Extended Dependence of the Hydrological Regime on the Land Cover Change in the Three-North Region of China: An Evaluation under Future Climate Conditions

Round 1

Reviewer 1 Report

All my syggestions are in the PDF form of the paper. There are a lot of comments that may help you to improve the paper. 

I would like to precise that the paper is more suitable to ”Water” Journal from MDPI  or at a specific journal about hydrology issues. 

Comments for author File: Comments.pdf

Author Response

Thanks for all your suggestions. All my responses are included in the Word file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments:

The manuscript presents a case study of examining the impact of using two past land use/cover (LUC) maps on predicting future evapotranspiration, runoff, and soil moisture based on the Variable Infiltration Capacity (VIC) model and future climate data. The English writing is good in general and the topic should be of interest especially in the study area of China. However, since any hydrologic model including the VIC must consider LCC and vegetation which both can change over time, particularly in a study area such as China, it’s logical to use future LUC and vegetation data to predict future changes. Yet this study mainly used two past, but not future, LCC and vegetation data and made predictions separately, which I view it as the greatest weakness in its methodology. I understand the study considered climate change and LUC as two independent factors, just as what’s been briefly described in the last limitation in# 4.2. However, Shouldn’t this assumption be presented at the beginning as it lays the critical theory foundation of the research? With this, I also feel more discussion about this topic should be presented in #4.2 since its way more important than other limitations being presented in the current paper. Overall, many areas in the manuscript require further clarification if it can be accepted for publication, which are indicated below:

1.      Abstract: should include some results regarding the “dependence of the future hydrological regime on past LCC”, since this is the research goal.

2.      Introduction:

1)      Should include some information about the major types of hydrological models being used in similar research, e.g., names, major rationale/characteristics of each model type, etc.

2)      I feel the study goal/objectives is not clearly presented

3)      Should include some sentences about research significance in the end

3.      Study area:

1)      should have some information about total population

2)      It will be great if the dominant climate pattern, such as arid or semi-arid, in each of the five large river basins or the whole study site is also presented

3)      What is the reference for the 2015 LUC map?

4.      Hydrological model

1)      #113-116: the sentence reads a bit awkward and should be re-phrased

2)      more background information about the VIC should be given, e.g., its basic principle, major characteristics, who it has been used in the past, since they are not presented in Introduction

3)      I feel the information will flow better if #2.2 and 2.3.2 are presented together  

4)      #124: some background information about ISI-MIP should be given

5)      #124: why “new” bias-correction model is needed for ISI-MIP?

6)      #128: why only five GCMs and only these five GCMs were considered?

7)      #141-142: what classes in the LUC maps were used as the “vegetation parameters”?

8)      The current research seemed to use data/results from references 28 and 24 quite a lot, so authors should provide some background information about the two references. Besides, for the LUC maps, information such as class types, methods for their extraction, and accuracy level should be given.

9)      a link for the LAI data should be provided if available

10)   I don’t understand why the first experiment didn’t start with the older LC 1986 data.

11)   #171-172: why are four periods beginning in 2020 and not, for example, 2030? Also why each of the four periods is 19-yr apart?

5.      Results:

1)      Is #3.1 already presented in reference 28? Or results from this section were figured out by the current authors?

2)      #3.2 and 3.3: why these two sections only presented results for 2020-2039 and 2080-2099? What about other periods? Besides, authors should present the results of each of the two periods before comparing their results.

3)      #3.3: why only the results based on the LC2015 data were presented? Besides, authors should discuss about methodologically speaking, what will be the implication of using two different LUC maps in such kind of research.

4)      #278: “based on the two simulation…” ->only results from one experiment were provided.

5)      #3.4: authors should present some results by comparing each of the four time periods.

6.      Discussion:

1)      #326-333: authors should give a time frame regarding these LUC changes being presented.

2)      #348: what does “A1B” stand for?

7.      Figures:

1)      Fig 3, 5, and 7 are hard to read based on the current map scale. Authors should also consider labeling each major river basins in these figures as it will help readers to interpret results given in the text way better.

2)      Fig 9: what does IR, HR, YR, etc. mean?

Author Response

Thanks for all your suggestions. All my responses are in the Word file.

Author Response File: Author Response.pdf

Reviewer 3 Report

This research focuses on the simulation of the future hydrological regime (2020-2099) which should characterize the Three-North region of China as a result of recent land cover changes and in a climate change scenario.  The general  problem the authors want to address is interesting but I have some doubts about significance of results and conclusions.

To the best of my knowledge, the Three-North Forest Shelterbelt program is still in progress and further LCCs are expected in the area until its end in 2050. More in general, the real future hydrological regime might highly diverge from that predicted in this paper due to changed  land cover conditions after 2015 (reference year). Thus, to avoid confusion, the work results should not be discussed as actual “forecasts” (e.g., see the conclusive part : <<the hydrological regime will experience…>>) but only as the simulated response to "specific LCCs". What will occur in the future is another question.

In addition, the authors do not provide any argument to convince the reader of the confidence of their simulations. Magnitude of  the predicted temperature trend in the area is impressive (figure 4). As this is a mean value, I expect that in some areas the increase is even higher thereby depicting a catastrophic scenario. Thus, I wonder whether the initial lvegetation cover might really survive in these changed conditions, as it strictly depends on climate. In other words, climate projections could be inconsistent with the author hypothesis of a constant land cover thereby inducing doubts about the reliability of the simulation as a whole. In my opinion this point should be carefully discussed to explain why instead the proposed simulation is good.

Author Response

Thanks for all your suggestions. All my responses are in the Word file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors made a great job with the corrections. 

However, there are some issues to be clarified:

Please, put the paper on the journal requirements format (download from the journal site). 

Please, add the author contributions (these are included in the manuscript you will download.

Reviewer 3 Report

The revised paper better puts into evidence extent and limitation of the research. In the present form, the risk of misunderstanding appears to be mostly avoided. I do not know if there is a problem in the pdf file or the paper is really not formatted. Please check the correctness of the format, as I noticed some problems also in the version without revisions.