and the principle of water balance. The research area was divided into different grids, each with its own Dirichlet boundary. Subsequently, the calibrated groundwater storage model was used to simulate changes in groundwater storage during the gap period. The performance of the model was evaluated using Root Mean Square Error (RMSE), measuring the overall consistency between the observed values and the computed GWSA values.
This study provides a high-resolution set of North China groundwater products, demonstrating a certain level of innovation and furthering research on the factors influencing groundwater in the North China Plain. However, there are still some incomplete and unclear reasons in the current manuscript. On the whole this paper should be modified for minor revision before final approval. The authors should address the comments as follows.
1. This study identifies the hydraulic gradient coefficient as exhibiting the highest sensitivity. It is recommended to delve deeper into the reasons for this phenomenon and analyze it in the discussion section.
2. The method used to fill in data for the gap period should be clarified in the revision.
3. The subscripts in the formulas are overly lengthy, which affects aesthetics.
4. The correlation used to evaluate the results is reliable, but have other evaluation metrics been used to explain the reliability of the results from different perspectives? It is suggested to add interpretations from other third-party viewpoints.
5. A brief explanation for the differing trends in the Mo and Li data should be provided in the revision, along with the reasons for choosing to use the Li data.
6. The study area of the paper is the North China region. Should the discussion consider the impact of the South-to-North Water Diversion project and groundwater recovery? It is suggested to understand the research area in combination with data from more dimensions.
The authors should carefully address the language writing issue to make the manuscript more understandable.
Author Response
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Reviewer 3 Report
General comments:
Reviewer highly appreciates the authors for this work. The topic of article is good and adds to the new trend in the using of model and GRACE data for reconstructing groundwater storage changes
However, there are some comments as follows:
1. The introduction section is very long.
2. In the study area section lines 212 – 224, a complete hydrogeological data for the studied Quaternary aquifer are required as well as hydrogeological cross sections. In addition to the hydraulic parameters of this aquifer must be added which are very important in groundwater storage description and movement within the aquifer (pumping tests analysis).
3. In the determination of groundwater storage, it is very important to show the groundwater movement (water table map) and direction of flow as well as the recharge sources of the studied aquifer (please add).
4. Results and discussions are very good and give the reader a clear view about the reconstructing groundwater storage changes in the study area.
5. All figure are good and clear.
6. Conclusion section should be contains recommendations for this study.
Author Response
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Round 2
Reviewer 3 Report
The manuscript had been improved
