Modeling and Evaluating Soil Salt and Water Transport in a Cultivated Land–Wasteland–Lake System of Hetao, Yellow River Basin’s Upper Reaches

Round 1

Reviewer 1 Report

The manuscript tried to clarify the soil salt and water transport process in a cultivated land -wasteland-lake system by using the Hydrus-1D model. Generally, the topic of the manuscript is interesting and met the scope of this journal. However, many inappropriate expressions or grammar mistakes throughout the whole manuscript should be amended before it is accepted.

1. Line 457-458, “For cultivated land, soil salt in the 0–20 cm soil zone of cultivated land decreased by 26%”, “cultivated land” appeared twice in a sentence. “of cultivated land” should be deleted.

2. Some of sentences in the manuscript were inappropriately expressed and hard to understand. Please check sentences throughout the whole text. For example, Line 414-416, Line 470-474. I don’t understand what are this sentence mean? Maybe authors can specify this part in discussion.

3. Line 496-497, the sentence “which caused salt in the deep soil zone accumulate” could be changed to “which caused salt accumulation in the deep soil zone”.

4. Line 24-25 and Line 593-594, “Salinization in the upper soil zone of wasteland and lake boundary was serious, while salinization in the deep soil zone of cultivated land was serious”. What is this “serious” mean? Please specify this sentence.

5. Line 41, change “foe” to “for”.

6. Line 360-361, the sentence “The simulated soil salt dynamics were also well matched with observations” appeared twice.

7. Table 7. what dose “A1, A2, A3” refer to?

8. Figure 5-7, what dose “DOY” refer to? Please specify them in the figures.

9. The discussion is very weak, and the explanations are mostly relying on the literature reports.

Author Response

Dear Professor:

    Thank you giving me valuable comments about the manuscript. According to your suggestions, the author has made a detailed revision. The specific modifications are described as follows:

1. Line 457-458, “For cultivated land, soil salt in the 0–20 cm soil zone of cultivated land decreased by 26%”, “cultivated land” appeared twice in a sentence. “of cultivated land” should be deleted.

Response 1：

According to reviewer’s suggestions, the author has made specific modifications as follows:

Thanks professor. The sentence “For cultivated land, soil salt in the 0–20 cm soil zone of cultivated land decreased by 26%”, there are two words: cultivated land. I decided to delete “of cultivated land” in the sentence. Therefore, it is changed into: For cultivated land, soil salt in the 0–20 cm soil zone of cultivated land decreased by 26%. I have revised it in my manuscript. Please check it.

2. Some of sentences in the manuscript were inappropriately expressed and hard to understand. Please check sentences throughout the whole text. For example, Line 414-416, Line 470-474. I don’t understand what are this sentence mean? Maybe authors can specify this part in discussion.

Response 2：

According to reviewer’s suggestions, the author has made specific modifications in my manuscript. Please check it.

4. Discussion

4.1 The effects of irrigation，groundwater dynamics, soil texture on soil water and salt distribution.

In recent years, with the implementation of water-conservation projects, the salt and water balance system that had been formed over many years has been disrupted. On the basis of the HYDRUS_1D model, soil water-salt transport and balance analysis in a cultivated land-wasteland- Lake system were estimated.

This study unveiled groundwater table and soil water content in the deep soil zone of wasteland and lake boundary rose during the irrigation period, and soil water content in the 60–100 cm soil zone of wasteland increased by 12%–15%. Li et al (2010) showed that the groundwater lateral flow between cultivated land and wasteland was engendered after irrigation, and found that soil water content in the 20-70 cm soil zone of wasteland increased by 4%–11%[17]. Our result was larger than that of Li, because it is difficult to increase moisure in the 20-40cm soil zone by capillary action. This study found that the utilization efficiency of irrigation was 78%. Wang et al(2020) based on δD and δ18O isotope revealed that the utilization efficiency of irrigation was 82%[41]. Results showed there was a sharp decline in soil EC with irrigation, after which it gradually increased prior to the subsequent next irrigation. Hao et al(2015) showed that irrigation water diluted the soil solution, and the salt was leached to the deep soil zone[42]. He et al(2017) used Hydrus_1D model to study the irrigated cropping system, and showed that Freshwater irrigation can leach out salts from the 100 cm root-profile depth[43].Tong et al(2018) found that mean soil salt reduction rate under drip irrigation and sub-surface pipe drainage was 19.30% and 58.12%[44].This study found that soil salt in the 0–20 cm soil zone of cultivated land decreased by 20~26% during irrigation period. The salt reduction rate of border irrigation is higher than that of drip irrigation, but lower than that of sub-surface pipe drainage. This study found that the salt storage in the 1-m soil zone of cultivated land, wasteland, and lake boundary had an increasing trend, which was average increase of 19%, 27%, and 37%, respectively. Wang et al. (2021) studied soil water and salt transport process during the sand dune-wasteland-lake system, and found that the salt accumulation rate of wasteland in the 1m soil zone is 25% during the growth period[45]. Their study results are similar, which indicated that wasteland was in a state of salt accumulation during the growth period. During the growth period, the lake boundary was in a state of salt accumulation.Those factors, including shallow groundwater depth, sandy loam in the 0–20 cm soil zone, and sand in the 20–100 cm soil zone, are benefit to salt accumulated in the upper soil zone, whereas those factors were not good for the upward movement of salt and water due to weak capillary action. Chen et al.( 2010) found that it is significant and necessary for salinity control to conduct a big flood irrigation to decline the salt accumulation after harvest[46].

4.2 Soil water and salt balance analysis

we revealed that, the deep percolation of cultivated land was 34%–40% of the applied water (rainfall and irrigation). Ren et al. (2018) pointed out that about 36% of the total applied water was stored in shallow groundwater[31], which indicated that results of this study was acceptable. Ren et al. (2016) unveiled that capillary rise in watermelon, sunflower, and maize fields accounted for over 45%, 24% and 33% of their respective total evapotranspiration[5]. Xu et al. (2015) found that the cumulative capillary rise could reach 40% of evapotranspiration when groundwater depth was set at 100 cm[47]. We found the capillary rise of cultivated land, wasteland, and lake boundary was 24%, 29%–35%, and 62%–68% of their own evapotranspiration, respectively. These results were similar with prior studies, which were credible. Capillary rise of Lake boundary was larger than that of wasteland. Since groundwater table of lake boundary was 30cm~120cm during the growth period (Fig. 3 and 4). Ren et al. (2019 ) pointed out that 40% of the total salt was retained in wasteland and 39% in farmland[48]. Li et al. (2010) showed wasteland was in a state of salt accumulation, and salt accumulation in the upper soil zone was the most serious[17]. Based on the previous research, we further found that the salt accumulation in the upper soil zone of cultivated land, wasteland, and the lake boundary was 13%, 37%, and 48%, respectively, and in the deep soil zone, it was 34%, 15%, and 13%, respectively, which was significant to prevent soil salinization for Hetao Irrigation District. This study suggested some measures should be taken to reduce the salt content in the upper soil zone of wasteland and lake boundary and in the deep soil zone of cultivated land to prevent soil salinization.

3. Line 496-497, the sentence “which caused salt in the deep soil zone accumulate” could be changed to “which caused salt accumulation in the deep soil zone”.

Response 3：

According to reviewer’s suggestions, the author has made specific modifications as follows:

Yes，thanks professor. It is a grammer mistake. I have changed it into” During the irrigation period, the groundwater salt of wasteland was transported to the lakes, which caused salt accumulation in the deep soil zone”. Please check it.

4. Line 24-25 and Line 593-594, “Salinization in the upper soil zone of wasteland and lake boundary was serious, while salinization in the deep soil zone of cultivated land was serious”. What is this “serious” mean? Please specify this sentence.

Response 4：

According to reviewer’s suggestions, the author has made specific modifications as follows:

Thanks professor. Your question is very valuable, I am sorry for you that the meaning of this sentence is vauge. Actually, I want to express that soil salt content in the upper soil zone of wasteland and lake boundary was high, while soil salt content in the deep soil zone of cultivated land was high”, Soil salinization in the upper soil zone of wasteland and lake boundary was serious.

Wasteland and lake boundary are not affected by irrigation and only seriously affected by evaporation. The salt in groundwater and deep soil zone of wasteland and lake boundary was transported to the surface soil zone with capillary action, therefore soil salt content was high.For cultivated land, the salt in the upper soil layer is leached into the deep soil layer by irrigation, therefore, soil salt content in the deep siol layer was high.

I decided to change it into: Soil salt content in the upper soil zone of wasteland and lake boundary was high, while soil salt content in the deep soil zone of cultivated land was high. Soil Salinization in the upper soil zone of wasteland and lake boundary was serious. Please check it in the manuscript.

5. Line 41, change “foe” to “for”.

Response 5：

I am sorry for my carelessness. Ok professor, I have changed it in my manuscript. Please check it.

6. Line 360-361, the sentence “The simulated soil salt dynamics were also well matched with observations” appeared twice.

Response 6：

Yes professor. I have deleted one sentence in my manuscript. In order to improve the paper, the manuscript was revised many times in revision version before I submit it to Sustainability Journal, therefore there was a mistake in the paper. I don’t find this sentence appeared twice, I am sorry for my carelessness. Ok professor, I have changed it in my manuscript. Please check it.

7. Table 7. what dose “A1, A2, A3” refer to?

Response 7：

According to reviewer’s suggestions, the author has made specific modifications as follows:

Thank you for pointing out the avoidable mistake.“A1, A2, A3” refers to A, B, C respectively, as shown in figure 2. A. B and C represent cultivated land, wasteland and lake boundary respectively. In the baginning, I design A1, A2, A3 represent cultivated land, wasteland and lake boundary respectively, and the whole paepr about cultivated land, wasteland and lakes boundary are marked by A1, A2 and A3 instead of A B C. However, the tutor thought that A1, A2 and A3 were not highly recognized and easy to be confused, so they were uniformly revised to A, B and C. Due to my negligence, A1, A2 and A3 in table 7 were not replaced with A, B and C. Sorry, Professor. I have revised in my manuscript, please check it. Thanks.

8. Figure 5-7, what dose “DOY” refer to? Please specify them in the figures.

Response 8：

According to reviewer’s suggestions, the author has made specific modifications as follows:

DOY means“Day of Year”, as shown in figure below，I make May 1st is the first day of study, for example: on September 20, it was the 113d of the study, Maybe it is difficult for reader to underatand. I decided that I will revise DOY into date. Maybe it is easy to understand.As shown in below Figure. I have changed in my manuscript.

 

9. The discussion is very weak, and the explanations are mostly relying on the literature reports.

Reponse 9:

According to reviewer’s suggestions, the author has made specific modifications as follows:

4. Discussion

4.1 The effects of irrigation，groundwater dynamics, soil texture on soil water and salt distribution.

In recent years, with the implementation of water-conservation projects, the salt and water balance system that had been formed over many years has been disrupted. On the basis of the HYDRUS_1D model, soil water-salt transport and balance analysis in a cultivated land-wasteland- Lake system were estimated.

This study unveiled groundwater table and soil water content in the deep soil zone of wasteland and lake boundary rose during the irrigation period, and soil water content in the 60–100 cm soil zone of wasteland increased by 12%–15%. Li et al (2010) showed that the groundwater lateral flow between cultivated land and wasteland was engendered after irrigation, and found that soil water content in the 20-70 cm soil zone of wasteland increased by 4%–11%[17]. Our result was larger than that of Li, because it is difficult to increase moisure in the 20-40cm soil zone by capillary action. This study found that the utilization efficiency of irrigation was 78%. Wang et al(2020) based on δD and δ18O isotope revealed that the utilization efficiency of irrigation was 82%[41]. Results showed there was a sharp decline in soil EC with irrigation, after which it gradually increased prior to the subsequent next irrigation. Hao et al(2015) showed that irrigation water diluted the soil solution, and the salt was leached to the deep soil zone[42]. He et al(2017) used Hydrus_1D model to study the irrigated cropping system, and showed that Freshwater irrigation can leach out salts from the 100 cm root-profile depth[43].Tong et al(2018) found that mean soil salt reduction rate under drip irrigation and sub-surface pipe drainage was 19.30% and 58.12%[44].This study found that soil salt in the 0–20 cm soil zone of cultivated land decreased by 20~26% during irrigation period. The salt reduction rate of border irrigation is higher than that of drip irrigation, but lower than that of sub-surface pipe drainage. This study found that the salt storage in the 1-m soil zone of cultivated land, wasteland, and lake boundary had an increasing trend, which was average increase of 19%, 27%, and 37%, respectively. Wang et al. (2021) studied soil water and salt transport process during the sand dune-wasteland-lake system, and found that the salt accumulation rate of wasteland in the 1m soil zone is 25% during the growth period[45]. Their study results are similar, which indicated that wasteland was in a state of salt accumulation during the growth period. During the growth period, the lake boundary was in a state of salt accumulation.Those factors, including shallow groundwater depth, sandy loam in the 0–20 cm soil zone, and sand in the 20–100 cm soil zone, are benefit to salt accumulated in the upper soil zone, whereas those factors were not good for the upward movement of salt and water due to weak capillary action. Chen et al.( 2010) found that it is significant and necessary for salinity control to conduct a big flood irrigation to decline the salt accumulation after harvest[46].

4.2 Soil water and salt balance analysis

we revealed that, the deep percolation of cultivated land was 34%–40% of the applied water (rainfall and irrigation). Ren et al. (2018) pointed out that about 36% of the total applied water was stored in shallow groundwater[31], which indicated that results of this study was acceptable. Ren et al. (2016) unveiled that capillary rise in watermelon, sunflower, and maize fields accounted for over 45%, 24% and 33% of their respective total evapotranspiration[5]. Xu et al. (2015) found that the cumulative capillary rise could reach 40% of evapotranspiration when groundwater depth was set at 100 cm[47]. We found the capillary rise of cultivated land, wasteland, and lake boundary was 24%, 29%–35%, and 62%–68% of their own evapotranspiration, respectively. These results were similar with prior studies, which were credible. Capillary rise of Lake boundary was larger than that of wasteland. Since groundwater table of lake boundary was 30cm~120cm during the growth period (Fig. 3 and 4). Ren et al. (2019 ) pointed out that 40% of the total salt was retained in wasteland and 39% in farmland[48]. Li et al. (2010) showed wasteland was in a state of salt accumulation, and salt accumulation in the upper soil zone was the most serious[17]. Based on the previous research, we further found that the salt accumulation in the upper soil zone of cultivated land, wasteland, and the lake boundary was 13%, 37%, and 48%, respectively, and in the deep soil zone, it was 34%, 15%, and 13%, respectively, which was significant to prevent soil salinization for Hetao Irrigation District. This study suggested some measures should be taken to reduce the salt content in the upper soil zone of wasteland and lake boundary and in the deep soil zone of cultivated land to prevent soil salinization.

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript focused on the soil water consumption and salt accumulation in a case study. It well-organized and well-written. However, a flowchart is necessary to describe the methodology, more clearly. Moreover, please discuss on limitations of your study in the conclusion section.

Author Response

Reviewer2#

The manuscript focused on the soil water consumption and salt accumulation in a case study. It well-organized and well-written. However, a flowchart is necessary to describe the methodology, more clearly. Moreover, please discuss on limitations of your study in the conclusion section.

1. It well-organized and well-written. However, a flowchart is necessary to describe the methodology, more clearly.

Response 1：

According to reviewer’s suggestions, the author has made specific modifications as follows:

Thank you professor, giving me wonderful suggestion. I have added the flowchart in my manuscript. The flowchart made the study more clear.

Based on the collected data of soil, groundwater, meteorological, crop growth, irrigation, this research studied the water and salt transport of cultivated land, wasteland and lake boundary with HYDRUS model. The study flowchart is as follows:

Study flowchart

Note ET0: reference crop evapotranspiration(cm d ^-1); ET_p : potential evapotranspiration (cm d ^-1), E_p: potential evaporation (cm d ^-1); T_p: potential transpiration (cm d ^-1), K_c: Crop coefficient

 

2. Please discuss on limitations of your study in the conclusion section.

Response 2:

According to reviewer’s suggestions, the author has made specific modifications as follows:

5. Conclusion

The Hydrus-1D model was successfully used to evaluate the soil salt and water transportcharacteristics of cultivated land, wasteland, and the lake boundary in the HID. The simulations of the model provide a good representation of measurements. The conclusions are as follows:

(1) On the 5th day after irrigation, the soil water storage increment of cultivated land, wasteland and lake boundary is 69mm~81mm, 36~51mm and 9~22mm,respectively, especially, soil water content in the 60–100 cm soil zone of wasteland increased by 12%–15%. On the 87th day after irrigation, the water storage of cultivated land, wasteland and lake boundary decreased by 186 mm, 150 mm, 60mm, soil water content in the 0–60 cm soil zone of cultivated land and wasteland decreased by 34%–56%, by 20%–45%. 

(2) The deep percolation of cultivated land was 34%–40% of the applied water (rainfall and irrigation). The capillary rise of cultivated land, wasteland, and lake boundary was 24%, 29%–35%, and 62%–68% of their own evapotranspiration, respectively.

(3) In the whole growth period, the salt storages in the 1-m soil zone of cultivated land, wasteland, and the lake boundary on average increased by 19%, 27%, and 37%, respectively. the salt accumulation in the upper soil zone of cultivated land, wasteland, and the lake boundary was 13%, 37%, and 48%. Soil Salinization in the upper soil zone of wasteland and lake boundary was serious, so some measures should be taken to reduce the salt content to prevent soil salinization.

(4) Since study scale of cultivated land, wasteland and lake systems was small, the simulation accuracy of regional hydrological model is limited. It is necessary to expand the study area and establish a large hydrological monitoring network to study hydrological process in the future.

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

The presented manuscript titled „Modeling and evaluating soil salt and water transport in a cultivated land-wasteland -lake system of Hetao, Yellow River Basin’s upper reaches” contains valuable results. Generally, manuscript is well-written. However, I have fund some imperfections, which- in my opinion- should be corrected or clarified before an eventual publication.

1.       I suggest to add main conclusion in Abstract section.

2.       Figures and Tables should be self-explanatory. Please add the meaning of abreviations and acronyms in the captions.

3.       In my opinion the substantial results are poorly discussed with literature of subject.

4.       Chapter Conclusions looks like summary of results. Please formulate conclusions from investigations and add the proposed further directions of studies.

5.       Please look into belowe mentioned publications. Perhaps, some of them will be useful in the manuscript imrovements:

·         Heng, T., Liao, R., Wang, Z. et al. 2018. Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China. J. Arid Land 10, 932–945.

·         Yugang Wang, Caiyun Deng, Yan Liu, Ziru Niu, Yan Li, 2018. Identifying change in spatial accumulation of soil salinity in an inland river watershed, China, Science of The Total Environment, 621,177-185.

·         He, K.; Yang, Y.; Yang, Y.; Chen, S.; Hu, Q.; Liu, X.; Gao, F. HYDRUS Simulation of Sustainable Brackish Water Irrigation in a Winter Wheat-Summer Maize Rotation System in the North China Plain. Water 2017, 9, 536. https://doi.org/10.3390/w9070536

·         Weiping Chen, Zhenan Hou, Laosheng Wu, Yongchao Liang, Changzhou Wei,2010. Evaluating salinity distribution in soil irrigated with saline water in arid regions of northwest China, Agricultural Water Management, 97,12, 2001-2008.

Author Response

Dear Professor:

    Thank you giving me valuable comments about the manuscript. According to your suggestions, the author has made a detailed revision. The specific modifications are described as follows:

1. I suggest to add main conclusion in Abstract section.

Response 1：

According to reviewer’s suggestions, the author has made specific modifications as follows:

With the implementation of water-conservation projects in Hetao Irrigation District (HID), great changes have taken place in eco-hydrological process. A cultivated land-wasteland-lake system in the upper Yellow River Basin (YRB) was chosen to study soil salt and water transport process with Hydrus-1D model. The model parameters are calibrated and validated by measured soil salt and water data. Measured value is a good agreement with simulated value. The results showed, in the whole growth period, the deep percolation of cultivated land was 34%–40% of the total applied water (rainfall and irrigation). The capillary rise of cultivated land, wasteland, and lake boundary was 24%, 29%–35%, and 62%–68% of their own evapotranspiration, respectively. The capillary rise of lake boundary was about 2 times that of wasteland, 2.6 times that of cultivated land. The salt storages in the 1 m soil zone of lake boundary was more 10% and 18% than that of wasteland and cultivated land, respectively. The salt of capillary rise in the lake boundary exceeded that of wasteland by a factor of 3. The salt accumulation in the upper soil zone of cultivated land, wasteland, and the lake boundary was 13%, 37%, and 48%. Soil Salinization in the upper soil zone of wasteland and lake boundary was serious,and some measures should be taken to reduce the salt content to prevent soil salinization. The results act as a theoretical basis for eco-hydrology control of the HID.

2. Figures and Tables should be self-explanatory. Please add the meaning of abreviations and acronyms in the captions.

Response 2：

Ok, professor. I have added the meaning of breviations and acronyms in my manuscript. Please check it.

3. In my opinion the substantial results are poorly discussed with literature of subject.

Response 3：

According to reviewer’s suggestions, the author has made specific modifications as follows:

4. Discussion

4.1 The effects of irrigation，groundwater dynamics, soil texture on soil water and salt distribution.

In recent years, with the implementation of water-conservation projects, the salt and water balance system that had been formed over many years has been disrupted. On the basis of the HYDRUS_1D model, soil water-salt transport and balance analysis in a cultivated land-wasteland- Lake system were estimated.

This study unveiled groundwater table and soil water content in the deep soil zone of wasteland and lake boundary rose during the irrigation period, and soil water content in the 60–100 cm soil zone of wasteland increased by 12%–15%. Li et al (2010) showed that the groundwater lateral flow between cultivated land and wasteland was engendered after irrigation, and found that soil water content in the 20-70 cm soil zone of wasteland increased by 4%–11%[17]. Our result was larger than that of Li, because it is difficult to increase moisure in the 20-40cm soil zone by capillary action. This study found that the utilization efficiency of irrigation was 78%. Wang et al(2020) based on δD and δ18O isotope revealed that the utilization efficiency of irrigation was 82%[41]. Results showed there was a sharp decline in soil EC with irrigation, after which it gradually increased prior to the subsequent next irrigation. Hao et al(2015) showed that irrigation water diluted the soil solution, and the salt was leached to the deep soil zone[42]. He et al(2017) used Hydrus_1D model to study the irrigated cropping system, and showed that Freshwater irrigation can leach out salts from the 100 cm root-profile depth[43].Tong et al(2018) found that mean soil salt reduction rate under drip irrigation and sub-surface pipe drainage was 19.30% and 58.12%[44].This study found that soil salt in the 0–20 cm soil zone of cultivated land decreased by 20~26% during irrigation period. The salt reduction rate of border irrigation is higher than that of drip irrigation, but lower than that of sub-surface pipe drainage. This study found that the salt storage in the 1-m soil zone of cultivated land, wasteland, and lake boundary had an increasing trend, which was average increase of 19%, 27%, and 37%, respectively. Wang et al. (2021) studied soil water and salt transport process during the sand dune-wasteland-lake system, and found that the salt accumulation rate of wasteland in the 1m soil zone is 25% during the growth period[45]. Their study results are similar, which indicated that wasteland was in a state of salt accumulation during the growth period. During the growth period, the lake boundary was in a state of salt accumulation.Those factors, including shallow groundwater depth, sandy loam in the 0–20 cm soil zone, and sand in the 20–100 cm soil zone, are benefit to salt accumulated in the upper soil zone, whereas those factors were not good for the upward movement of salt and water due to weak capillary action. Chen et al.( 2010) found that it is significant and necessary for salinity control to conduct a big flood irrigation to decline the salt accumulation after harvest[46].

4.2 Soil water and salt balance analysis

we revealed that, the deep percolation of cultivated land was 34%–40% of the applied water (rainfall and irrigation). Ren et al. (2018) pointed out that about 36% of the total applied water was stored in shallow groundwater[31], which indicated that results of this study was acceptable. Ren et al. (2016) unveiled that capillary rise in watermelon, sunflower, and maize fields accounted for over 45%, 24% and 33% of their respective total evapotranspiration[5]. Xu et al. (2015) found that the cumulative capillary rise could reach 40% of evapotranspiration when groundwater depth was set at 100 cm[47]. We found the capillary rise of cultivated land, wasteland, and lake boundary was 24%, 29%–35%, and 62%–68% of their own evapotranspiration, respectively. These results were similar with prior studies, which were credible. Capillary rise of Lake boundary was larger than that of wasteland. Since groundwater table of lake boundary was 30cm~120cm during the growth period (Fig. 3 and 4). Ren et al. (2019 ) pointed out that 40% of the total salt was retained in wasteland and 39% in farmland[48]. Li et al. (2010) showed wasteland was in a state of salt accumulation, and salt accumulation in the upper soil zone was the most serious[17]. Based on the previous research, we further found that the salt accumulation in the upper soil zone of cultivated land, wasteland, and the lake boundary was 13%, 37%, and 48%, respectively, and in the deep soil zone, it was 34%, 15%, and 13%, respectively, which was significant to prevent soil salinization for Hetao Irrigation District. This study suggested some measures should be taken to reduce the salt content in the upper soil zone of wasteland and lake boundary and in the deep soil zone of cultivated land to prevent soil salinization.

4. Chapter Conclusions looks like summary of results. Please formulate conclusions from investigations and add the proposed further directions of studies.

Response 4：

According to reviewer’s suggestions, the author has made specific modifications as follows:

The Hydrus-1D model was successfully used to evaluate the soil salt and water transportcharacteristics of cultivated land, wasteland, and the lake boundary in the HID. The simulations of the model provide a good representation of measurements. The conclusions are as follows:

(1) On the 5th day after irrigation, the soil water storage increment of cultivated land, wasteland and lake boundary is 69mm~81mm, 36~51mm and 9~22mm,respectively, especially, soil water content in the 60–100 cm soil zone of wasteland increased by 12%–15%. On the 87th day after irrigation, the water storage of cultivated land, wasteland and lake boundary decreased by 186 mm, 150 mm, 60mm, soil water content in the 0–60 cm soil zone of cultivated land and wasteland decreased by 34%–56%, by 20%–45%. 

(2) The deep percolation of cultivated land was 34%–40% of the applied water (rainfall and irrigation). The capillary rise of cultivated land, wasteland, and lake boundary was 24%, 29%–35%, and 62%–68% of their own evapotranspiration, respectively.

(3) In the whole growth period, the salt storages in the 1-m soil zone of cultivated land, wasteland, and the lake boundary on average increased by 19%, 27%, and 37%, respectively. the salt accumulation in the upper soil zone of cultivated land, wasteland, and the lake boundary was 13%, 37%, and 48%. Soil Salinization in the upper soil zone of wasteland and lake boundary was serious, so some measures should be taken to reduce the salt content to prevent soil salinization.

(4) Since study scale of cultivated land, wasteland and lake systems was small, the simulation accuracy of regional hydrological model is limited. It is necessary to expand the study area and establish a large hydrological monitoring network to study hydrological process in the future.

5.    Please look into belowe mentioned publications. Perhaps, some of them will be useful in the manuscript imrovements:

• Heng, T., Liao, R., Wang, Z. et al. Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China. J. Arid Land10, 932–945.
• Yugang Wang, Caiyun Deng, Yan Liu, Ziru Niu, Yan Li, 2018. Identifying change in spatial accumulation of soil salinity in an inland river watershed, China, Science of The Total Environment, 621,177-185.
• He, K.; Yang, Y.; Yang, Y.; Chen, S.; Hu, Q.; Liu, X.; Gao, F. HYDRUS Simulation of Sustainable Brackish Water Irrigation in a Winter Wheat-Summer Maize Rotation System in the North China Plain. Water 2017, 9, 536. https://doi.org/10.3390/w9070536
• Weiping Chen, Zhenan Hou, Laosheng Wu, Yongchao Liang, Changzhou Wei,2010. Evaluating salinity distribution in soil irrigated with saline water in arid regions of northwest China, Agricultural Water Management, 97,12, 2001-2008.

Response 5：

    Thank you for providing me useful literatures. I have cited them in the discussion section in my manuscript. Please check it.

Reference

1. Xue, J., Huo, Z., Shuai Wang, S. 2020. A novel regional irrigation water productivity model coupling irrigation- and drainage-driven soil hydrology and salinity dynamics and shallow groundwater movement in arid regions in China. Hydrol. Earth Syst. Sci., 24, 2399–2418, 2020.
2. Chang, X., Gao, Z., Wang, S., & Chen, H. 2019. Modelling long-term soil salinity dynamics using Saltmod in Hetao irrigation district, china. Computers and Electronics in Agriculture, 156, 447-458.
3. Luo, Y., Sophocleous, M., 2010. Seasonal groundwater contribution to crop-water use assessed with lysimeter observations and model simulations. J. Hydrol. (Amst) 389 (3), 325–335.
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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

   The authors have made appropriate revisions and corrections on the manuscript, I recommend it for publication. 

comments: table1, table4, table 6 and table 7: Authors should unify the table layout throughout the manuscript, for exemple, (1)'land use type' was used in table 6, whereas  'land type' was used in table7.(2) A, B and C in table4, table 1 and table 6 were introduced to represent cultivated land, wasteland and lake boundary respectively, whereas table 6 not. 

Author Response

Dear Professor:

    Thank you giving me valuable comments about the manuscript. According to your suggestions, the author has made a detailed revision. The specific modifications are described as follows:

comments: table1, table4, table 6 and table 7: Authors should unify the table layout throughout the manuscript, for exemple, (1)'land use type' was used in table 6, whereas  'land type' was used in table7.(2) A, B and C in table4, table 1 and table 6 were introduced to represent cultivated land, wasteland and lake boundary respectively, whereas table 6 not. 

Response ：

According to reviewer’s suggestions, the author has made specific modifications as follows:

Thank you for giving me valuable suggestions to help me improve my manascript. Yes, the content in the Table 1, Table4, Table6 and Table7 are nor uniform, thanks professor helping me point out this problem. According to your suggestions, I have changed it in my manuscript. Please check it.

Table 1. Physical characteristics of soil of the experimental area.

Site	Depth of soil (cm)	The distribution of soil particle sizes (%）
		Clay （<0.02mm）	Silt （0.02~0.5mm）	Sand （0.5~2mm）	Bulk soil density (g cm-3)	Ks(Saturated hydraulic conductivity (cm d-1)	(Saturated water content) (cm3cm-3)
A	0~300	3.16	45.28	51.56	1.51	19.67	0.31
B	0~80	2.18	42.65	55.17	1.53	22.10	0.36
	80~300	2.49	7.68	89.83	1.61	230.84	0.33
C	0~20	5.61	14.32	80.06	1.52	197.76	0.38
	20~300	0.42	5.88	94.12	1.62	315.12	0.31

 

Table 4. Values assigned to the van parameters of the Genuchten–Mualem model and lengths of dispersion among different soil zones.

Site	Depths (cm)	Residual soil content qr (cm3cm-3)	Saturated soil content qs(cm3cm-3)	Shape parameter a(-)	Empirical parameter n(-)	Saturated hydraulic conductivity/ Ks(cm d-1)	molecular diffusion coefficient l(-)	dispersion coefficient L(cm)
A	Starting values
	0~200	0.0271	0.312	0.035	1.12	19.67	0.7	20
	Calibrated values
	0~200	0.0421	0.3911	0.006	8.11	21.12	3.0	15
B	Starting values
	0~80	0.0262	0.36	0.043	1.12	22.1	0.7	20
	80~200	0.0442	0.33	0.038	2.05	230.84	1.0	10
	Calibrated values
	0~80	0.0412	0.52	0.044	1.74	22.1	2.0	20
	80~200	0.0521	0.51	0.032	1.82	230.84	2.0	20
C	Starting values
	0~20	0.0422	0.38	0.043	1.79	198.12	0.7	20
	20~200	0.0351	0.31	0.036	3.19	315.57	1	10
	Calibrated values
	0~80	0.0422	0.41	0.042	1.51	25	0.5	15
	80~200	0.0351	0.39	0.036	1.23	242	0.5	25

 

Table 6. Values obtained for model goodness-of-fit statistics for calibration and verification.

Items	Site	Items	R2	b	RMSE (cm3 cm-3 or g L-1)	MRE (%)
Calibration (2018)	A	Soil water content	0.75	1.0	0.06	4.89
		soil salinity concentration	0.89	0.95	0.08	-0.91
	B	Soil water content	0.88	1.02	0.02	-0.43
		soil salinity concentration	0.90	0.96	0.09	-2.23
	C	Soil water content	0.90	0.9	0.01	0.15
		soil salinity concentration	0.91	0.97	0.091	-1.26
Verification (2019)	A	Soil water content	0.92	1.0	0.01	-0.31
		soil salinity concentration	0.56	1.0	0.15	4.43
	B	Soil water content	0.90	0.99	0.02	-0.92
		soil salinity concentration	0.88	0.98	0.16	-0.013
	C	Soil water content	0.91	1.01	0.04	0.63
		soil salinity concentration	0.89	1.02	0.34	-0.89

 

Table 7. Salt and water balance in the 0–100 cm soil profile during the simulation period from June 1st to October 1st in 2018 and 2019.

Year	Site	Soil water /Salt	Precipitation	Irrigation	Initial storage	Final storage	Percolation	Capillary rise	Evaporation	Transpiration
2018	A	Soil water (mm)	109.6	200	540	374	105	118	166	324
		Salt (g m-2)	—	120	7743	10007	2012	2291	—	—
	B	Soil water (mm)	109.6	—	586	383	20	123	423	—
		Salt (g m-2)	—	—	7935	11172	460	2336	—	—
	C	Soil water (mm)	109.6	—	610	530	21	271	440	—
		Salt (g m-2)	—	—	9970	15553	622	7370	—	—
2019	A	Soil water (mm)	64.88	210	583	306	110	140	202	380
		Salt (g m-2)	—	126	7222	8459	1568	1904	—	—
	B	Soil water (mm)	64.88	—	655	394	50	151	432	—
		Salt (g m-2)	—	—	9420	12666	934	2702	—	—
	C	Soil water (mm)	64.88	—	649	531	47	289	425	—
		Salt (g m-2)	—	—	11318	18196	1228	7291	—	—

 

Author Response File: Author Response.pdf

Reviewer 2 Report

My previous comments have been considered. 

Author Response

Dear Professor:

    Thank you giving me valuable comments about the manuscript. According to your suggestions, the author has made a detailed revision. The specific modifications are described as follows:

1. My previous comments have been considered. 

Reponse1:

Ok,Professor. Thank you for giving me valuable questions to help me improve my manascript.

Finally, I hope that you have a good day forever.

Author Response File: Author Response.docx