What Drives Crop Land Use Change during Multi-Year Droughts in California’s Central Valley? Prices or Concern for Water?

Round 1

Reviewer 1 Report

General comments:

The manuscript used existing multi-source data sets to examine the cropping pattern changes, their responses to crop prices and water pumping cost, and their impacts on water use and groundwater level in California’s Central Valley between 2007 and 2016. All the data are not produced by the authors themselves, and the research methods and topics are not novel and have nothing to do with remote sensing. Thus, this paper is out of the scope of Remote Sensing, and needs thorough revision to meet the publication requirements of other related Journals, e.g., Water, Sustainability.

Specific comments:

1. The current introduction is chaotic. The authors need to deeply review more previous research to clarify knowledge gaps and to highlight the importance of your study.
2. In the 2.1 subsection, the authors should add a basic description of the cropping pattern, crop water use, and other climate conditions (e.g., multi-year average temperature and dryness index) in the study area. The data source and period of long-term rainfall should be clarified. The elevation and rainfall gradients can be better showed using a classified symbology in Figure 2.
3. The relevant information of multiple data source can be explained more clearly in a self-explanatory table. The 2.3 subsection must be rewritten.
4. The spatial distributions of 30 m resolution cropping pattern and crop water use need to add in the results to clearly show the heterogeneity of pattern and its changes. The authors should make more efforts in the results section to increase the credibility. E.g., the reduced pasture area in the Figure 3 can be show in a loss and gain maps of cropland to prove that it changed to cropland, but the current form cannot explain.
5. The authors should add a new section (i.e., discussion) to clarify the other reasons and impacts of cropping pattern changes, the comparison with related research, and the advantages, disadvantages and future research topics of this study. All the explanations in results and conclusions should be moved to the discussion section.
6. The title of “5. Summary and Conclusions” should be changed to “Conclusions”, and this section must be rewritten. All the explanations and discussion should be moved to the discussion section, and all the description of background and methodology should be shortened. The authors should avoid the repeat of results and only keep the most important findings.
7. The language needs revision.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This is a very interesting paper on a very significant agricultural region.  I last visted the SJ valley about 20 years ago, and your paper shows the staggering amount of change in the crop mix.

I think the paper could do with a little more mention of the urban / envoronmental demand for water and its impact on water price/use.  These could be either in the discussion or introduction. Does this vary between counties?

Has salinity played a role in the crop mix in any specific county's.  It used to be a major problem in some ?

 

In table 1 could you add a column with the $ return per megalitre (or acre feet).  ie the return per unit of water used ?

Abstract

line 19 is that water price, crop price ??? clarify.

page 13 423: reference 50 states 75% loss of cotton ? did they say why?  that might enhance your discusssion in that paragraph.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This was a well-written paper, easy to read and understand, as well as a very interesting study with significant policy implications.  I recommend publication. 

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Most of my comments have been well responded or revised. Some revisions should be made before publication.

1. The spatial distribution of multi-year average drought indicator should be added in Figure 2. Why the authors used the outdated (1970-2000) instead of the latest (WorldClim 2.1, 1960-2018) precipitation data in Figure 2? The data currently used cannot reflect the precipitation distribution during the study period (2007-2016).
2. Although this study just focuses on the analyses at Central Valley and county levels, the spatial distribution of cropping pattern and crop water use and their changes can provide valuable information for readers, and these maps of the starting and ending years and their changes are easy to add.

Author Response

Please see attached.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

All my comments have been well addressed. The paper can be accepted in present form.