The Impact On The Surrounding Groundwater Level By Yu Yang Mineral Exploitation

Yulin city is located in northern Shaanxi, which is the arid and semi-arid area. Thenatural condition is very bad and the ecological environment is very fragile. The miningindustry was regarded as the energy pillar industry of Yulin city. The mining industry not onlyquickly improves the local economy but also destroys the underground water resource andenvironment because of excessive exploitation. Along with the rapidly growth of minedrainage and practical water consumption in the process of coal mining, the undergroundwater level continually declines. If we did not take appropriate measures to preventgroundwater level from declining, the permanent and unrecoverable cone of depression wouldbe generated nearby the coal mine at last. There are many environmental geology problemssuch as land subsidence and ground fracture and so on would be aroused. Meanwhile if wedid not take scientific, reasonable and effective measures to protect groundwater environmentfrom deteriorating in the process of mineral exploitation, the problem of the critical shortageand the imbalance between supply and demand of water resources would become worse andworse. Therefore, it is necessary to evaluate and predict the surrounding groundwater levelchange in the situation of Yu Yang mineral resources exploitation and to provide theoreticaland technical support for the sustainable development in this region.In this paper, hydrogeological conceptual model, three-dimensional geometric model andthree-dimensional hydrogeological model was established based upon the practical geologicaland hydrogeological conditions were ascertained in the study area. Firstly thethree-dimensional hydrogeological model should be recognized and verified. The results fromthe recognition and verification proved that the three-dimensional hydrogeological modelcould be used as the evaluation research about the changes of surrounding groundwater levelunder the conditions of Yu Yang mineral exploitation. Based on these models, the situation ofgush-out water, the changes of groundwater level and flow distribution were simulated atdifferent times under the exploitation condition. In accordance with the calculated resultsthrough simulating, the influence on the surrounding groundwater level under the conditionsof Yu Yang mineral exploitation was analyzed in detail. Due to the changes of water level and surface area of Yuxi River affect groundwater level to some extent, so it is necessary toresearch the changes of groundwater level and flow distribution under the conditions ofdifferent water level and surface area. The following conclusions were summarized in thispaper:1. The natural flow distribution was served as initial flow distribution and20yearstransient flow model under the conditions of Yu Yang mineral exploitation was simulated. Theresults show that the drawdown is larger in the coal mine area than other places in the studyarea because of the mine drainage. The drawdown declines gradually along with keepingaway from coal mine. Then a cone of depression centered on the coal mine forms. Over timethe range of the cone of depression and the drawdown continuously increased.2. The calculated steady flow distribution generated from the simulation of the modelwhich including pumping in Hong Shixia water source region was served as initial flowdistribution and20years transient flow model under the conditions of Yu Yang mineralexploitation was simulated. The results show that the drawdown at different times in HongShixia water source region. After one year Yu Yang mineral exploitation the drawdown inHong Shixia water source region is below one meter. The range in which drawdown is greaterthan0.5m is0.09km2. After twenty years Yu Yang mineral exploitation the drawdown in HongShixia water source region is below ten meters. The range in which drawdown is greater than1m is18.29km2, and in which drawdown is greater than5m is2.9km2, and in whichdrawdown is greater than9m is0.09km2. Pumping groundwater in Hong Shixia water sourceregion can motivate surrounding water source region recharge Hong Shixia water sourceregion. Yu Yang coal mine is located in Ma He water source region that is in the upriver ofHong Shixia water source region. Mine drainage is mainly from groundwater in Ma He watersource region aquifer. So groundwater recharge that is from Ma He water source region toHong Shixia water source region decreased year after year.3. In the study area mineral exploitation and the change of surface water can influencesurrounding groundwater table. River in Hong Shixia water source region rechargesgroundwater mainly because of pumping. Following the decline of Yuxi River level, thecapacity of recharging groundwater by river goes down. Due to the decreased groundwaterrecharge source and the constant pumping yield, groundwater level drops continuously in Hong Shixia water source region. In this research the Conductance of river can describe thesurface area of Yuxi River. Because the pumping yield in Hong Shixia water source region isrelatively small and permeability coefficient of riverbed is relatively large, river can beregarded as the first kind boundary. Many trials indicate that within the200～2000m2/d ofConductance the change of groundwater level is not obvious. So the surface area of YuxiRiver reduced to a certain degree, which will not influence the groundwater level in HongShixia water source region.