Progress in Developing Scale-Able Approaches to Field-Scale Water Accounting Based on Remote Sensing

Round 1

Reviewer 1 Report

The manuscript focuses on integrating data and models for estimating water use and conditions on the field scale. Various algorithms were compared in determining a series of hydrological variables. The results of two case-study sites in Australia made the point that multiple satellite and other data sources are available for driving the existing models for further applications at local scales. Overall, the manuscript is readable, but “water productivity” is not popular and confusing. In addition, the writing style could be more concise. Numerous places need double checks or cleanup.

 

Following are the places that caught my eyes.

 

The Title needs rewording. First, the current one is too general. Second, the phrase “at global locations” sounds confusing by mixing “global” and “locations”. This report focuses on “local” rather than “global”, and the word “locations” is unclear in terms of the field scale. Thus, it is more like: “Progress in modeling field-scale water use and conditions with multiple data sources”.

 

Line 28, the link does not work.

 

Line 31, clarify “this”, e.g., “this approach”.

 

Line 47, change to “arc-seconds”

 

Line 51, delete “have been” and “, however, this”.

 

Line 76, delete the subtitle.

 

Line 93 and 99, Figure 1 can be removed.

 

Line 102, double-check “However,”; the word sounds unnecessary.

 

Line 104, delete “are hydrological variables that”.

 

Line 131-133, delete these sentences. It is no need to repeat information “highlighted earlier”.

 

Line 134-136, the sentence is wordy. Delete “if”, “beyond …scales”; replace “tools which can be scaled” with “scaling”. Change “, there” to “. There”.

 

Line 162, separate the subtitle “2.1” into “2.1 Case Study Sites” and “2.2 Data Collection”. Modify the numbering of the following subsections.

 

Line 163-167, add more information about the sites, such as longitudes, latitudes, elevation, climate type, mean annual temperature, the range of annual precipitation, etc.

 

Line 208, add “of” between “results and “two”.

 

Line 216, no space before “where”. Apply to other places like this.

 

Line 273, how to calculate “Wuse”?

 

Line 357-364, the FAO’s ETr result is necessary background information. Thus, remove this subsection from the Results section.

 

Line 382, change “which is related to the” to “with”.

 

Line 555-556, delete the subtitle.

 

Separate the plots between Line 391-392 from the figure below (images). Otherwise, provide a detailed explanation in the figure caption.

 

Figure captions lack necessary detailed explanations for readers to understand the symbols, marks, scales that appeared in a figure. Figure Captions are supposed to be self-explainable, which means that readers can understand the figure without referring to the relevant text.

 

Double-check all equations.

 

Double-check the format of each reference, for example, formatting marks left on Line 679.

Author Response

Reviewer 1

The manuscript focuses on integrating data and models for estimating water use and conditions on the field scale. Various algorithms were compared in determining a series of hydrological variables. The results of two case-study sites in Australia made the point that multiple satellite and other data sources are available for driving the existing models for further applications at local scales. Overall, the manuscript is readable, but “water productivity” is not popular and confusing. In addition, the writing style could be more concise. Numerous places need double checks or cleanup.

Thank you for your comments, we have addressed the comments as well as possible. We have reviewed our writing and updated some of the style based on your suggestions. We have also removed “water productivity” from the title and used “crop water productivity” in the text where this relates to this area.

Following are the places that caught my eyes.

The Title needs rewording. First, the current one is too general. Second, the phrase “at global locations” sounds confusing by mixing “global” and “locations”. This report focuses on “local” rather than “global”, and the word “locations” is unclear in terms of the field scale. Thus, it is more like: “Progress in modeling field-scale water use and conditions with multiple data sources”.

We agree with the reviewer that the title needs rewording, but we want to capture the quantification of the water use and the remote sensing aspect of the approach and the scalability of the approach. The new title is: “Progress in developing scale-able approaches to field-scale water accounting based on remote sensing” 

Line 28, the link does not work.

 Checked both links in line 27 and 28 and they work

Line 31, clarify “this”, e.g., “this approach”.

 ‘This’ is clarified in the sentence: ‘this research area’

Line 47, change to “arc-seconds”

 accepted

Line 51, delete “have been” and “, however, this”.

Accepted, sentence now reads: “Finally, water footprints or crop productivity analysed at a single point using crop modelling [17, 18] do not easily scale to the larger catchment or country scale.

Line 76, delete the subtitle.

Agreed, the reason we originally added the subtitle was to highlight that the introduction covers two areas, the first part is a general overview of the problem while the second part is a specific review focussing on the remaining challenges (related to the discussion at the end in relation to scaling to global locations). As a result the introduction might seem long but we believe the content is important in relation to the overall story in the paper: outlining what the main remaining challenges are in this field and what progress has been made so far.

We agree that the subtitle was probably not necessary.

Line 93 and 99, Figure 1 can be removed.

 Accepted, figure no longer adds value to the paper

Line 102, double-check “However,”; the word sounds unnecessary.

 accepted

Line 104, delete “are hydrological variables that”.

 Accepted, sentence now reads: Evapotranspiration, precipitation, soil moisture, surface water levels, streamflow, water quality, and groundwater storage can generally be observed through remote sensing [32]

Line 131-133, delete these sentences. It is no need to repeat information “highlighted earlier”.

 Sentence rewritten to read now: More specifically the focus should be on the lack of accurate spatial ET estimates, lack of understanding of the fine scale spatial variation in inputs and outputs, and lack of understanding of on-farm storage of water [7].

Line 134-136, the sentence is wordy. Delete “if”, “beyond …scales”; replace “tools which can be scaled” with “scaling”. Change “, there” to “. There”.

Sentence changed to: In summary, three major remaining challenges remain if detailed water accounting and water productivity tools need to be developed that can be scaled from the field and farm to continent level

 

Line 162, separate the subtitle “2.1” into “2.1 Case Study Sites” and “2.2 Data Collection”. Modify the numbering of the following subsections.

 Accepted

Line 163-167, add more information about the sites, such as longitudes, latitudes, elevation, climate type, mean annual temperature, the range of annual precipitation, etc.

We are unable to give exact coordinates of the locations as this would result in privacy issues given the sensitivity of water data in Australia. However we have provided the approximate location and the size of the two clusters. We have also added additional information on elevation climate type, mean annual temperature and annual precipitation. “Study site a) is located at approximate coordinates 149.9° and -30.4° (WGS 1984) at a mean elevation of 226.9 m and covers an area of 1,032.57 ha. The site has a subtropical climate with no dry season, a mean annual rainfall of 629 mm, a mean temperature of 18.7°C, with a mean minimum temperature of 11.4°C and a mean maximum temperature of 26°C. Site b) is located nearby at approximate coordinates 150° and -30.5° at a mean elevation of 233.1 m and is 460.55 ha. The site has a similar climate, with a mean annual rainfall of 615 mm and, a mean annual temperature of 18.6°C, with a mean minimum of 11.3°C and a mean maximum of 25.9°C (http://www.bom.gov.au/climate/averages/maps.shtml).”

Line 208, add “of” between “results and “two”.

  Accepted

Line 216, no space before “where”. Apply to other places like this.

  Accepted

Line 273, how to calculate “Wuse”?

 This is defined in section 2.4. Sentence changed to: where Wuse refers to the water used in the field clusters (Section 2.4)

Line 357-364, the FAO’s ETr result is necessary background information. Thus, remove this subsection from the Results section.

 We politely disagree, as we state in section 2.3 that the ETr is “calculated from the climate data” and we provide the equation in the methods. As such this output is a “result”.

Line 382, change “which is related to the” to “with”.

 Sentence changed to: This clearly indicates the spatial variability of AET across the sites associated with different land cover (crops) and the irrigation scheduling.  

Line 555-556, delete the subtitle.

 We are uncertain why the reviewer would like to remove the subtitle. Instead we have inserted a new subtitle at the beginning of the discussion 4.1 General Discussion 

This is to clearly distinguish between the critical evaluation of the results (general discussion) and the forward looking/future research component (4.2)

Separate the plots between Line 391-392 from the figure below (images). Otherwise, provide a detailed explanation in the figure caption.

 Agreed, the caption was missing, figures renumbered and caption inserted

Figure captions lack necessary detailed explanations for readers to understand the symbols, marks, scales that appeared in a figure. Figure Captions are supposed to be self-explainable, which means that readers can understand the figure without referring to the relevant text.

 All captions reviewed

Double-check all equations.

 Done

Double-check the format of each reference, for example, formatting marks left on Line 679.

 

Done

Reviewer 2 Report

Excellent work, no remark from my side.

 

Author Response

Reviewer 2

Excellent work, no remark from my side.

Thank you for your encouragement

Reviewer 3 Report

This paper firstly showed progress towards an operational water cycle and then outline the challenges to extend this system to other places in the world.

I think that the paper is just a report not a paper. It can’t be acceptable for publication. The general comments are as follows:

 

1. In the abstract, there were no results and conclusions.
2. You just talked about how to do, but you don’t talk about what you have done.
3. The paper title is ‘at global locations’, however, you just talk two paddocks?
4. Insufficient details are given on the study area. What is the size of the two paddocks?
5. L164, The Namoi catchment is a large catchment. How large?
6. It need shorten Introduction. There are too many irrelevant statements about the objects.

Author Response

Reviewer 3

This paper firstly showed progress towards an operational water cycle and then outline the challenges to extend this system to other places in the world.

I think that the paper is just a report not a paper. It can’t be acceptable for publication. The general comments are as follows:

 

1. In the abstract, there were no results and conclusions.

Agreed, Abstract has been rewritten to include results and conclusions

1. You just talked about how to do, but you don’t talk about what you have done.

We politely disagree with the reviewer, there are extensive methods in the paper and we highlight novel research to use satellite data to quantify the field scale water use and demonstrate how this would be achievable down to fine scales, which can be scaled up to continental scales.

1. The paper title is ‘at global locations’, however, you just talk two paddocks?

We give examples of the application at two “clusters” (which are multiple paddocks). This is because we outline in the introduction that the definition of the water cycle at fine spatial scales is a major issue, rather than the application at continental scale. We then discuss what is needed to extend this type of work to global scales. However, taking into account your comment and the comments of reviewer 1, we have revised the title to better reflect the content.

1. Insufficient details are given on the study area. What is the size of the two paddocks?
2. L164, The Namoi catchment is a large catchment. How large?

Agreed, this was an omission. Size of the catchment has been inserted as well as more details on the case study sites (See comments with reviewer 1)

1. It need shorten Introduction. There are too many irrelevant statements about the objects.

The introduction covers two areas, the first part is a general overview of the problem while the second part is a specific review focussing on the remaining challenges (related to the discussion at the end in relation to scaling to global locations). As a result the introduction might seem long but we believe the content is important in relation to the overall story in the paper: what are the main remaining challenges and what progress have we made so far. We have reviewed the introduction and removed the Figure 1 based on the comments of reviewer 1 and have also shortened the text.

Round 2

Reviewer 3 Report

You said that there is a need for innovative algorithms and direct testing against observed data in line 68. What are your novel algorithms in your manuscript? You just used the ETLook ,CMRSET AET and other models.

How did you observer the soil moisture?

Overall this is only a report not a paper with innovation.

Author Response

Reviewer 3

You said that there is a need for innovative algorithms and direct testing against observed data in line 68. What are your novel algorithms in your manuscript? You just used the ETLook ,CMRSET AET and other models.

Reply: Thank you for your comment. The focus of this manuscript is to demonstrate that if we actually want to develop water footprint analyses at small (field to farm) scales we need to combine existing algorithms in a novel way and extend these with new algorithms. While we highlight that new novel algorithms need to be developed, we specifically show in this manuscript how combining some of the recently developed algorithms can be used to account for different water balance components at field to landscape scale using satellite data. To our knowledge there has been very little work to identify what is currently possible to fully account for water at the field and farm scale using satellites. As we point out, most of the work so far has taken place at much larger scales. This manuscript demonstrates the current tools and analyses the gaps in the tools to make satellite based water accounting at relatively small scales a reality 

How did you observer the soil moisture?

Reply: We clearly indicate that we don’t have observed soil moisture data in this case, we only present simulated data. We envision that in the future the simulations presented here will be linked stronger to satellite data (they now only use the satellite ET), for example through microwave soil moisture observations, or other work. As you rightly point out, without validation, all the satellite and simulation data is inferred data. However, we also indicate in the manuscript that this is one of the major gaps, which has also been identified by other authors. It is in fact a conundrum, without a demonstrated finer scale water accounting system it is difficult to convince farm operators or catchment managers to invest in on the ground monitoring to support the effort. This is exactly the kind of work we are attempting to achieve with the WaterSENSE project. In the discussion we highlight this point specifically: “The fourth major challenge is around validation data. A recent review by Massari et al. [12] highlighted that accurate determination of irrigated water use remains challenging. They particularly highlight the lack of validation data that is available to verify the predictions. But in the end, accurate predictions of water productivity are also in the interest of irrigators as water accounting can offer important clues for improving water use efficiency of irrigated systems.” 

We have now also added a sentence at the end of section 3.5 (“Soil Moisture estimation”): “Ideally, these results would be validated using observed soil moisture observations in the field, but these are currently not available.”

Overall this is only a report not a paper with innovation.

Reply: As we point out in our reply to your first comment, the innovation is not necessarily in the individual components that we present (and might seem like a report to you), but is in the integration of the components and gap analysis of the methods which provide water accounting from the field to the landscape scale. This is novel and has not yet been presented elsewhere.

Round 3

Reviewer 3 Report

Based on the revised version， I think it can be published.