Region ET Analysis And Water Resource Use Efficiency Assessment Based On Remote Sensing

Evapotranspiration(ET) is an important part of regional water-thermal cycle and accurately estimating evapotranspiration for optimal allocation of regional water resources is of great significant. With deeply research on the surface energy balance system and remote sensing technology matures, estimating evapotranspiration with remote sensing model becomes a quick, convenient and effective way to obtain regional scale evapotranspiration data. In the utilization of agriculture water, the remote sensing evapotranspiration model can accurate estimate the evapotranspiration of irrigated cropland and the water requirement of crop. Therefore, based on "useful consumption of water resource" and "useless consumption of water resource" concept, a method is proposed to evaluate the irrigation water use efficiency, which beneficial consumption of agricultural water resource is defined as the subtraction between evapotranspiration in arable land and effective rainfall.This research selects MODIS images and meteorological data of Yumenkou Yellow River irrigation areas during 2007 to 2012, and achieves SEBS(Surface Energy Balance System) model calculation, based on ENVI4.8 platform. Then, alot calculation work is done. Surface parameters of the study area, such as surface albedo, vegetation index, is calculated. The surface energy balance components is calculated. Finally daily evapotranspiration is got. By comparing the calculation results with daily evaporation data measured in meteorological stations, the accuracy of calculation is verified; Meanwhile, the spatial and temporal distribution features of Surface physical parameters, the surface energy balance fluxes and daily evapotranspiration is analyzed. The main research content are as follows:1. Data collection and preprocessing. Daily remote sensing data of Yumenkou Irrigation during 2007-2012 years, meteorological data, digital elevation data(DEM) and land-use data were collected.Then, the remote sensing image with cloudless over the study area is screened. Meanwhile, preprocessing is done for above data, including the projection transformation of remote sensing image, mosaicking, reduction of remote sensing image and bad value processing;resizing DEM data, reduction of DEM data, calculating slopes and aspect data,meteorological data collation and so on.2. Estimation of evapotranspiration from remote sensing and precision analysis. Relying on SEBS evapotranspiration model to calculate the surface energy fluxes, annual surface evapotranspiration is obtained in Yumenkou irrigated areas during 2007-2012. Meanwhile, combined the computation results of remote sensing model from 20 images in 2011 year, which quality is good,with meteorological data of Jishan meteorological station and Houmameteorological station, the evapotranspiration accuracy is testify. The results showed that: the estimated value of remote sensing have a good accuracy. The annual evapotranspiration variations are very small. The average ET of six-years is 760.97 mm.3. Exploring the spatial and temporal distribution of evapotranspiration. By the daily evaporation distribution of typical day, the spatial and temporal distribution regularity is explored. In the spatial distribution, due to the different types of land cover and the different cultivated crops of typical day, daily evapotranspiration shows different spatial distribution forms. But the daily evapotranspiration of mountainous and hilly areas are always higher. From the temporal change perspective, the daily evapotranspiration of July is the highest,April and September is followed, and the daily evapotranspiration of November is minimum.4. Made a discussion about the relationship between remote sensing evapotranspiration and land cover type. Spatial analysis is operated between surface evapotranspiration and land cover type map, using GIS software. The results shows that the surface evapotranspiration and land cover types are closely related. The regional evapotranspiration covered by forest is followed by grassland. Farmland and urban land is minimum.5. Irrigation water use efficiency evaluation. Combined with remote sensing evapotranspiration and the total water consumption of irrigation data,the irrigation water use efficiency is calculated, using water balance model.Then the irrigation water use efficiency of 2007-2012 years is evaluated. The results shows that the irrigation water use efficiency is between 51.3%-62.7%and the water use efficiency level is moderate.This method use evapotranspiration data calculated by remote sensing model and water balance model to evaluate water use efficiency, avoiding the complexity computation problem of ‘how much water reaches the crop root zone’. The required data acquire conveniently, timely, and quickly. The calculation process is simple. The results apply to Yumenkou irrigation area,having a important guiding significance to optimization and allocation of irrigation water resources.