Identification and Quantification of Actual Evapotranspiration Using Integrated Satellite Data for Sustainable Water Management in Dry Areas

Round 1

Reviewer 1 Report

·        The paper objectives are not clear. Are we only testing the efficacy of the RS model? If so, an assessment on based only one season is not enough. There are other models available. Authors have not done enough literature review to justify their work. Therefore, it needs to be explained why this work is needed.

·        The paper is lengthy. Section 3 includes lots of theories. This need to be shortened.

·        Line 359-363: accumulated ETo calculation period is November 25 to May 18, 2020. There seems some mistake in the defined period. Please check.

·        Line 268: Please mention that ET is ETactual (ETa).

·        The results of Figures 5,6, and 7 are obvious. ETo and ETa are different. What is the novelty of these figures?

·        Same is for Figure 8. This is normal behavior of Kc?

·        Figure 12: Although R2 is high, daily fluctuations in measured and RS estimated ET values are significant. Until February, RS measured values are significantly higher than measured ET values. In the later period, RS values were consistently lower than measured values. This needs a better explanation. Statistical parameters are indicative correction measures. However, we need to evaluate the behavior of the model on daily calculations of ET. Figure 12 shows that daily differences are significant (on some days even more than 1 mm/day). This questions the modeling approach.

·        I do not understand the need for including land use or cover map in this paper. It is obvious that water use in winter is lower than in summer as the ET values are changing. So, what do we want to get from this map?

·        The authors have concluded that remote sensing methods are still being assessed. They are only applicable if calibrated and validated accurately using ground data. The results achieved in this paper show that more work is needed to get a good calibration. Furthermore, these results are only for one wheat crop. Therefore, this model needs to be tested further on other crops (e.g. summer crops) before we recommend it for large-scale use.

·        Conclusions need to be more specific.

Author Response

Reviewer 1

Dear reviewer,

We appreciate your recommendations and modifications. Your suggestions have strengthened our paper. Thank you for your time and scientific assistance.

All the best

Authors

Response to comments:

1-         The paper is lengthy. Section 3 includes lots of theories. This need to be shortened.

Section 3. shows the fundamental equations of model calculations, including empirical equations and developed equation for modeling build up.

2-         Line 359-363: accumulated ETo calculation period is November 25 to May 18, 2020. There seems some mistake in the defined period. Please check.

The crop was wheat which cultivated on 25 Nov. 2020 and harvested on 18 May 2021 following the growing season growth period of spring wheat in Egypt.

3-         Line 268: Please mention that ET is ETactual (ETa).

Recent publication refer to actual evapotranspiration with only ET and that was used in whole manuscript but in line 268, we edited ET as per your request to be actual ET(in Yellow).

4-         The results of Figures 5,6, and 7 are obvious. ETo and ETa are different. What is the novelty of these figures?

Its mandatory and novelty to show figures of ETa and ETo for the following reasons:

-           Using energy balance flux towers aren’t wide in Egypt for measuring actual evapotranspiration in crops as per its high cost and its requirement of high level of data analysis and data quality control in addition to level of caring regarding sensors calibration, replacing malfunction sensors, removing dust continuously and regularly data checking in case any cutting of wires beneath the soil because of rats or machines sometimes.

-           It’s also mandatory to show both trends for new high yielding wheat variety in Egypt to determine actual consumptive use for best irrigation schedule in water scarcity crisis.

5-         Same is for Figure 8. This is normal behavior of Kc?

Crop coefficient (Kc) were developed in this research using field data measured using energy balance (EB) in middle of Egypt and calculated by dividing actual ET by reference ET

Kc= ETa/ETo

Kc calculation using FAO 56 was mainly in humid and semi humid area and Egypt now considered semi-arid area, therefore developing and upgrading Kc is also mandatory. Finally, evapotranspiration (ET) and crop coefficients (Kc) are needed to optimize the effectiveness and efficiency of irrigation practices/irrigation regime involving the application of water multiple times a day. How- ever, not much is known about the seasonal patterns and magnitudes in Kc values for wheat in Egypt.

6- Figure 12: Although R2 is high, daily fluctuations in measured and RS estimated ET values are significant. Until February, RS measured values are significantly higher than measured ET values. In the later period, RS values were consistently lower than measured values. This needs a better explanation. Statistical parameters are indicative correction measures. However, we need to evaluate the behavior of the model on daily calculations of ET. Figure 12 shows that daily differences are significant (on some days even more than 1 mm/day). This questions the modeling approach.

Because it is daily data, the variability is likely to be greater than on a weekly or monthly basis. The response of satellite observations is restricted to the pass time and the environmental conditions at the moment, while the EB station collects data at a very high frequency. Because EB stations are costly and need more work in upkeep and data processing, we must leverage the benefits of satellite data on a broad scale.

7-  I do not understand the need for including land use or cover map in this paper. It is obvious that water use in winter is lower than in summer as the ET values are changing. So, what do we want to get from this map?

Just to compare the water consumption (figure, 10) for every land cover/ use class (figure, 13).

8- The authors have concluded that remote sensing methods are still being assessed. They are only applicable if calibrated and validated accurately using ground data. The results achieved in this paper show that more work is needed to get a good calibration. Furthermore, these results are only for one wheat crop. Therefore, this model needs to be tested further on other crops (e.g. summer crops) before we recommend it for large-scale use.

The EB station was set in an open field farmed with wheat, and the station measured energy characteristics to be used in the EB equation without targeting wheat as a crop. So we utilized the EB data on a daily basis as ET data to verify the model and applied the model at a bigger scale, while the land cover/use map was used to interpret the larger ET map.

9- Conclusions need to be more specific.

Done

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors,

Please see the attachment

Comments for author File: Comments.pdf

Author Response

Reviewer 2

Dear reviewer,

We appreciate your recommendations and modifications. Your suggestions have strengthened our paper. Thank you for your time and scientific assistance.

All the best

Authors

Response to comments:

The following part had been added to manuscript

3.2.      Weather conditions and parameters during growing season

The minimum and maximum temperature, relative humidity (RH), solar radiation (Rs) and wind speed during winter season (2020-2021) as shown in Table (1) in Sids stations.

Table 1. The mean values of meteorological parameters at Sids station

3.2.         Experimental Design and Treatments

The experimental field size is 2.0 ha in Sids. Before planting in Sids site, the soil was plowed two perpendicular paths and laser leveled. Wheat cultivated on November 25, 2020, with seed rate (45kg/acre). The site was cultivated in raised bed with 130 cm width, 100 m length and 25 cm furrow depth with seven rows of wheat planted on the top of the beds with 15 cm apart using raised bed machine. The accumulated applied water was measured by water flowmeter at the field inlet.

A calibrated Energy Balance (EB) flux tower were installed in the experimental site in the first week of November 2020 to measure the actual evapotranspiration (ET).

Fertilization had been added as per agriculture research center (ARC) recommended doses; 75 nitrogen unit, 25 phosphorus unit and 20 potassium unit, Half of recommended nitrogen doses were added during 1st irrigation, and the rest was added with the 2nd irrigation event. Phosphorus and potassium fertilizers were totally added before planting with manual handed weeds control during the season

2- In the agricultural scientific community, analyzing only one year is very limiting. In fact, considering only one year, it is difficult to assess the environmental impact (temperature, rainfall and other climatic components). In view of this, I suggest that authors include in the title or abstract or in the method materials that the result of such an experiment is a preliminary results

Yes, it's only one season, but there's a lot of data there because the data is daily. We have measurements from the regular season that represent more than 70% of the same conditions in Egypt. Additionally, we did not forecast the yield or any other crop characteristics; rather, we simply assessed the RS model by observing how the crop interacted with the environment under typical conditions. The second or third season might represent the same conditions when the extreme seasons happen once or twice every ten years. In Egypt and arid zones, irrigation practices are the most significant factor in crop water consumption under normal circumstances—not rainfall—as is the fact that the country's agriculture system is irrigated.

reference have been added, Irmak et al, they used simplified energy balance (Bowen ratio) for their research (highlighted in yellow in review and reference).

4- please report the number of installations

Two solar-powered flux towers were installed at the experimental site with appropriate sensors to measure various components of the surface EB and agro-metrological climate parameters for reference evapotranspiration measurements (ETo).

edited line 193

6- Can a reader understand those abbreviations without the name of each? Please enter what each abbreviation means for each section, it is difficult for a reader to remember each abbreviation

All abbreviations are described at least once in the first mention.

Done

Done

Done

Actually, we detected the best parameters based on our long experience in this work.

Random forest is a supervised learning algorithm. The "forest" it builds is an ensemble of decision trees, usually trained with the “bagging” method. The general idea of the bagging method is that a combination of learning models increases the overall result.

A resampling technique called cross-validation is used to assess machine learning models on a small data sample. The procedure has a single parameter, k, that designates how many groups should be created from a given data sample. As a result, the process is frequently referred to as k-fold cross-validation. When a particular value for k is selected, it may be substituted for k in the model's reference, such as when k=10 is used to refer to cross-validation by a 10-fold factor.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I still believe Figure 7 may be deleted because it did not provide any extra information.

Reference are not in format. Lot of references are very old. May be repaced with some latest work. 

Please check spelling mistakes.

Author Response

First, we would like to thank you for your comments and suggestions. Your modifications are appreciated.

Secondly, please find attached responses to your comments and suggestions.

Comment 1: I still believe Figure 7 may be deleted because it did not provide any extra information.

Response 1: Done. We removed figure (7) and renumbered the rest of the figures.

Comment 2: References are not in format. A lot of references are very old. Maybe replaced with some latest work. 

Response 2: we formatted all references as journal queries and added some new references. Note: more than 40% of references have been published in the last five years.

Comment 3: Please check spelling mistakes.

Response 3: Done, all modifications are colored yellow.

Reviewer 2 Report

Dear Authors,

From my point of view, "accepted".

Author Response

Thank you, we appreciate your efforts in reviewing the manuscript to strengthen the content before publishing.