Groundwater Risk Assessment of the Third Aquifer in Tianjin City, China

More than 70 % of Tianjin city’s water supply comes from groundwater. As water demand increases, this reliance on groundwater has caused serious geological problems, such as seawater intrusion. The third aquifer is the main water supply aquifer for Tianjin city. According to supply conditions, water abundance, exploitation conditions, and water quality of the third aquifer, the type of ecological environment system, protection targets and requirements, the present situation of groundwater exploitation and utilization, the groundwater exploitation demand, and utilization for regional water resources allocation as well as national overall scheme about reasonable exploitation, utilization and protection of groundwater resource, groundwater in Tianjin has been divided into seven function areas. After analysis of influencing factors, like water abundance, exploitation intensity and well density, risk factors have been classified using AHP and GIS. Then the comprehensive evaluation model of groundwater exploitation and utilization risks was built. Using this model, the exploitation and utilization risks of the third aquifer in years 2015, 2020, and 2030 have been forecasted. The results show that the risk grade of this aquifer in 2015 is higher than now, while lower in 2020 and 2030. But the risk grade of the 3rd and 4th aquifer increases, since the water yield of this aquifer must still meet a certain amount to support the basic demand of this city.