Risk Assessment of Groundwater and its Application. Part I: Risk Grading Based on the Functional Zoning of Groundwater

The functional zoning of groundwater is the basis for the rational development and utilization, scientific management and effective protection of groundwater. Based on the distribution, type, hydrogeological condition and exploitation status of groundwater in Tianjin, and considering the resource supply, ecological environment maintenance and geological environment stability simultaneously, the function zoning of shallow groundwater has been divided into the non-central water supply area in built-up zones, the fragile marsh zones, the fragile nature reserve zones, the polluted groundwater zones and the salt water zones. And the deep groundwater has been divided into the non-central water supply area in built-up zones, the central supply area in built-up zones, the land subsidence zones, polluted groundwater zones and the salt water descending zones. Firstly, this paper selected dominant factors of groundwater development and utilization risk based on the different groundwater function zoning results, distinguished them into natural factors and human factors, and developed the risk assessment index systems. Secondly, the risk assessment systems for shallow and deep groundwater were built according to the characteristics of respective aquifers, and the weight of each evaluation index was calculated by AHP (Analytic Hierarchy Process) method. Then, each of the unit risk grade was determined by the method of fuzzy synthetic evaluation on basis of these index attributes and the corresponding weights, and results were distributed in space using ArcGIS to obtain the groundwater risk grade map of various aquifers in different groundwater function zones of Tianjin city. Finally, the risk grade in each district of Tianjin was determined by superimposing the district boundaries on these maps. Groundwater development and utilization risk grades based on the functional zoning of groundwater can provide a scientific basis for management of groundwater and a method for determining groundwater level.