Studies Estimate The Amount Of Precipitation Recharge Beijing-based Remote Sensing

The annual average rainfall is590.25mm in the year of1951-2011of Beijing. More than two-thirds of the city water supply is relied on groundwater. Beijing is a water shortage city. Because of eight consecutive years of drought between1999and2007, Beijing is facing a severe water crisis. The shortage of water resources seriously restricts the sustainable development of Beijing social and economic.Traditional groundwater observation and model simulation methods have several problems, such as space limitations, parameter uncertainty, and so on. The method in this paper is based on remote sensing and geographic information system technology. Groundwater recharge in Beijing is calculated with the principle of water balance. Underground water level dynamic equilibrium method is used to verify the applicability of the method. Specific contents as follows:(1) Estimating the groundwater recharge of Beijing in2011. This paper choosed the remote sensing data, MODIS and TRMM data, which is easy to get as the source of initial data. And this paper got the result of groundwater recharge of Beijing in2011. The groundwater recharge is555.36mm-555.36mm, with a mean of174.80mm. The total recharge in the study area is2.396billion m3. The mountain area groundwater recharge is1.078billion m3, and the plain area groundwater recharge is1.318billion m3.(2) Validation of the result which is based on remote sensing of water balance method. In this paper, at the same time, underground water level dynamic equilibrium method is used to calculate groundwater recharge in2011. This paper had compared the results of the two methods. Results show that the calculated by two methods of Beijing drainage system around the groundwater recharge has very high correlation, R2=0.90,RMSE=0.69x108m3. The result based on remote sensing is generally less than the result based on the underground water level dynamic method. From the high correlation can obtain that the method based on remote sensing of water balance has certain applicability when calculating the vertical infiltration recharge in Beijing.(3) Groundwater recharge impact factors analysis. The groundwater recharge is the least where there is woodland. And it is large where there is settlements and wetlands. The groundwater recharge is maximum when the value of NDVI is around0.4, and groundwater recharge decreases with the increase of NDVI. This can be concluded that at present Beijing extensive plain afforestation activities will reduce groundwater recharge. Surface soil texture on groundwater recharge effect is not obvious, the size of the groundwater recharge is affected by soil texture is smaller.