Abstract
Understanding how different crops use water over time is essential for planning and managing water allocation, water rights, and agricultural production. The main objective of this paper is to characterize the spatiotemporal dynamics of crop water use in the Central Valley of California using Landsat-based annual actual evapotranspiration (ETa) from 2008 to 2018 derived from the Operational Simplified Surface Energy Balance (SSEBop) model. Crop water use for 10 crops is characterized at multiple scales. The Mann–Kendall trend analysis revealed a significant increase in area cultivated with almonds and their water use, with an annual rate of change of 16,327 ha in area and 13,488 ha-m in water use. Conversely, alfalfa showed a significant decline with 12,429 ha in area and 13,901 ha-m in water use per year during the same period. A pixel-based Mann–Kendall trend analysis showed the changing crop type and water use at the level of individual fields for all of Kern County in the Central Valley. This study demonstrates the useful application of historical Landsat ET to produce relevant water management information. Similar studies can be conducted at regional and global scales to understand and quantify the relationships between land cover change and its impact on water use.
Highlights
The Central Valley of California is one of the most productive agricultural regions of the United States with more than 250 different crop types and an agricultural sector that accounts for 77% of the state’s water use [1]
Because we considered only “active crop parcels”, the Kern County crop parcels were filtered in each year for parcels that averaged ≥ 0.5 in May–September maximum Normalized Difference Vegetation Index (NDVI), and so, only these parcels were included for further analysis
Using the average production of shelled almonds per unit of area from the USDA-NASS 2012 Census of Agriculture and the volume of water measured by this study, we found that the ratio of water per almond nut to average closer to 3.56 L (0.94 gallon) per almond—SSEBop water use falls within 15% below the commonly reported metric [39]
Summary
The Central Valley of California is one of the most productive agricultural regions of the United States with more than 250 different crop types and an agricultural sector that accounts for 77% of the state’s water use [1]. Due to advances in thermal remote sensing ET modeling and cloud-based processing, actual evapotranspiration (ETa), from a moderate-resolution satellite such as Landsat, can be used to estimate patterns in water use over large areas like the Central Valley more efficiently. Et al [5] modeled historical ETa for 31 years of Landsat data over several hydrologic sub-basins in the middle and lower Central Valley and demonstrated the reliability in estimating water use over time with remote sensing. This study is the first of its kind to model 30-m resolution actual evapotranspiration from thermal remote sensing for the entire Central Valley to estimate crop water use in irrigated agriculture for the period 2008–2018
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
