Study Of The Influence Of The Second Fenhe River Reservoir Storage On Lancun Karst Water And Pore Water In Xizhang Basin

The second Fenhe reservoir is an important water supply source to Taiyuan, which located in the carbonatite distribution area of northwest of Taiyuan. The Lancun water source and Xizhang Basin are in downstream of the dam. The study of the influence to Lancun karst water and Xizhang basin storage water after impoundment of the second Fenhe reservoir, give some guidance on the storage operation and management of the second Fenhe reservoir.Based on the summarize of research achievement at home and abroad, the analysis of areal geology, condition of hydrogeololgy, current development and utilization of groundwater, this paper utilize the karst water level around the second Fenhe reservoir and the variation of groundwater regime to discuss the functional dependency between Lancun karst water level and different kinds of source and sink terms by the method of the correlation analysis, establish the multiple regression model of Lancun water source, predict and analyze the dynamic change of karst water level of different impounding schemes in 2015, develop the hydrogeology conception model and the mathematical model of Xizhang basin, utilize the 3D numerical simulation software-Visual Modflow to solve the mathematical model, identify and verify the model by using of the measured data, make an water balance analysis for this area. At last, this paper also forecast the pore water level change of Xizhang basin, based on different impounding schemes in 2015. In order to achieve the sustainable utilization of region water resources, the research result is able to provide evidence for the rational exploitation and utilization, the joint regulation and storage of surface water and groundwater. The main contents and conclusions are as follows:Karst groundwater level of the Lancun water source can be used multivariate linear model to forecast, when the second Fenhe reservoir is not stored, the observation borehole S1 water level is 775.94m. When the reservoir water level maintains in the dead storage level (880m), the observation borehole S1 water level is 775.94m. When the second Fenhe reservoir water level is normal water level (905.7m), the observation borehole S1 water level is 776.71m. In the case of reservoir water level is normal or nonstorage, the second Fenhe reservoir storage has little effect on karst groundwater level in the Lancun water source, which made the borehole water level changes only 0.77m.Using MODFLOW software, the regional water balance analysis in Xizhang basin showed that, when the reservoir water level maintains in the dead storage level, the total recharge of groundwater system is 9346.965 million m3 per annual (which not include the interaquifer flow between two aquifers). The total discharge is 6920.692. It takes on appositive budget in this area, the budget is 0.243 million m3 per annual。Artificial mining is the main discharge item of porous groundwater in the Xinzhang basin. It plays a vital role on the local groundwater circulation.The Xizhang basin porous groundwater has been in recovery Since the Taiyuan city take the measure of shut-down well for limiting exploitation. When the second Fenhe reservoir is not stored, keep the present level and in the dead storage level, the regional water elevation changes between 786m and 814m in 2015, the water level increases 5～15m. When the reservoir water level resches normal water level, shallow groundwater level is only higher 2～4m than nonstorage. It can clearly be seen that the second Fenhe reservoir storage has little effect on the Xizhang basin poro groundwater level.