Estimation of Runoff and Sediment Yield in Response to Temporal Land Cover Change in Kentucky, USA

Round 1

Reviewer 1 Report

General Comments:

The authors assess potential differences in runoff and sediment attributed to land cover changes using the SWAT model. The results are not especially surprising given knowledge of general watershed processes. The authors do not emphasize it upfront, but this appears to be a somewhat data-sparse watershed (in relation to sediment data) and presents an interesting way of providing sediment data to the model. I think the paper would be strengthened by highlighting that fact and including explanation and discussion justifying the inclusion of the process and how it impacts the evaluation of the results (for scientific and non-scientific audiences).

It isn’t absolutely necessary, but I think some description of why SWAT was implemented here as opposed to other mechanistic or conceptual models would be appreciated. I wasn’t clear if this was primarily to fill the SWAT database or if this was assumed to be the best approach to answer some local/regional question on changes in hydrologic response to land use change.

 

Comments

Lines 59-82: If the information is available, description of the type of mining that is predominant in the region is useful (surface, mountain-top removal, contour, pit, etc.). I also assume there is a literature on the more specific impacts of whatever the predominant mine operation type is on surface and subsurface hydrologic pathways?

 

Line 80-82: What direction are the impacts on soil, nitrogen and phosphorus export? Since mining and mine reclamation are the primary impacts being evaluated in this paper, providing the reader with a better understanding of the assumed mechanistic processes of mines and mine reclamation on hydrology and water quality would be appreciated.

 

Section 2.2.1: Please include the USGS NWIS gages used.

 

Line 195-196: If I understand correctly, the authors fit a LOADEST model using 1979-1981 streamflow/sediment data and used that model to predict sediment concentrations/loads that were used in the calibration/validation period of the SWAT model? I can understand the pragmatic reasons for doing so, the authors are primarily interested in the relative changes in SWAT output and sensitivity in responses to land use changes and not necessarily the absolute loads. However, there is a major assumption that the sediment rating curve developed by LOADEST is consistent between both time periods. Also, because there is little “noise” in the predicted outputs from LOADEST (it fits only on flow and time, I would assume this inflates model evaluation metrics relative to using measured environmental data for calibration and validation. This doesn’t invalidate the work, but should be stated up front for readers to understand that this was an application of SWAT to a watershed with very sparse water quality data.

Further, since it is part of the data generating process, it would be useful to report the LOADEST output. Which model was fit and how well did it perform in regards to accuracy and bias.

 

Line 270-274: Be clear that observed streamflow and LOADEST predicted sediment was used.

 

Line 273-274: The fact streamflow is the assumed primary variable and the majority of sediment loads are typically transported during high streamflow events can be highlighted earlier to better warrant the use of LOADEST.

Figure 12: I don’t think this is needed. It is redundant with Table 6 and Figure 11.

 

Discussion: I there anything that should be interpreted from the sensitivity analysis that is applicable to the modelled watershed and mine-remediation?

Author Response

Please see the attachment 

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors, Thanks for drafting this manuscript. I have had the pleasure of going through it and I firmly believe the paper has potential for publication in the Land journal. However, there are many flaws and important details left out which I suggest the authors go through carefully, and address point-by-point responses and edits to the original paper. Find attached all my comments. I suggest major revision.

Comments for author File: Comments.pdf

Author Response

Please see the attachment 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors included most of my minor comments. I thank them for that. Some major comments were not addressed, due to the limited timeframe. I do understand that. However, the authors improved the discussion by stating the limits of their work.

I do not have further comment. I recommend accepting the paper.

Author Response

Thank you so much to Reviewer 2 for acknowledging our responses and understanding our situation with the limited time available for us to address all comments.  We are very grateful for his/her comments which helped us to refine the manuscript.  Our technical editor proofread the article for English grammar. I am glad to hear the reviewer does not have any further comments.

Buddhi