Spatial and Temporal Analysis of Water Resources in the Olive-Growing Areas of Extremadura, Southwestern Spain

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper unveiled the spatiotemporal changes in water resources due to climate change in the olive-growing regions and its potential effects on olive growth. Overall, it is well-written and provides readers with a clearer picture, but it lacks several details regarding the results and discussion.

1.       What’s the principle for selecting the climatic indices? Are they commonly used in the water resources assessment?

2.       Add the latest literature reviews about the water requirements of crops and water resources assessment in the introduction.

3.       Changes in water resources are induced by many drivers, such as climate change, land use, agriculture and urbanization. In this paper, the authors did not consider land use or cover, as it is a major factor in dominating the water resource changes.

4.       Due to the lack of detailed information provided by the authors regarding anthropogenic activities in this area, it is difficult to differentiate between the impact factors of climate change and human activities in spatio-temporal water resources.

5.       Why the olive areas in Figure 1 and Figure 2 are different?

 

6.       Extend the analysis of the spatial and temporal trends in water resources. What induced this trend? 

Author Response

1. What’s the principle for selecting the climatic indices? Are they commonly used in the water resources assessment?

This article aims to conduct a spatial and temporal analysis of water resources associated with olive cultivation in Extremadura. The majority of this crop is grown under dry farming conditions, meaning without water inputs from reservoirs or wells. Under these conditions, the primary climatic variables that most significantly affect the crop are effective precipitation (natural water resource) and temperature. Secondly, the aridity index, which integrates the previous two variables, and finally, the crop evapotranspiration (ETC), which analyses the specific water requirements of olive cultivation. Once the water requirements and effective precipitation are known, we can assess the scarcity or abundance of resources for olive cultivation by comparing the difference between them.

From an agronomic perspective, these variables are the most influential on crop yields and, therefore, from our point of view, the most suitable ones to consider.

 

2. Add the latest literature reviews about the water requirements of crops and water resources assessment in the introduction.

 

More information and new references have been included in the introduction.

 

3. Changes in water resources are induced by many drivers, such as climate change, land use, agriculture and urbanization. In this paper, the authors did not consider land use or cover, as it is a major factor in dominating the water resource changes.

 

This article addresses, from an agronomic perspective, the spatial distribution and temporal analysis of water resources from rainfall and the evapotranspiration of olive cultivation in Extremadura. The goal is to understand the differences within the territory and to adopt better water use efficiency measures in response to climate change.

 

4. Due to the lack of detailed information provided by the authors regarding anthropogenic activities in this area, it is difficult to differentiate between the impact factors of climate change and human activities in spatio-temporal water resources.

 

The water resources we have analysed are solely those derived from rainfall, which is the only source for the majority of the cultivated area. For this reason, we have indicated on the maps the areas where olive plantations are currently located in Extremadura.

 

5. Why the olive areas in Figure 1 and Figure 2 are different?

 

Figure 1 has been corrected.

 

6. Extend the analysis of the spatial and temporal trends in water resources. What induced this trend?

 

An additional paragraph and new references have been included.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, overall I think your paper is very good and contributes well to your topic. The language flows very fluently. Here are some suggestions for you to consider that I think might enhance the paper that much more.

1. In terms of irrigation that you referenced in your paper: have you considered the different types of irrigation methods in use around the world today and which of them, if any, would provide a viable alternative in alleviating the drought problem with the olive trees?

Some references to provide you some ideas are: (a) Economic performance of irrigation capacity development to adapt to climate in the American Southwest; by Frank A. Ward, Terry L. Crawford, in the Journal of Hydrology, http://dx.doi.org/10.1016/j.hydrol.2016.06.057.

(b) Economic feasibility of developing alternative water supplies for agricultural irrigation; Edirisooriya Mudiyanselage et al., (2023), https://doi.org/10.1016/j.coche.2023.100987.

(c) Impact of alternative water policies for drought adaption in the Guadalquivir Mediterranean river basin, southern Spain; Javier Martinez-Dalmau et al., (2023), https:// doi.org/10.1016/j.ejrh.2023.101444.

(d) A Decade of Irrigation Water use trends in Southwestern USA: The Role of Irrigation Technology, Best Management Practices, and Outreach Education Programs, by Issac K. Mpanga, Omololu John Idowu, in Agricultural Water Management, https://doi.org/1016/j.agwat.2020.106438.

(e) Understanding grower perceptions and attitudes on the use of nontraditional water sources, including reclaimed or recycled water, in the semi-arid Southwest United States, by Jessica L. Dery et al., in Environmental Research, https://doi.org/10.1016/j.envres.2018.12.039.

2. Since excessive irrigation can deplete both surface and groundwater supplies, I think it might help if you can describe which river basins, in terms of surface water and groundwater, are affected from evapotranspiration from the olive trees and would changing irrigation techniques help to maintain adequate water supplies for the olive tree industry? 

Author Response

1. In terms of irrigation that you referenced in your paper: have you considered the different types of irrigation methods in use around the world today and which of them, if any, would provide a viable alternative in alleviating the drought problem with the olive trees?

 

In this research the main objective is to determine the spatial distribution of climate variables related to water resources in the olive-growing areas throughout Extremadura.

The water requirements of the crop have been analysed, and based on that information, the irrigation system would be studied for each case. Thus, depending on the efficiency of the system and the quality of the water and soil, the irrigation dosage would need to be adjusted accordingly.

 

2. Since excessive irrigation can deplete both surface and groundwater supplies, I think it might help if you can describe which river basins, in terms of surface water and groundwater, are affected from evapotranspiration from the olive trees and would changing irrigation techniques help to maintain adequate water supplies for the olive tree industry?

 

In this study, we did not aim to cover water resources other than precipitation. The objective is to identify the areas that are most suitable for olive cultivation from a climatic perspective, focusing on water requirements and the balance with precipitation. Based on this work, future studies could evaluate the efficiency of different areas in utilizing other water resources (such as reservoir water) and select the most efficient zones for their use from a climatic standpoint.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript presents an interesting study and analysis of water resources over space and time in the olive-growing regions of Extremadura, Southwestern Spain. To further enhance the manuscript, the following comments and suggestions need to be addressed by the authors: 

- Equation 1, line 163, represents a standard Hargreaves equation for calculating PET, not PET for olive cultivation as stated in line 161. Please revise this. To calculate the evapotranspiration of olive crops, the crop coefficients for olives should be incorporated. 

- In line 208, you stated that the resolution is 1000 x 1000. I assume the units are in meters. 

- In Section 3.1, you stated that PET data come from a normal distribution and that the AWR and If come from a lognormal distribution. Why is this important? Did you fit those data to those distributions? If so, you did not present the results regarding this. 

- In Figure 2, do these maps represent yearly average values? Please be more specific in the figure title.

 

- You have analyzed standard meteorological indices PET, AWR, and I_f, which can be related to any crops, not exclusively to olives. This means that the results of your study could impact other crops in the research area, not just olives. Have you considered using more specific parameters/indices related to olives, such as ETc for olives or net irrigation requirements for olives, etc.?

Author Response

- Equation 1, line 163, represents a standard Hargreaves equation for calculating PET, not PET for olive cultivation as stated in line 161. Please revise this. To calculate the evapotranspiration of olive crops, the crop coefficients for olives should be incorporated.

 

The text has been modified to better explain how the PET for olive cultivation was computed.

 

- In line 208, you stated that the resolution is 1000 x 1000. I assume the units are in meters.

 

The units (m) have been included.

 

- In Section 3.1, you stated that PET data come from a normal distribution and that the AWR and If come from a lognormal distribution. Why is this important? Did you fit those data to those distributions? If so, you did not present the results regarding this.

 

The fact that the data follow a normal or log-normal distribution is positive for the subsequent geostatistical interpolation process, although it is not an essential requirement. A statistical test could be conducted to confirm this, but it is not necessary. In this case, the mean and median values, as well as the skewness coefficient, have been compared to estimate the data distribution.

 

- In Figure 2, do these maps represent yearly average values? Please be more specific in the figure title.

 

The figure title has been modified.

 

- You have analyzed standard meteorological indices PET, AWR, and If, which can be related to any crops, not exclusively to olives. This means that the results of your study could impact other crops in the research area, not just olives. Have you considered using more specific parameters/indices related to olives, such as ETc for olives or net irrigation requirements for olives, etc.?

 

Although the methodology of the study can be applied to any crop, in this case, specific indices for olive cultivation have been used. The evapotranspiration was computed for olive trees, and, consequently, the determined water requirements are also specific to this crop.

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors answered my questions, and the paper has been improved. It can be accepted.