Review Reports - Effects of Human Activities on Hydrological Components in the Yiluo River Basin in Middle Yellow River

Round 1

Reviewer 1 Report

The authors apply well-documented and proven models in their analysis of the Yiluo River Basin, documenting the proof of concept and the utility of using such models to evaluate the relative impacts of humans and natural climate variability on a regulated river in China. The impacts of the two impoundments can be clearly demonstrated. The use of a long term data set to calibrate and validate the hydrological models allows extension of the modelling to present day conditions. The modelling is sound and the conclusions adequately supported by the data, although the conclusions regarding inter-basin transfers may appear rather "foreign" to readers in Europe and North America where such concepts are regarded as unwarranted. (Nevertheless, in the greater scheme of river basin management, the suggestion is warranted in this situation.) The references are appropriate and the figures and tables useful and also appropriate. Minor language editing is recommended to ensure Standard English usage, particularly in the use of articles (a, an, the). Attention should also be given to tense and number (singular versus plural word forms).

Author Response

Comments and Suggestions for Authors: The authors apply well-documented and proven models in their analysis of the Yiluo River Basin, documenting the proof of concept and the utility of using such models to evaluate the relative impacts of humans and natural climate variability on a regulated river in China. The impacts of the two impoundments can be clearly demonstrated. The use of a long term data set to calibrate and validate the hydrological models allows extension of the modelling to present day conditions. The modelling is sound and the conclusions adequately supported by the data, although the conclusions regarding inter-basin transfers may appear rather "foreign" to readers in Europe and North America where such concepts are regarded as unwarranted. (Nevertheless, in the greater scheme of river basin management, the suggestion is warranted in this situation.) The references are appropriate and the figures and tables useful and also appropriate. Minor language editing is recommended to ensure Standard English usage, particularly in the use of articles (a, an, the). Attention should also be given to tense and number (singular versus plural word forms).

Reply: Thanks for your suggestions. The language of the manuscript has been refined and re-polished by a professional editor from Liwen Bianji, Edanz Group China (www.liwenbianji.cn./ac). The attachment contains the “Certificate of Language Editing”.

Author Response File: Author Response.pdf

Reviewer 2 Report

Revision water-467305

Title: Effects of human activities on hydrological components in the Yiluo River Basin in middle Yellow River

This study presents the results of a hydrologic simulation based on the SWAT model whereby the authors appreciate the variation in water balance components resulting from land use changes and water resource utilization behavior and policy in the Yiluo River Basin (middle Yellow River) in the period 1980-2010.

The study is not novel but is interesting given the scope, especially the evaluation of hydrologic impacts related to water resource utilization behavior and policy. However, the manuscript needs substantial revision because the modeling exercise is week compared with the study purpose. Please see my comments below.

CONCERNS

- In lines 158-160 the authors state “In addition, the human alternations of the natural stream flow are not accounted in the hydrological model since Luhun reservoir completion in 1965, because it is difficult to recreate undisturbed conditions, and its operation has limited impacts on conclusions in this study”. However, since the scope of the paper is to evaluate the impact of water resource utilization behavior and policy I believe this statement weakens the study. Current versions of ArcSWAT but especially other computer packages that also simulate the hydrology of anthropogenic catchments (e.g., Mike Basin) can easily account for the effects of dams, irrigation, water users, etc. The simulation presented in this study was rather conventional, where the authors simply have changed the land use map over the years and recalculated the hydrologic components. This can result in oversimplification and the authors need to justify that. In the Discussion the authors even recognize the potential impact of neglecting these contributions to the overall results. However, considering the context (study of an anthropogenic catchment) the authors should consider to go further and rework the model to include the aforementioned contributions.

- The discussion could be greatly improved. There are so many papers discussing various influences on river flow components that the authors could use to compare results (e.g., Santos et al., 2014). This would also help the authors justify their results if they opt not to improve the modeling exercise.

Santos, R.M.B., Sanches Fernandes, L.F., Moura, J.P., Pereira, M.G., & Pacheco F.A.L. (2014). The impact of climate change, human interference, scale and modeling uncertainties on the estimation of aquifer properties and river flow components. Journal of Hydrology, v. 519, p. 1297–1314.

MINOR POINT

- Lines 43-57. Hydrology and their components do not involve only the physical part. I believe a short mention is due to the chemical part because the same human activities strongly impact water quality and biodiversity in freshwater systems. For example, as regards land use changes the impacts on water quality can be tremendous when the change is inadequate in which case an environmental land use conflict is said to occur. Various studies reported the amplification of water quality degradation and biodiversity declines in response to these type of land use changes (Valle Junior et al., 2014, 2015; Santos et al., 2015; Pacheco et al., 2015; Pacheco and Sanches Fernandes, 2016) that could be acknowledged in the revised version.

Valle Junior, R.F., Varandas, S.G.P., Sanches Fernandes, L.F., & Pacheco, F.A.L. (2014). Groundwater quality in rural watersheds with environmental land use conflicts. Science of the Total Environment, v. 493, p. 812–827.

Valle Junior, R.F., Varandas, S.G.P., Pacheco, F.A.L., Pereira, V.R., Santos, C.F., Cortes, R.M.V., Fernandes, L.F.S. (2015). Impacts of land use conflicts on riverine ecosystems. Land Use Policy, v. 43, p. 48-62.

Santos, R.M.B., Sanches Fernandes, L.F., Pereira, M.G., Cortes R.M.V., Pacheco F.A.L. (2015). A framework model for investigating the export of phosphorus to surface waters in forested watersheds: implications to management. Science of the Total Environment, v. 536, p. 295-305.

Pacheco F.A.L., Santos, R.M.B., Sanches Fernandes, L.F., Pereira, M.G., Cortes R.M.V. (2015). Controls and forecasts of nitrate fluxes in forested watersheds: a view over mainland Portugal. Science of the Total Environment, v. 537, p. 421–440.

Pacheco F.A.L., Sanches Fernandes, L.F. (2016). Environmental land use conflicts in catchments: a major cause of amplified nitrate in river water. Science of the Total Environment, v. 548–549, p. 173–188.

RECOMMENDATION

Major revision

18 March 2019

Author Response

General comments:

Response: Thanks for your valuable comments and suggestions. The revised manuscript has been improved according to your comments and suggestions. In addition, the language of the manuscript has been refined and re-polished by a professional editor from Liwen Bianji, Edanz Group China (www.liwenbianji.cn./ac). The attachment contains the “Certificate of Language Editing”.

CONCERNS 1-1: In lines (158-160) the authors state “In addition, the human alternations of the natural stream flow are not accounted in the hydrological model since Luhun reservoir completion in 1965, because it is difficult to recreate undisturbed conditions, and its operation has limited impacts on conclusions in this study”. However, since the scope of the paper is to evaluate the impact of water resource utilization behavior and policy I believe this statement weakens the study.

Reply: Thanks a lot for the comments. We have carefully considered your proposal and deleted the sentence of "In addition, the human alternations of the natural stream flow are not accounted in the hydrological model since Luhun reservoir completion in 1965, because it is difficult to recreate undisturbed conditions, and its operation has limited impacts on conclusions in this study" in the lines of 169-172 in the revised manuscript.

Accordingly, we modified the statement in lines 336-340 in the revised version as following.

“Although human activities especially WRUBAP were not taken accounted in the calibration and validation of SWAT model, the model performance is satisfactory. And simulation not observation during the baseline period was compared with other scenarios to explore the effects of human activities.”

CONCERNS 1-2: Current versions of ArcSWAT but especially other computer packages that also simulate the hydrology of anthropogenic catchments (e.g., Mike Basin) can easily account for the effects of dams, irrigation, water users, etc. The simulation presented in this study was rather conventional, where the authors simply have changed the land use map over the years and recalculated the hydrologic components. This can result in oversimplification and the authors need to justify that. In the Discussion the authors even recognize the potential impact of neglecting these contributions to the overall results. However, considering the context (study of an anthropogenic catchment) the authors should consider to go further and rework the model to include the aforementioned contributions.

Reply: Thanks a lot for the comments. It is true current ArcSWAT is capable to simulate effect of dams, irrigation, water users, etc. They were defined as WRUBAP, and can be evaluated with conventional simulation method. But your suggestion is of great significance. It is worth assessing the individual or combined effects of dams, irrigation, water users, etc. as well as LUCC on hydrologic components. We will investigate them in further study.

CONCERNS 2: The discussion could be greatly improved. There are so many papers discussing various influences on river flow components that the authors could use to compare results. This would also help the authors justify their results if they opt not to improve the modeling exercise.

Reply: Thanks for your suggestions. We added some information about the influences on hydrological components: They are “which consequently affects the yield of phosphorus and nitrates [12, 53]” in line 347-348, “And investigation of LUCC impacts on water quality is an interesting topic.” in line 352-353, and “Hydrologic changes have important impacts on the local use of natural water [56]” in line 354-355 in the revised manuscript.

The documents of 12, 53 and 56 were added in the revised manuscript.

[12] Pacheco, F., et al., Controls and forecasts of nitrate yields in forested watersheds: a view over mainland Portugal. 2015. 537: p. 421-440.

[53] Santos, R., et al., A framework model for investigating the export of phosphorus to surface waters in forested watersheds: Implications to management. 2015. 536: p. 295-305.

[56] Santos, R.M.B., Sanches Fernandes, L.F., Moura, J.P., Pereira, M.G., & Pacheco F.A.L. (2014). The impact of climate change, human interference, scale and modeling uncertainties on the estimation of aquifer properties and river flow components. Journal of Hydrology, v. 519, p. 1297–1314.

MINOR POINT: Lines (43-57). Hydrology and their components do not involve only the physical part. I believe a short mention is due to the chemical part because the same human activities strongly impact water quality and biodiversity in freshwater systems. For example, as regards land use changes the impacts on water quality can be tremendous when the change is inadequate in which case an environmental land use conflict is said to occur. Various studies reported the amplification of water quality degradation and biodiversity declines in response to these type of land use changes.

Reply: Thanks for your suggestions. We added some reviews about impacts of human activities especially land use conflicts on water quality. “Numerous studies have shown that LUCC can have considerable impact on watershed hydrology in terms of water quantity and water quality.” in lines 44-46, and “Land use conflicts have impacts on concentration or yield of nitrates, phosphorus and sulphates etc. in both surface water and ground water [10-12]” in lines 50-52 were added in the revised manuscript.

And the three documents following were added in the revised manuscript.

[10] Junior, R.V., et al., Groundwater quality in rural watersheds with environmental land use conflicts. 2014. 493: p. 812-827.

[11] Junior, R.F.V., et al., Impacts of land use conflicts on riverine ecosystems. 2015. 43: p. 48-62.

[12] Pacheco, F., et al., Controls and forecasts of nitrate yields in forested watersheds: a view over mainland Portugal. 2015. 537: p. 421-440.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have extensively revised the manuscript in accordance with the suggestions provided. The paper is ready for publication.

Reviewer 2 Report

The authors responded well to my comments and suggestions the reason why I am now confident to approve the manuscript for publication