| Evapotranspiration (ET) plays an important role in the hydrological cycle,about 66 percent of precipitation return to atmosphere on the land. ET includes evaporation and transpiration, which is directly influenced by meteorological conditions(radiation, temperature, precipitation,wind speed) and surface characteristics (vegetation cover, soil moisture, landscapes etc). Estimation of regional ET measuremens is still a difficult issue in water resources assessment. Traditional method using measurements of evaporation pan represented to regional ET couldn't meet scientific requirements. Newly method based on remote sensing data for ET estimation is a new technique in water resources and environment.Hailiutu River Basin, located in arid and semi-arid region northwestern china,is in abundant sunshine, less rainfall, and it is one of the areas with weakest ecological environment. Erdos plateau is rich in Coal and oil, but water shortage has seriously impede the economic and social development, especially in recent years, unreasonable utilization of water resource aggravate the deterioration of ecological environment in the Hailiutu River Basin. Based on hydrological mesurement data, the annual runoff was decreased half in Hanjiamao station.. Simultaneously, groundwater level is dropped significantly, vegetation degenerated severely,and the land turned into desert gradually.According to water budget and Empirical formula, We estimated the land surface TE of the Hailiutu River Basin,the average ET was about 281mm and 253mm, respectively Using cloud-free NOAA/MODIS data and SEBS (Surface Energy Balance System) model, this paper calculated the ET is 259.7 mm in 2008.The impact of vegetation cover, meteorological factor, topography, hydrogeology and landuse was also analyzed in this thesis. Based on ArcGIS, each impact factors was value assigned, superposed and finally the spatial distribution was mapped in this thesis. |
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