Study On Groundwater Numerical Simulation And Sustainable Utilization In The Blown-sand Region Of The Northern Shaanxi Provience

Mineral resources of the blown-sand region in the northern Shaanxi province, national energy and chemical industry base, are abundant. Because the region is in the arid and semi-arid climate zone, rare precipitation and intense evaporation, so its environment is fragile and water resources are key confinement factors to its economical development. Directed by dynamic theories of groundwater, based on principle of sustainable development of water resource and pattern of water resource conversion among atmospheric precipitation, surface water and groundwater, combining with hydrogeological conditions, this paper evaluated the allowable withdrawal of regional groundwater resources of ecological safety-based by numerical stimulation theories and method of groundwater flow on the purpose of sustainable utilization of water resources, and proposed exploitation programs. Its research achievements are as follow.(1) The main water-bearing formation is generalized pore phreatic water with medium-fine sand in Quaternary alluvial-lacustrine deposits, fissure-pore pheratic water with sandstones in Luohe group, down Cretaceous system, Mesozoic Erathem and weathering fissure pheratic water of bedrock in Jurassic system. Then spatial structure model of water-bearing formations was established. All these provided base for the numerical stimulation model.(2) Field investigation showes that the supergene environment is good when buried depth of groundwater table ranges from 1.5m to5m. The buried depth of groundwater table to ecological safety is 3-5 meters in the region by synthetical analysis.(3) Groundwater resource quantity was evaluated by the means of hydrological balance (lumped parameter method). The result shows that the natural resource quantity of groundwater is 13.08×10~8m~3/a under mean annual condition, 12.58×10~8m~3/a under guaranteeing rate 50%, 10.56×10~8m~3/a under guaranteeing rate 75%, 5.90×10~8m~3/a under guaranteeing rate 95%, 11.18×10~8m~3/a in the current year (2005) in the blown-sand region of the northern Shaanxi Province. This conclusion provided the reliable evidence for verifying the results of numerical method.(4) According to the calibration and verification of the hydrogeological parameters, groundwater balance results, groundwater flow fields and drawdown fields, the groundwater flow mathematical model (distributed parameter type) was established with higher emulation and the programs were forecasted. The forecast results showed that its allowable withdrawal was 2.03×10~8m~3/a based on buried depth of groundwater table to the ecological safety, and that it had increased 0.85×10~8m~3/a than that of the current year.These research achievements above provide scientific evidence for rational exploitation of groundwater resources in the blown-sand region of the northern Shaanxi Province, these have important significance to sustainability of environment protection, industry and agriculture production and economy development.