Remote Sensing and Modelling Based Framework for Valuing Irrigation System Efficiency and Steering Indicators of Consumptive Water Use in an Irrigated Region

Round 1

Reviewer 1 Report

The article is devoted to the spatial estimation of consumptive water use for performance assessment of the Indus Basin Irrigation System of Pakistan using Remote Sensing. It is a meticulous analysis, interesting and of course useful to the authorities in the analyzed area. The undertaken study can be applied to any other irrigation system to manage water wisely and sustainably. The paper is very well written and I propose to be published in its present form.

Author Response

We are thankful to the respective reviewer for very encouraging remarks and acceptance of the paper without any further changes. 

Reviewer 2 Report

This study aims to present an approach to determine consumptive water uses based on a Remote Sensing approach for water resources planning, management, and regulations. The assessment includes data collected at field level and estimations based on remote sensed data. The results of the present study indicate that remote sensing can successfully  overcame the constraints from field-based approach, allowing to capture the field-scale heterogeneity with a high temporal coverage.

The paper is well-structed, allowing the reader to have an overview of the methodology adopted. However, and despite of the presented results, I will regretfully have to reject this MS because it does lack the fundamental of a valid calibration and validation of the proposed methodology. I need to underline that, for a study are of more than 2.3 Mha, evapotranspiration data, the essential variable for estimate consumptive water use, is only validated by using data from only one weather station. The authors try to overcome this lack of information adding two more rainfall information sites (located outside the study area); again, one can argue that this is not enough for such a wide study area. Thus, a better calibration/validation of remote sensed data is advised.

The authors should be able to re-write the work by following these outlines:

Introduction

The review is insufficient and lacks information of past studies available in literature. There are several studies that adopt similar approaches.

Datasets

3.3. Field data: Authors state that field data collection campaigns were conducted in during three different seasons at two different locations; again, for an irrigation are of more than 2 Mha one can agree that this is not enough to validate the data estimated by the model. If more data were collected, the authors failed to prove so.

Methods

This section could be more summarized, referring the method to the original papers; or, if the authors consider their presentation essential, the control variables should be presented in a more summarized form.

Results

The modelled results need to be compared with field data in order to prove their quality. I don’t quite see that in this section.

 

Concluding, this MS should be rejected in its present form. It requires among other issues a more robust review, a better validation of the adopted approach, a more appropriate description of the collected data and an improved validation of the modelled results.

Author Response

The reply can be found in the attached file. 

Author Response File: Author Response.docx

Reviewer 3 Report

This paper addresses an approach to determine spatio-temporal consumptive water uses using Remote Sensing data and modelling approaches in a data-scarce irrigated agricultural region located in Pakistan. The study makes use of both remote sensing and point data (secondary information) for addressing the issues of irrigation efficiency and indicators that influence consumptive water use patterns. Overall the paper is well structured and written. The results are based on a wide spectrum of data and analyses. However, I feel that the length of the paper could be reduced at certain parts for better readability. I suggest the following changes before the possible publication of this paper.

• Methods: The methodology of SEBAL is not necessary to write in detail as it has already been published in many papers, so only reference to some basic publications along with a work-flow diagram adopted for the current study is enough.
• The authors used meteorological data from three stations in/ near Rechna Doab. Could they justify if that data from those sparsely located stations could be well represented and useful to be utilized specially for the validation purpose?
• The results of land use land cover mapping are presented in very detail that is not necessary as it is not a core objective of the paper and therefore can be shortened including figure.
• The section “5.6.4 Importance assessment by overall consumptive water use” presents detailed results that are also shown in Figure 16. Figure 16 is very complex and does not add much value to the contents of the paper, the should be improved if authors wants to retain it other than that only a descriptive text can also serve the purpose. This could improve the structure of the manuscript without affecting important information.

In conclusion, I see that the results of this study are worth to be published after addressing the above points as it adds further knowledge to water resources management and to understand their patterns of usage.  

Author Response

The authors are thankful for the encouraging comments raised by the reviewer. The reply to minor changes recommended by the reviewer can be found below:

1. In the formatted version of the manuscript, the detailed methodology of SEBAL is omitted and only the basic references and flow of work are retained.  
2. We appreciate the reviewer for raising a very important question on the usage of meteorological data in the vicinity of the study region. We adopted the current methodology because of two reasons, (a) the Thiessen polygon approach was utilized that is a standard method to cater to the variability of rainfall data from the point locations (b) the autocorrelation for precipitation data at these locations were studied by Usman et al. (2020) and their results justify our methodology.
3. The results of land use land cover mapping are shortened in the formatted manuscript and only very important results are presented as recommended.  
4. Figure 16 is omitted from the formatted version of the paper as recommended and results are only described as a text. The remaining figures are numbered accordingly.   

Reference: Usman, M., Qamar, U. M., Becker, R., Zaman, M., Conrad, C., Salim, S. (2020) Numerical modeling and remote sensing-based approaches for investigating groundwater dynamics under changing land-use and climate in the agricultural region of Pakistan. https://doi.org/10.1016/j.jhydrol.2019.124408

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors tried to rewrite the MS, adding some references from previous studies, improving the state-of-the-art. Also, they reduced the “Methods” section, easing its readability.

In spite of their efforts, and despite of their claim that previous authors used no field data to validate their approaches, I maintain the opinion that, for such a wide study area, valid calibration and validation of the proposed methodology must be assured.

Thus, this MS should be rejected in its present form since it still requires an improved validation of the modeled results to prove the model capability to provide for reliable simulations.

Author Response

Thank you very much for your recommendations and for the review of our paper.