Effects of Increasing C4-Crop Cover and Stomatal Conductance on Evapotranspiration: Simulations for a Lake Erie Watershed

Round 1

Reviewer 1 Report

The manuscript presents a study based on a process-based model to examine the influence of c4-crop cover and stomatal conductance on ET at watershed level. The topic is of interest to the journal. In general, the study is clear, and easy to follow. My major concerns on the study include,

• The accuracy of LAI estimation is unknown although the estimates were compared to that in the literature. The empirical LAI algorithms based on vegetation index may be affected by crop type, phenology and spaces. Re-parametrizing the vegetation index based models using field measurements is required.    
• A calibrated BEPS model is needed before performing the scenarios. The current analysis for the three different stomatal conductance may truly indicate that the BEPS model requires model parametrization based on field measurements, such as GPP, crop biomass and ET.
• Daily LAI is required by the BEPS model. However, LAI interpolation based on the limited 8 satellite estimates to obtain daily LAI may be difficult.

Author Response

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Reviewer 2 Report

In this study, the authors investigated the sensitivity of ET to land cover change and stomatal conductance. It is a very interesting study and the manuscript is well written.  I partially like the way the authors describe their methods and data source, super clear! I enjoy reading this manuscript and the findings and conclusions are solid.  I believe this study will add knowledge to the research community of hydrology and agriculture. 

Line 193-194.  Could you elaborate more on the method of resampling/downscaling the data to 30m resolution? 

Line 282.  What is "SR"?

Table 2.  Please add the reference for the algorithms. 

Table 3.  Row 1, "GSimple Ratio"?  Row 4.  What is "L"? 

Line 326.  Is there a public repo for the code you developed? 

Line 476-477.  It might be worth mentioning that the optimal growth temperature varied based on the growth stages.

Author Response

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Reviewer 3 Report

This paper is a good case study on the influence of crop-specific-stomatal conductance and crop cover (corn cover) on ET rates. Given that much of the analysis is derived from previous studies, can the authors provide clear statements of what is  novel here or what describe at least how this exercise has not been found anywhere else?  Perhaps the integration of these previously derive formulae and indicating the need for further research on suitable formulae but this should really be brought to the fore-front; because as it stands, it is really a case study or technical note. 

As well, could the authors provide greater discussion of how their choices, assumptions and inherent errors lead to their results? For example, the paper results indicated that increasing corn coverage in the study area did not significantly increase ET in July or August. However, changing the stomatal conductance of the crop will change the ET rate to a large extent so how much is related to stomatal conductance vs other variables? In addition, perhaps the authors could discuss the data limitations in this research. For example, in line 235, the C4 photosynthetic of sorghum may not be the same as corn, so I suggest discussing input error in the discussion section.

ECOSTRESS ET product is the crucial verification part of the BESP result. To what extent can the ECOSTRESS ET product reflect that your BESP ET results are credible if the data of the ECOSTRESS ET product is limited? (Line 347)

With regard to the data analysis, if hourly BEPS can obtain more accurate results, why is daily data still used in the BEPS? Can you discuss how different time scales influence your analyses?

There are just a few minor changes to consider;

line 40	Need references to support your argument
line 69	Please add a semicolon before while
line 149	Full name of USDA is required on the first mention
all figures	Can the resolutions of the figures be improved?
line 175	Please indicate that this is a radar image. It is recommended to add a boundary for the area of your research interest. For example: highlight your study area in the bottom left image or add a highlight border to distinguish the rest of the area.
line 176	Figure Caption error, 'Figure 1.' should be bold
line 209	Table format (only need bold for 1st line, also the caption 'Table 1.' need bold)
line 183	What is the meaning of Eeflux?
line 255, 256	Grammar error, missing period
line 290	It may be necessary to move the second sentence to Table 3
line 348	It is recommended to change the color display of the boundary, and the usage of red color is not clear. From the observation, the contour is different from the study area of figure 1.
line 429	Figure 10 is far away from your first mention
line 491	Table data missing
line 549	Extra white space; need to move image above, an editing error
line 591	The table is formatted incorrectly

 

Author Response

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Round 2

Reviewer 1 Report

I do not have further comments. 

Author Response

Thank you for your time and comments