Comparative Analysis of METRIC Model and Atmometer Methods for Estimating Actual Evapotranspiration

Accurate estimation of crop evapotranspiration (ET) is a key factor in agricultural water management including irrigated agriculture. The objective of this study was to compare ET estimated from the satellite-based remote sensing METRIC model to in situ atmometer readings. Atmometer readings were recorded from three sites in eastern South Dakota every morning between 8:15 and 8:30 AM for the duration of the 2016 growing season. Seven corresponding clear sky images from Landsat 7 and Landsat 8 (Path 29, Row 29) were processed and used for comparison. Three corn fields in three sites were used to compare actual evapotranspiration (). The results showed a good relationship between estimated by the METRIC model (-METRIC) and estimated with atmometer (-atm) ( = 0.87, index of agreement of 0.84, and RMSE = 0.65 mm day−1). However, -atm values were consistently lower than -METRIC values. The differences in daily between the two methods increase with high wind speed values (>4 m s−1). Results from this study are useful for improving irrigation water management at local and field scales.

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