Study On Groundwater Vulnerability

Groundwater vulnerability reflects the relative potential possibility of groundwater system to be polluted. The results of groundwater vulnerability research can provide a useful tool in land use planning, groundwater protection planning and groundwater quality monitoring. They can also help the pubic know more about groundwater pollution risk and have the idea of prevention taking priority in groundwater protection.There are three major classes of groundwater vulnerability assessment methods: overlay and index methods, methods employing process-based simulation models and statistical methods. The above three classes of methods all have their own advantages and disadvantages. Using the research experiences gained home and abroad for reference, groundwater vulnerability is systematically studied further in this paper. Taking Tangshan plain area as the study area and based on the specific conditions of the study area, six parameters such as depth to groundwater are selected to form the vulnerability assessment factor system and an integrated groundwater vulnerability model is developed which has been successfully applied in the intrinsic vulnerability assessment in Tangshan plain area. The model has overlay and index method as the basic, mathematical model and statistical method embedded to form an integrated model. The HYDRUS model is performed to obtain the rating system, and principal component analysis and factor analysis are used to get the weighting system. The integrated model employs three major classes of groundwater vulnerability assessment methods that are used together to overcome the shortcomings of the single class of methods and tostrengthen the objective and scientific foundation of the assessment results. WOE (Weights of evidence) method is used to study the pecific vulnerability of nitrate nitrogen in Tangshan plain area, which is conducted on the extension module of Arc-SDM with ArcView GIS software as the platform. Farmyard manure application amount and other seven parameters are selected as predictor variables and nitrate nitrogen is the response variable. WOE method is used to obtain the posterior probability distribution map of nitrate nitrogen concentration greater than 10mg/L. The objectivity and reasonability of the output is tested through various methods.The integrated vulnerability model is also applied in Beijing plain area and the central town drinking water source protective zones in Beijing suburb to assess groundwater vulnerability. The study results provide a useful tool for analyzing and forecasting the influence of storm water runoff retention to groundwater environment and for groundwater protection in drinking water source protective zones separately.