Evaluation of Individual Impacts of Human Activities on Streamflow Changes Using SWAT Model

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the manuscript titled “Evaluation of Individual Impact of Human Activities on Streamflow Changes Using the SWAT Model,” the authors utilize the physically-based, semi-distributed Soil and Water Assessment Tool (SWAT) to quantify the distinct impacts of human activities on streamflow variations in the Gamcheon watershed, South Korea. The study focuses on specific activities: upstream dam construction, discharge of treated sewage, and withdrawals from both stream and groundwater sources. The manuscript is well-written and easy to follow, and the methodology, though straightforward, is effective in isolating the individual contributions of these human impacts on watershed flow. I recommend publication of the manuscript, pending resolution of the following issues.

(1)     A constant daily groundwater use rate was treated as withdrawn from the HRU, where each groundwater well was located [29]. I recommend adding the well locations to Figure 1 for clarity.

(2)     Figure 7: The flow curves are difficult to distinguish. If the authors prefer not to use different colors, they could consider adding a zoomed inset on the side, focusing on the daily streamflow exceedance probability above 60%. Additionally, the y-axis title is not centered.

Author Response

Dear Reviewer,

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled “Evaluation of Individual Impact of Human Activities on Streamflow Changes Using SWAT Model” for publication in Water.

 

We appreciate the effort and time that you and the reviewers have dedicated for providing your valuable feedback on our manuscript. We are grateful to the reviewers for the valuable comments on our paper. Your insightful comments have led to improvements in the current version of the manuscript. We have carefully considered the comments of the reviewers and addressed them meticulously. We hope that the revised manuscript meets your high standards. We will be happy to address any further queries you may have. All the modifications in the manuscript are highlighted in red font. 

Please find an attached file of response to comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, the authors were to separate the individual human impacts on streamflow changes in the Gamcheon watershed in South Korea. The streamflow regime was disturbed by the construction of an upstream dam in 2013 and was continuously affected by the discharge of treated sewage water, as well as withdrawals of stream water and groundwater. To assess each of the impacting factors, a physical-based semi-distributed hydrological model, Soil and Water Assessment Tool (SWAT), was applied to the study area. The results showed that the combined effects of human activities on streamflow changes were not significant; however, the individual impacts were evident. The 10th lowest flow rate in a year, affected by stream water intake, groundwater pumping, dam operation, and treated sewage water discharge, was changed by -13.7 %, -54.0 %, 34.0 %, and 38.4 % relative to the natural flow, respectively. The Gamcheon Watershed was evaluated to balance the influence of human activity, ensuring streamflow was maintained at a natural level without causing a serious decrease.

Some specific comments:

1)     In the entire manuscript, there should be consistency with- and without dam, or natural, …

2)     Line 21: What does Q355 mean? Shouldn't it be abbreviated the first time?

3)     Line 41: “Dey al al." should be added year?

4)     Line 45: Please refer to and add reference: doi.org/10.1002/hyp.14834

5)     Lines 69 – 86: Please refer to and add reference: doi.org/10.1007/s00382-024-07319-7

6)     2.2 Model description

-         Cite information from previous studies or reports.

-          Introduce more information about Buhang dam, the main object of this study.

7)     Section: 2.3 Input data preparation

-          Line 172 – 174: Source of DEM?

-          Lines 198 – 200: “The total amount of stream water withdrawn from 15 points on Gamcheon Stream” Please show the 15-point location in Figure 1.

8)     Section: 2.4 Analysis procedure

-          Line 212: Should be changed “Sub-section 3.3” to “Sub-section 2.3).

-          Lines 212 – 215: Should have a validation period.

-          Lines: 215 – 216: Should further evaluate simulation results using a statistical indicator: PBIAS

-          Specify the method used to calibrate and validate the SWAT model.

9)     Section: 3.1 Model calibration

-          Table 1: In this study, the authors aim to assess the water intake, groundwater pumping, dam operation, and treated sewage water discharge. However, only 7 parameters are used to evaluate the sensitivity. The SWAT model has many sensitive parameters, and has been shown in the paper: doi.org/10.1007/s40808-017-0306-z

-          Lines 248 - 250: The NSE indicator is very high, please recheck it.

 

10)    Figure 9 does not show the monthly increase/decrease trend in agreement with Figure 8. The input data of these two figures are the same, just different units. Furthermore, in the conclusion section, the authors point out that streamflow change rates under individual human impacts at the outlet can reach 54%.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English could be improved to more clearly express the research.

Author Response

Dear Reviewer,

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled “Evaluation of Individual Impact of Human Activities on Streamflow Changes Using SWAT Model” for publication in Water.

 

We appreciate the effort and time that you and the reviewers have dedicated for providing your valuable feedback on our manuscript. We are grateful to the reviewers for the valuable comments on our paper. Your insightful comments have led to improvements in the current version of the manuscript. We have carefully considered the comments of the reviewers and addressed them meticulously. We hope that the revised manuscript meets your high standards. We will be happy to address any further queries you may have. All the modifications in the manuscript are highlighted in red font. 

Please find an attached file of response to comments.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

1) Lines 225 - 229: Need to rewrite to clarify the calibration and validation periods.

2) Lines 232 - 237: Need to clearly mention that the model has been calibrated and validated (just calibration is not enough).

3) Table 1: The authors need to clarify why they only chose 6 parameters in the SWAT model for calibration and validation. While there are other parameters that are also very sensitive.

4) Figure 8 and Figure 9: Do not insert legends on the chart.

Comments on the Quality of English Language

The authors need to rewrite some paragraphs to convey information more clearly to readers.

Author Response

Dear Reviewer,

Thank you for giving us the opportunity to submit a revised draft of our manuscript titled “Evaluation of Individual Impact of Human Activities on Streamflow Changes Using SWAT Model” for publication in Water.

 

We appreciate the effort and time that the reviewer has dedicated for providing valuable feedback on our manuscript. We are grateful to the reviewer for the valuable comments on our paper. Your insightful comments have led to improvements in the current version of the manuscript. We have carefully considered the comments of the reviewers and addressed them meticulously. We hope that the revised manuscript meets your high standards. We will be happy to address any further queries you may have. All the modifications in the manuscript are highlighted in red font. The point-by-point responses to your comments are in red font and are given the attached pdf file.

Author Response File: Author Response.pdf