Investigating Climate Change Effects on Evapotranspiration and Groundwater Recharge of the Nile Delta Aquifer, Egypt
, Ismail Abd-Elaty 3, Ahmed Elbeltagi 4, Martina Zeleňáková 5,* and Ismail Fathy 3Round 1
Reviewer 1 Report
The authors studied and discussed the climate change effect on evapotranspiration and groundwater recharge of the Nile Delta Aquifer in Egypt. This is an interesting issue for sustainable groundwater management and the authors showed us a possible results for their relationship.
A more detailed discussion on the realtionship between evaptranspiration and groundwater recharge should be considered in the revised manuscript.
The following is some suggestions for your reference.
1) There is no show of profile A-A' in Fig.1.
2) "Maize" should be "maize" in line 177, and "Wheat" should be "wheat" in line 180.
3) Line 208-209, I think the unit of "R" should be 1/d, not m^3/d. Please check and verify the correct unit.
4) Line 209, the unit of "Sss" should be "1/m" in 3D flow equation, not dimensionless. By the way, "Ss" means specific storage, not specific storage coefficient.
Author Response
We thank you and the reviewer for your time and efforts in revising the manuscript. We carefully addressed all the raised comments and suggestions by the reviewers. Kindly find enclosed our reply and the attached revised version of the manuscript.
The authors studied and discussed the climate change effect on evapotranspiration and groundwater recharge of the Nile Delta Aquifer in Egypt. This is an interesting issue for sustainable groundwater management and the authors showed us possible results for their relationship.
A more detailed discussion on the relationship between evapotranspiration and groundwater recharge should be considered in the revised manuscript.
The following are some suggestions for your reference.
Comment # 1:
There is no show of profile A-A' in Fig.1.
Authors' response:
Done, a hydrogeological cross-section from south to north was added as Fig. 1 b. See line 148.
Comment # 2:
"Maize" should be "maize" in line 177, and "Wheat" should be "wheat" in line 180.
Authors' response:
Done.
Comment # 3:
Line 208-209, I think the unit of "R" should be 1/d, not m^3/d. Please check and verify the correct unit.
Authors' response:
Yes, the unit was corrected as well as eq 1. Please see the lines between 211 and 213.
Comment # 4:
Line 209, the unit of "Sss" should be "1/m" in the 3D flow equation, not dimensionless. By the way, "Ss" means specific storage, not specific storage coefficients.
Authors' response:
Done, please see the lines between 214 and 215.
Reviewer 2 Report
As a paper for a Special Issue, I support publishing it. However, the manuscript needs a good deal of improvement and fine tuning. Here are my thoughts.
(1) The paper uses MODFLOW model to predict Evapotranspiration in the Nile Delta Aquifer in the coming decades. The authors use Maize and Wheat as the only crops in the study area. What about the other plant types, grass etc.?
(2) The calibration and validation of the model is not clear. One of the powerful techniques used in these types of studies is the use of stable oxygen and hydrogen isotopes. For example, there is a study based on Nile Delta aquifer. This is the study
Abdel MawgoudMohammed, R.V.Krishnamurthy,Alan E.Kehew, Laura J.CrosseycKarl K.Karlstrom (2016) Factors affecting the stable isotopes ratios in groundwater impacted by intense agricultural practices: A case study from the Nile Valley of Egypt. Science of The Total Environment Volume 573, 15 707-715,
The authors should discuss this approach if not in great detail
(3) In their figures, for example Figure 3, I see some cyclicity. It looks interesting and the authors need to explore this further. Why the cyclicity?
(4) Lines 252-260. The authors talk about linear regression which are well known. This can be eliminated. This is High School stuff. Also they do not talk about the r2 value or the p value. This is clear from Fig 6a. There is a cyclicity here also but they chose to plot a linear regression without any r value or significance.
(5) In the conclusions the authors say “the actual ET is correlated with the combination of solar radiation, vapor pressure deficit and humidity are the best variables to explain their model”. I am confused. They should explain how these variables actually affect the ET. They are all related to each other. I would suspect that the humidity factor is the main variable and that is perhaps linearly affected by the other variables.
(6) Since this is a theoretical prediction, it would be nice to know what the model production is if agricultural practices double due to population increase.
(7) The language can be improved. I noticed at least a couple
Line 46 is incomplete.
Lines 102-103. Evapotranspiration and soil moisture are “depending” on the …. It should be “depend on”
Line 156-157. “is ranged between” is incorrect. Just say “range between”
In sum, if the above issues are addressed, the manuscript will look a lot better.
Comments for author File: 
Comments.docx
Author Response
We thank you and the reviewers for your time and efforts in revising the manuscript. We carefully addressed all the raised comments and suggestions by the reviewers. Kindly find enclosed our reply and the attached revised version of the manuscript.
As a paper for a Special Issue, I support publishing it. However, the manuscript needs a good deal of improvement and fine-tuning. Here are my thoughts.
Comment # 1:
The paper uses the MODFLOW model to predict Evapotranspiration in the Nile Delta Aquifer in the coming decades. The authors use Maize and Wheat as the only crops in the study area. What about the other plant types, grass, etc.?
Authors' response:
Maize and wheat were selected as two major crops in the Nile Delta for the summer and winter seasons where wheat is currently cultivated at 3.6 million acres which is the largest area of wheat production in Egypt’s history and maize is the second grain crop according to FAO. This justification for selecting such crops was edited. Please see lines between 179 and 187.
Comment # 2:
The calibration and validation of the model are not clear. One of the powerful techniques used in these types of studies is the use of stable oxygen and hydrogen isotopes. For example, there is a study based on the Nile Delta aquifer. This is the study
Abdel MawgoudMohammed, R.V.Krishnamurthy, Alan E.Kehew, Laura J.CrosseycKarl K.Karlstrom (2016) Factors affecting the ratios of the stable isotopes in groundwater impacted by intense agricultural practices: A case study from the Nile Valley of Egypt. Science of The Total Environment Volume 573, 15 707-715, The authors should discuss this approach if not in great detail
Authors' response:
The model calibration section was edited as well as Fig. 5 a–d. Please see lines between 226 and 233, and line 235.
Comment # 3:
In their figures, for example, Figure 3, I see some cyclicity. It looks interesting and the authors need to explore this further. Why the cyclicity?
Authors' response:
This figure shows the average ETc (cm) in the North, middle and south Nile Delta Zones. The values of actual ETc are related to the climate variables for solar radiation, vapor pressure deficit, and humidity. So, ETc increased from year 1958 to 1964 and decreased from 1964 to 1981. Also, it increased in year 1982 and return to decrease from 1982 to 1999 while it increased in year 2000 and from years 2000 to 2007 decreased and return to increase from 2007 to 2020. This change in the increasing and decreasing may be attributed to the variation of these climate variables and climate change. This sentence was added. Please see lines between 182 and 187.
Comment # 4:
Lines 252-260. The authors talk about linear regression which is well-known. This can be eliminated. This is High School stuff. Also, they do not talk about the r2 value or the p-value. This is clear from Fig 6a. There is a cyclicity here also but they chose to plot a linear regression without any r value or significance.
Authors' response:
The authors agreed to remove the text about linear regression as it is well-known. In the related figure, authors used the historical data from 1958 to 2020 for ETc and got the results of mean, median, and mode without using other statistical models to predict the trend of ETc in years 2030, 2050, and 2070, in further research, authors will apply statistical models about the estimation of ETc and get the other statistical variables as the p-value and the correlation between the different climatic variables as well.
Comment # 5:
In the conclusions, the authors say “the actual ET is correlated with the combination of solar radiation, vapor pressure deficit and humidity are the best variables to explain their model”. I am confused. They should explain how these variables actually affect the ET. They are all related to each other. I would suspect that the humidity factor is the main variable and that is perhaps linearly affected by the other variables.
Authors' response:
The authors totally agree with you that the combination of solar radiation, vapor pressure deficit, and humidity are related to each other, so authors added the following sentence to the text “The increasing of solar radiation and vapor pressure deficit convert a considerable amount of liquid water into water vapor and water demands while increasing humidity tends to reduce transpiration”. Please see the lines between 361 and 363.
Comment # 6:
Since this is a theoretical prediction, it would be nice to know what the model production is if agricultural practices double due to population increase.
Authors' response:
In Egypt, agriculture over the years is by two or three seasons so any changes in agricultural practices by double will require large quantities of irrigation water which will lead to a considerable increase in the water shortage
Comment # 7:
The language can be improved. I noticed at least a couple:
Line 46 is incomplete.
Authors' response:
Done. See line 50.
Comment # 8:
Lines 102-103. Evapotranspiration and soil moisture are “depending” on the …. It should be “depend on”
Authors' response:
Done. Please see line 104.
Comment # 9:
Line 156-157. “is ranged between” is incorrect. Just say “range between”
Authors' response:
Done. See lines 156, 157, and 158.
Reviewer 3 Report
The paper is interesting and concerns one of the main challenges in the fight against climate change: water management.
In line 103 there is 'on principle' perhaps the term is not correct
in Figure 1b it might be useful to show the two canals Ismailia and Nubaria to understand better the boundaries of the studied area
In the description of the simulation results in the future scenarios, perhaps too many numbers are given and it is difficult to follow. Perhaps to make it quicker to read, only the % increases or decreases could be reported, perhaps reporting the numbers, show in Figure 7, in a separate table.
On page 9 there are two figures 6 the second one should be corrected with 7
The conclusions are very brief and it would be good to better explain the results and especially the impacts they may have on the management of the resource and on agriculture.
Author Response
We thank you and the reviewer for your time and efforts in revising the manuscript. We carefully addressed all the raised comments and suggestions by the reviewers. Kindly find enclosed our reply and the attached revised version of the manuscript.
The paper is interesting and concerns one of the main challenges in the fight against climate change: water management.
Comment # 1:
In line 103 there is 'on principle' perhaps the term is not correct
Authors' response:
Yes. The sentence was edited to be “Moreover, ETc and soil moisture depletion depend on climatic parameters such as temperature, relative humidity, wind speed, and sunshine hours”. Please see lines 104–105.
Comment # 2:
in Figure 1b it might be useful to show the two canals Ismailia and Nubaria to understand better the boundaries of the studied area
Authors' response:
Done. Fig 1 a was edited to show irrigation canals and drains in the Nile Delta in addition to editing Fig. 4 a to highlight the boundary condition in the model simulation. Please see lines 148 and 218.
Comment # 3:
In the description of the simulation results in future scenarios, perhaps too many numbers are given and it is difficult to follow. Perhaps to make it quicker to read, only the % increases or decreases could be reported, perhaps reporting the numbers, shown in Figure 7, in a separate table.
Authors' response:
Done, Table 3 was added to summarize the percentage of difference (increase, + or decrease, -) for each boundary parameter for 2030, 2050, and 2070 than the current situation of the aquifer (base case). Please see line 324.
Comment # 4:
On page 9 there are two figures 6 the second one should be corrected with 7
Authors' response:
Done, thanks.
Comment # 5:
The conclusions are very brief and it would be good to better explain the results and especially the impacts they may have on the management of the resource and agriculture.
Authors' response:
Done. The conclusion section was rewritten. Please see the lines between 347 and 370.
Reviewer 4 Report
Author Response
We thank you and the reviewer for your time and efforts in revising the manuscript.
Round 2
Reviewer 2 Report
I have seen the revised version and the manuscript is now acceptable
