Regional Evapotranspiration Estimation With Remotely Sensed Data In Minqin Oasis

Evapotranspiration plays a significant role in the earth's water and energy balance system. It affects regional and global climate, ecological environment and agricultural yield through the hydrological cycle. Currently, water management emphasis tends to shift from supply augmentation to limiting water consumption. Spatio-temporal information on actual evapotranspiration (ET) helps users to better understand evaporative depletion and to establish links between land use, water allocation, and water use.In a field, a common procedure to estimate ET under nonideal conditions is the three- stage modeling procedure: reference ET—crop coefficients—soil moisture term. Instead of being modeled, ET can be measured in situ in which Bowen ratio systems, Eddy- covariance systems, or lysimeters are used. However, these methods only provide representative results in a small scale because of the variability of regional ET.Remote sensing technique, which can provide representative regional surface parameters, has proven to be the only suitable approach to estimate large-area ET. remotely sensed measurements offer methods for extending point measurements to much larger areas. Secondly, remotely sensed measurements may be used to measure variables in the energy and moisture balance models of ET. For instance, the thermal band information can be used to retrieve surface temperature, which determines the net radiation.This article summarizes and evaluates widely used models that predict regional ET utilizing satellite remotely sensed data and routine meteorological data, and adopted SEBAL which has a solid physical foundation and enjoys world popularity to estimate daily ET of Minqin Oasis with the available Landsat TM/ETM+ data for three days.Two types of verification methods are used: 1) Point verification. The reference ET of the weather station in the research area is calculated by the Penman- Monteith model with the REF-ET software package. The potential ET is acquired by making a correction between the standard crop and the specific crop through the crop coefficient. Comparisons are made between the potential crop ET and the results from SEBAL.2).Region verification. Based on the meteorological data from all the seven weather stations of the river basin where the Minqin Oasis is located, the point potential ET is calculated. The regression analysis is made among longitude, latitude, DEM, slope, aspect of the seven points. With the regression...