Groundwater Flow Modeling: A Case Study of the Lower Rusizi Alluvial Plain Aquifer, North-Western Burundi

Round 1

Reviewer 1 Report

The aim of the paper entitled Groundwater flow modeling: a case study of the Lower Rusizi alluvial plain aquifer, North-western Burundi was to present the results of the of the model performance and to determine the most productive zones in groundwater in the study area. The topic of the paper is quite interesting but but the novelty of the topic is small. The abstract needs to be completely remodeled. There is no description of the goal, more important results, summary of the work. The introduction needs improvement. The introduction text is quite short and begins with a description of the research area. There is no description of similar studies or a general introduction to the subject of the article. There is no emphasis on the novelty of the work. Please add a table summarizing the assumptions made to the model. The results are fairly well described, but the discussion section should also include summary elements, or please add a summary section.

Author Response

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Reviewer 2 Report

General Comments:

This study conducted a 2D horizontal groundwater flow modelling under steady state conditions for an alluvial plain in North-western Burundi. The methods and results are fairly sound and can attract the reader's attention. However, a few minor points need to be addressed.

 

Comments and Suggestions:

• Line 22: The authors noted that the calibrated model made it possible to assess the spatial distribution of the hydraulic conductivity values at the regional scale. I think the spatial distribution of the transmissivity (= hydraulic conductivity times aquifer thickness) values is more important than the hydraulic conductivity for practical use. The assessment of the transmissivity values could support the sentence in line 27: “the developed model can be used in the planning of pumping test programs, locating areas with high groundwater potential”. This is because the transmissivity is one of the main factors in pumping tests and groundwater withdrawals. Therefore, it would be valuable to present the spatial distribution of transmissivity values in the results.
• Line 47 to 49: The sentence of “The developed model will be a predictive tool and will contribute to the resolution of problems related to the use and integrated management of the groundwater resources” is not appropriate in the introduction section. The sentence is recommended to move to the conclusion section. Also, the conclusion section is missing from the current manuscript. Conclusions should be included before publication.
• Cauchy BCs describing river-aquifer interactions at the Ntahangwa and Nyamitanga rivers were imposed the relevant river conductance values were calibrated for modelling in the study. However, the calibrated river conductance values could not be found in the manuscript. The river stage values assigned to model are not shown. Did authors use the River package or the Stream package in the MODFLOW software ?
• Line 311 to 314: The differences between computed and observed piezometric heads for 115 wells were noted. It is desirable to calculate statistical measures.
• Check the unit of conductance in Table 4.

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Author Response

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Reviewer 3 Report

1.      The aquifer should be listed or presented with some profiles to let the reader understand the distribution condition. For example, Fig. 4 shows the lower plain, but we can not determine the depth and range. Maybe a contour of the lower plain elevation map can help.

2.      Fig. 5 shows a piezometric reference map of lower pain, but there is a strange ‘S’ shape at the left between 790 to 785 without productive wells. The map is quite different from the computed map in Figure 10.

3.      The estimated recharge is cut with a line, why?

4.      The lines in Figure 10 and Figure 11 are rivers and will confuse the readers’ judgment. For example, the flux vectors are not toward the rivers.

Author Response

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Round 2

Reviewer 1 Report

The paper has been improved in accordance with remarks from review and could be published.