Abstract
Evapotranspiration (ET) is one of the biggest data gaps in water management due to limited ET measurements, and further, spatial variability in ET is difficult to capture. Satellite-based ET estimation has great potential for water resources planning as it allows estimation of agricultural water use at field, landscape, and watershed scales. However, uncertainties with satellite data derived ET are a major concern. This study evaluates hourly satellite-based ET from 2001–2010 for the growing season (May–October) under irrigated and dryland conditions for both tall and short crops. The evaluation was conducted using observed ET from four large weighing lysimeters at the United States Department of Agriculture Agricultural Research Service (USDA-ARS) Conservation and Production Research Laboratory in Bushland, Texas. Hourly ET from satellite data were derived using the Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC) model. Performance statistics showed that satellite-based hourly estimates compared to lysimeter measurements provided good performance with an root-mean-square error(RMSE) of 0.14 mm, Nash–Sutcliffe efficiency (NSE) of 0.57, and R2 of 0.62 for ET for dryland crops, and RMSE of 0.16, NSE of 0.63, and R2 of 0.65 for irrigated crops. METRIC provided accurate hourly ET estimates that may be useful for irrigation scheduling and other water resources management purposes based on the hourly assessment.
Highlights
Evapotranspiration (ET) is one of the major components of the water budget
Performance statistics showed that satellite-based hourly estimates compared to lysimeter measurements provided good performance with an root-mean-square error(RMSE) of 0.14 mm, Nash–Sutcliffe efficiency (NSE) of 0.57, and R2 of 0.62 for ET for dryland crops, and RMSE of 0.16, NSE of 0.63, and R2 of 0.65 for irrigated crops
The METRIC model [25] was used to estimate ET, and an hourly evaluation was performed for surface temperature, solar radiation, soil heat flux, and evapotranspiration (Ts, Rn, Go, ET)
Summary
Evapotranspiration (ET) is one of the major components of the water budget. It plays a major role in the water cycle and irrigation water management [1,2]. ET measurement methods such as pan evaporation, sap flow, and weighing lysimeters are widely used. These measurements are considered point estimates for particular irrigation practices in a homogenous field. Other ET methods such as Bowen ratio, scintillometers, and eddy covariance can provide greater spatial coverage but may not adequately represent a watershed scale. Remote sensing models using satellite data can provide large-scale spatial coverage at various spatial resolutions [5,6].
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