Using Remote Sensing to Estimate Evapotranspiration of Irrigated Crops Under Flood and Sprinkler Irrigation Systems

Abstract

AbstractThe objectives of this study are to: (i) estimate the actual evapotranspiration (ETa) of the different irrigated crops in the South Platte River Basin, Colorado, USA; (ii) compare the consumption use for the irrigated areas for 2001 and 2010; (iii) investigate the impact of irrigation system (flood/sprinkler) on the estimated ETa. The ReSET model, a surface energy balance remote sensing based model, is used in this study to estimate the ETa of the South Platte River Basin irrigated crops for 2001 and 2010. Landsat 5/7 satellite images, weather data, shape files of irrigated crops, and a digital elevation model (DEM) were acquired and processed for the study area. The results of this study show that the estimated ETa using the ReSET model showed a reduction of 7.1% from 2.51 × 109 m3 in 2001 to 2.33 × 109 m3 in 2010, mainly due to the reduction of the irrigated area from 2001 to 2010 by 6.6%. The estimated total ETa of crops irrigated with flood irrigation systems decreased from 66.1 to 54.6%, while the estimated total ETa of crops irrigated with sprinkler systems increased from 33.9 to 45.4%. For 2001, the average seasonal ETa of all crops for flood irrigation and sprinkler irrigation, respectively, were 665 and 712 mm, with a 7% greater ETa for sprinkler systems. The ReSET model ETa estimates have been validated in a previous study of lysimeter measurements. However, in this study and due to the unavailability of a lysimeter, the model ETa estimates were verified with the reference evapotranspiration (ETr) of the weather stations in the study area. The results of the t‐test shows a p‐value = 0.124, greater than 0.05, which indicates that the means of the ReSET ETa estimates and the ETr are not significantly different. Additionally, the results of the F‐test shows a p‐value = 0.674, greater than 0.05, which indicates that the two variances of the ReSET ETa estimates and the ETr are homogeneous. Copyright © 2015 John Wiley & Sons, Ltd.