Research On The Numerical Simulation And Sustainable Utilization Of Groundwater In Qian'an Of China

Qian'an County is located in the northwest of Jilin province of china. Groundwater is the main source of water supply in the region. There are currently 2 water sources for municipal water supply in Qian'an; laying 12 pumping wells with an exploitation of 2.3×10⁴m³/d. The current water supply capacity can only meet the demands of the residents in the old urban area. With continuous economic development and growth in population, the demand for water resources is on an increasing trend. According to statistics, current exploitation in the area has reached 7102.76×10⁴m³/a. Domestic and industrial demands for water in the new urban area can not be satisfied by current water supply capacity of tap water companies in the region. To remedy this problem, enterprises and institutions have to add self-contained wells in their background which is making exploitation out of proportion. It is vey nessesary to assess groundwater resources, analyze current development and utilization of groundwater, calculate available groundwater resources, analyze the potential of groundwater, and raise the contermesure for groundwater sustainable utilization.The main aquifers of Qian'an County are porous unconfined aquifer of Quaternary unconsolidated formation, porous confined aquifer of Quaternary unconsolidated formation and porous and fracture confined aquifer of Tertiary fragmentary formation. The groundwater dynamic types of these layers aquifers are precitation-evaporation type, runoff-exploitation type and runoff type. The main groundwater chemical types of unconfined water are HCO₃-Mg, HCO₃Cl-NaMg, ClHCO₃-NaMg, HCO₃-CaNa, and HCO₃-Na. The maingroundwater chemical types of confined water are HCO₃-Ca, HCO₃-CaNa and HCO₃-NaCa. The variation of groundwater flow in the study area is predicted with GMS software, and the numeric groundwater model is identified and validated firstly according to the dynamic data of groundwater level from January 2008 to December 2008. The groundwater level shows the generalization of the structure and boundary of aquifers. The selections of hydrogeologic parameters are proper which truly reflects the characteristics of aquifers and the model is then used to predict the water level. The variation of groundwater level and flow in the region is predicted. Prediction result shows that the variation of groundwater level is mainly influenced by human exploitation.Analytic method is adopted to calculate the quantity of groundwater resources in Qian'an County. Groundwater recharge mainly comes from precipitation and side runoff. The average annual quantity of groundwater recharge is 22573.4×10⁴m³/a. Groundwater discharge is mainly of evaporation of unconfined water, side runoff and artificial exploitation. The quantity of groundwater discharge in 2008 is 22910×10⁴m³. Pumping Coefficient method and Uniform Wells method are adopted to calculate the average annual available groundwater resources in Qian'an County. The result of calculation is 15650.18×10⁴m³/a. Current groundwater exploitation quantity is 7102.76×10⁴m³/a, and the residual resources is 8547.4210⁴m³/a, existing certain potential for development.Bossel index system is selected to assess the development of sustainable utilization of groundwater resources in the area in the year 2008. The comprehensive index of groundwater sustainable utilization is 1.7866 in Qian'an County in 2008, belonging to the dangerous class. The water resources subsystem is relatively good, but the situation of Socio-economic subsystem and Environment subsystem is dangerous, influencing the whole groundwater sustainable system. With the development of socio-economy and improvement of technique standard, the Socio-economic subsystem and Environment subsystem will be much more improved, the sustainable situation will be better, influencing the whole system from a benifical side. The current situation of water resources subsystem is good, but the"existence"condition is poor with limited groundwater resources. Therefore, with the water demands increasing, the groundwater exploitation quantity will also increase, degrading the sustainable situation, influencing the whole system from a bad side. In order to guarantee the sustainable utilization of groundwater resources, it is necessary to develop socio-economy, improve technique standard, restrict groundwater exploitation, and save water resources.