Estimation Of Evapotranspiration In Heihe River Basin

Evapotranspiration is an important part of the water and energy cycle, local regionalevapotranspiration will affect the water balance and climate energy in the local region, and theglobal terrestrial evapotranspiration will affect the climate, ecosystem balance, human life andproduction. Nowadays, it is short of freshwater resources in the global scale, and thedistribution is uneven extremely. Although the freshwater resources is power in China the percapita level is only1/4of the world’s. And the distribution is more uneven in our county. Atpresent, the problem of water resources has become a bottleneck, which is restricting thedevelopment of economic and social in China. Evapotranspiration as an important part of thewater cycle, the depth study of evapotranspiration plays an important role in the short-termwater cycle and long-term water resources planning and management, and it also has animportant guiding significance for long-term regional economic and social development.In the past, the studies were based on field evapotranspiration distributed sites analyzedobservational data. However there are many disadvantages for this method, such as highinvestment, long time consuming, and poor space-time. In recent years, as the rapiddevelopment of remote sensing inversion techniques, the use of remote sensing quantitativeinversion of regional evapotranspiration has become an important direction ofevapotranspiration. This technology exhibits high timeliness, large area and othercharacteristics.Heihe River Basin is the second largest inland river in Northwest of China, it offersnecessary support for the surrounding environment, ecological, social, economic and the otherfield in Heihe River Basin, but the middle and downstream area of Heihe River Basin is dryclimate, poor precipitation, strong solar radiation and wind, high difference in temperaturebetween day and night. With the increase of human activities, water supply is inadequate,leading to downstream area long time cutoff and lakes dried up in Heihe River Basin. So, theresearch of evapotranspiration in Heihe River basin has more important significance in thespatial distribution and temporal change both qualitatively and quantitatively. Heihe RiverBasin is an important and typically area of the northwest region, the study evapotranspirationin Heihe River Basin not only plays an important role in planning the use of water resourcesin western China, but also provides important reference value in planning and management ofwater resources in the Heihe River Basin.In this paper, we collected and sorted the MODIS data about Heihe River Basin, andcombined with ground-based observation data, adopted RS inversion theory and quantitativemethods to obtain vegetation index NDVI, leaf area index, surface emissivity, surface featuresand other important parameters of Heihe River Basin. In addition, we got the criticalvegetation index by image. Based on SEBAL model, this paper treated the surface parametersby inversion as input values to estimate evapotranspiration in Heihe River Basin, also analyzed the evapotranspiration mechanism and the causes of regional imbalance of HeiheRiver Basin.