Study On Groundwater Resources And Hydroecologic Effect Caused By Coal Mining In The Coal Distribution Region Of The Northern Shaanxi Provience

The blown-sand region in the northern Shaanxi Provience, a large-scale urgent development region, in which the Jurassic coalfield is one of the largest ones about coal resources, is located in the middle-east part of the Odors Basin and the intermediate zone between the Maowusu desert and the loess plateau. However, the initial exploitation has caused irrecoverable damage to the regional eco-environments, especially to groundwater resources. Aimed at the sustainable utilization of groundwater and coal resources, on the basis of the hydrogeological and coalgeological conditions and groundwater system elements, this paper analysed the hydroecologic effect, assessed the regional groundwater resources ecology-oriented and simulated the leakage of groundwater resources caused by coal mining by method of a groundwater flow model, and also proposed the measures about the rational exploitation of coal resources and the protection of the groundwater resources. Its research achievements were as follow.1.Groundwater resource quantity of coal distribution region in the northern Shaanxi province was assessed by means of hydrological balance. The result showed that the natural resource quantity of groundwater was 18.97×108m3/a under an annual mean condition, 18.23×108m3/a under guaranteeing rate 50%, 15.28×108m3/a under guaranteeing rate 75%, and 8.44×108m3/a under guaranteeing rate 95%.2.Adjusting the reduction of the base flow to 10% of all the sum rivers and of that to 5% of the main tributary streams, controlling the buried depth of groundwater table between 3m and 5m and the basically equilibrium groundwater system state are the assessment principles of the allowable withdrawal ecology-oriented on groundwater resources.3.The allowable withdrawal of groundwater resources in this region was 6.26×108m3/a by numerical simulation, that in the loess-hilly part 1.93×108m3/a by means of production coefficient, and that of the whole region 8.19×108m3/a, the exploitation toplimit.4.The influence on the groundwater resources caused by coal mining of undeveloped areas has been simulated by the model above in the Yulin-Shenfu mining area. The simulation result shows that the leakage per a crack is 470m3/km·d in the drafted depression area.5.According to the results of the numerical simulation and the hydrogeological conditions, this paper proposed the countermeasures against coal mining with water conservation on the purpose of protecting groundwater resources and eco-environments in the coal distribution region.These research achievements above provided scientific decision evidence for rational exploitation of coal resources and the protection of groundwater resources and eco-environments.