Evaluating Allowable Yield Of Groundwater By Using MODFLOW In Datong County

The groundwater resources play an important role in water supply for industry, agriculture, urban and rural residents living and drinking in Datong County. The sustainable utilization of groundwater resources has related to the sustainable development of society and economy can be realized in Datong County. Groundwater exploitation of Datong County mainly focuses on phreatic aquifer near the surface ground. So the water quality and quantitly of the aquifer become the focus question that the local government and public pay close attention to. To solve these problems, this paper evaluates the groundwater resources according to water balance and numerical simulation theory, based on fully collecting relative data and former study.According to geographic and geomorphic conditions, geology and hydrogeology conditions, the blunt flood plain and volcanic hilly areas are determined for evaluation region. Using the water balance theory, it evaluated the groundwater resources is totally74.534million per year in evaluation region.Based on groundwater quality monitoring data of Datong County in2008, groundwater quality of Datong Country is evaluated by adopting single component evaluation, integrated components evaluation and coefficient method. The results show that quality level of groundwater in Datong County basically is IV level, even V in specific areas. The overweight items of groundwater are pH, fluoride, and bacteria number. Through assessment for drinking water quality, except the quality of drinking water in Yongsheng village and Jule village fulfill the standard, all the rest groundwater are not meet the standard of drinking water.Based on geographic and geomorphic conditions, geology and hydrogeology conditions, the conceptual hydrogeological model is established. And it conducts parameter partition according to the watery characteristics of water aquifer. The boundary condition, initial condition of aquifer and source and sink term of model is generalized. The identification and confirmation of numerical model are conducted by making use of existing data of long-term observation wells. The results show that the conceptual hydrogeological model is basic accord with the actual, the model better reflect the characteristics of underground water, can predict groundwater table.The main recharge and discharge term of simulated domain are calculated, such as rainfall infiltration recharge, riverway infiltration recharge, surface water infiltration recharge, lateral recharge, phreatic water evaporation, lateral spring excretion and so on. Combined with aritificial exploitation yield, water balance status of phreatic aquifer is analyzed. The results show that the charge of aquifer storage in regional is positive equilibrium.Taking2015as forecast year, using the numerical model, predicted under the groundwater exploitation maintains33.6million cubic metres per year(2008is below) and the groundwater exploitation increases to52.45million cubic metres per year(Allowable Yield of Groundwater) in25%,50%, and75%of the underground water level under rainfall assurance rate in change tendency of groundwater table. Based on the simulated results, it comparatively analyzed change condition of groundwater level under two different mining schemes and confirmed the allowable yield of groundwater is52.45million cubic metres per year in Datong County.