Estimation Of Regional Water Conservation Based On SEBS And SCS Model

The article based on water balance, selected district of water conservation in northern Beijing, calculated actual terrestrial evapotranspiration using the surface energy balance system (SEBS), and measured the surface runoff via the SCS model combined with topography, so that it quantified regional water conservation accurately. By analysing the main influenced factors of the water conservation at regional-scale, the thesis gave some suggestions to regulate water conservation and gave a method to estimate regional water conservation. The main conclusions are as follows:(1) Estimation of evapotranspirationThe seasonal evapotranspiration was:summer>spring>autumn>winter. The average evapotranspiration in summer, winter, and annual was124.63mm,17.78mm,241.71mm, and respectively. The evaporation of forest, shrub, grassland, immature forest and water area are the largest, followed by sparse woods, farmland. Unused land and nursery land were the minimum.Related to temperature, NDVI, rainfall, surface temperature and land-use, the evapotranspiration increases with the temperature and NDVI values. The increase of rainfall enhances the available water, thereby increasing the evapotranspiration. Moreover, the evapotranspiration positively related with missivity, the total radiation, latent heat flux, net radiation, soil heat flux. The evapotranspiration were negatively correlated with surface albedo and sensible heat flux.(2) Estimation of runoffRunoff in study area mainly occured from May to August. Cumulative annual maximum runoff depth reached193.6mm, accounting for33.4%of total rainfall. The total of runoff was3.57×108m3,56294m3/km2. The region that produced runoff mainly distributed in farmland and unused land of western and southern area. Forest and region covered with grassland rarely produced runoff, expected heavy rainfall.Runoff was related with land use, soil texture. The average runoff depth of clay was38.10mm, which was the maximum, and took65.05%among the total runoff. The average runoff depth of farmland was the maximum, and reached127.23mm. The average runoff depth of shrub was the minimum, only4.98mm. The order of average runoff depth is, clay> loam> sandy loam> sand; farmland> unused land> sparse woods> grassland> forest land> nursery land> shrub.(3) Estimation of water conservationAccumulated maximum water conservation in study area reached514.27mm. Due to lower rainfall from January to April, September, November and December, the rainfall in the region were too small to make up the loss by evapor-transpiration. The water conservation in August was the highest, reached103.78mm. Annual water conservation in shrub was the largest, which reached514.27mm, and the lowest in grassland, reached471.2mm. Water conservation depth class is, shrub land> forest land> sparse woods> grassland.The results showed that based on water balance the method used SEBS and SCS model which has been compared with actual measurement of evaportranspiration to estimate regional water conservation was feasible. The conclusion that water conservation in shrub was the largest, it should be paid more attention in the future. Taking water conservation in shrub seriously and making rational use of vegetation community structure should be applied in future work.