Study On The Groundwater Vulnerability Of Shiyang River Basin

Shiyang River Basin is located in the west arid area of China, with the low precipitation, arid climate, poor water resources and fragile eco-environment, and the rational development and utilization of groundwater is of vital importance to the development of social economy and protection of eco-environment. However,with the utilization of water resources for the development of oasis agriculture,the impact of exterior environment on the function of groundwater became more and more stronger accompanied with a lot of problems,such as such as the deteriorative adjust ability of water aquifer, the exhaust and contamination of groundwater, vegetation deterioration, desertification and salinization of sand,and so on. Henceforth, research of the mechanism, characteristic, evaluation system and methods of groundwater vulnerability of the river basin has important theoretical and practical meaning on the sustainable development of groundwater resources and reconstruction of eco-environment.Based on the analysis of the basic conception, structure,the attribute of resources and environment of groundwater system, the groundwater system was generalized. On the basis of the generalization of groundwater system, the function, environment, connotation and expressive characteristic were analyzed and the conception of groundwater vulnerability was defined.The groundwater system of the river basin is an open natural-artifical compound one, of which, as a core, groundwater contact with human activity, eco-environment, and surface water closely. However, human activity, eco-environment, and surface water contact with each other, which influences groundwater furtherly. According to this, the vulnerability mechanism of the groundwater system was revealed from the three aspects of natural factors, human activities and eco-environmental factors.From the viewpoint of the input, groundwater entity and output of groundwater system, and also taking the function of the vulnerability mechanism, that is the influence of natural factors, human activities and eco-environmental factors into consideration, nine indicators of precipitation, groundwater recharge per square kilometer, utilization ratio of groundwater, transmissibility,embedded depth of groundwater, mineralization degree, nitrate content and total hardness were selected as the appraisal indicator system. And then, the indicator zoning were obtained based on the combination of the useful attributive information extracted by GIS and data.On the platform of the GIS software?MapInfo,69 appraisal parts were divided according to the dynamitic observation holes of groundwater, for which, the method of overall indicators was adopted to evaluate the groundwater vulnerability. The map of groundwater vulnerability grades was drawed by using the thematic map function of MapInfo, on the basis of which, the evaluation results were analyzed making use of the inquiry and statistics function. During all the steps, the application of GIS in the groundwater vulnerability evaluation was discussed.At last, the application of the methods of gray projection and ANN based on MATLAB in the groundwater vulnerability were also discussed to make comparison, and then the evaluation results were also presented in the way of map based on MapInfo. The analysis proved that the evaluation results of the three methods of overall indicators method gray projection and ANN based on MATLAB were in good agreement. The evaluation results showed that in 90% area of the river basin, the groundwater vulnerability was very serious and serious. For Minqin basin, the groundwater vulnerability was in the stage from being very serious to extremely serious, and for Wuwei basin, in the stage of being serious to very serious. Totally speaking, the groundwater vulnerability in Minqin Basin was more serious than Wuwei Basin.