Study On The Temporal And Spatial Inversion Of Evapotranspiration Over Hetao Plain

The ecological environment is very fragile in Hetao Plain in the arid and semi-arid areas. The lack of scientific use of regional water resources management caused the contradiction of desertification and salinization. Base on the research of regional water cycle, the scientific and rational allocation is an urgent problem about the development and utilization of water resources. The evapotranspiration is the important aspect in the region resource cycle. It is important to master the rule of the distribution about evapotranspiration for the suitable management of region water resource.In this paper, the envi4.2+idl6.2 operating platform is used to compile the program based on the SEBS principle. By choosing the suitable parameters formula, combining ground site observation, and using the MODIS/TERRA satellite remote sensing images, the surface parameters was calculated. Then the instant net surface radiation, soil heat flux at the satellite crossing and the daily evapotranspiration could be calculated.The theoretical evapotranspiration was calculated by P-M formula, and the rule of distribution was analysised. Then the rule was used to calculate the distribution of the real evapotranspiration. The temporal distribution characteristic of evapotranspiration shows that there is relationship between the evapotranspiration, water level and surface coverage. The spatial distribution in study area shows: water> mountain> vegetation> Saudi> bare land. And the temporal distribution has a clear correlation with precipitation and water level.After the research of distribution, the sensitivity analysis of remote sensed parameters was calculated. Under the condition of same change of albedo, sensitivity of the daily mean ET on ALBEDO over different land cover type is sequenced as follows: desert > bareness> cropland > mountain >water. With the same change of NDVI, sensitivity of the daily mean ET on NDVI over different land cover type is sequenced as follows: mountain> bareness> desert > cropland >water.Finally, using the average annual evaporation deducted from the remote sensing, the regional water balance was analysised. And the new way to analysis the region water balance provide the scientific basis of rational plan about water resource.