Evaluating the adaptability of an irrigation district to seasonal water availability using a decade of remotely sensed evapotranspiration estimates

Abstract

Competition for fresh water is increasing in highly populated areas especially those regions located in arid and semi-arid climates. Water uses are under scrutiny to determine the potential for water savings. Particularly, the agricultural sector is identified because it is the largest consumer of water. However, information is limited on the year-to-year variability of agricultural irrigation management, specifically the variability related to seasonal water availability. Remote sensing is a useful input into models to estimate actual evapotranspiration (ETa) for large irrigation districts and provides an archive of historical data. In this paper, a decade of remote sensing data are used applying the METRIC algorithm and linear interpolation to achieve ETa estimates. Inter-annual variations in seasonal ETa are related to snowpack, weather, irrigation diversions and crop data to understand the factors having an impact. It was found that consecutive (second) years of dry or wet events impacted the seasonal ETa, indicating limitations in the buffer capacity of the irrigation district. This study shows that the irrigation district is capable of buffering dry or wet events during the first year, but need to adapt during a consecutive year of extreme dry or wet weather. Additionally, cropping patterns indicate that the crop choices in the irrigation district do not change during extreme events. In contrast, irrigation diversions are influenced by prolonged dry events. The depleted fraction indicated good performance of the irrigation system, with potential for improvements in dry years. This study demonstrates the dynamic consumptive water use of an irrigation district, thereby indicating the importance for considering multiple years of data for an assessment of the agricultural sectors’ water use. Additionally, the impact of seasonal water availability gives insight on the adaptability of an irrigation district and its’ capability to cope with current and future variability in weather conditions and extreme events.