Environmental risk-based hydroeconomic evaluation for alluvial aquifer management in arid river basin

Groundwater has resource, ecology, economy and society attributes. In recent years, ecological degradation caused by intensive groundwater exploitation to support socio-economic development has been of growing concern in arid and semiarid regions. To protect the groundwater sustained ecosystem, this paper developed a novel environmental risk-based hydroeconomic model to evaluate the tradeoff between groundwater utilization and ecological environmental protection in Golmud river catchment of Qaidam basin, a typical inland river watershed and alluvial aquifer, in northwestern China. Field survey, remote sensing and groundwater level monitor were conducted to obtain the threshold of groundwater dependent ecosystem. Results show that depth to groundwater table should be larger than 25.5 m in alluvial plain to prevent downstream Golmud city urban waterlogging, depth to groundwater table should be smaller than 10 m in groundwater overflow zone and fine soil plain to sustain groundwater dependent vegetation survive, and groundwater recharge to the terminal lake should be larger than 282.0 hm³ yr^-1 to maintain the minimum water surface area. Meanwhile, ecosystem services value was established according to equivalent value factors per unit area provided by different types of ecosystem in Golmud river catchment. Numerical simulations model was applied to evaluate the potential environment risk, cost and benefit of ecosystem services under different groundwater demand. The investigation results show that groundwater exploitation in 2030 with 240.9 hm³ yr^-1 will cause environment risk, which is terminal lake surface area smaller than permitted minimum threshold. And the recommended maximum amount of groundwater exploitation is 219.0 hm³ yr^-1. This study provides guidance for regional groundwater management to maintain environment protection and socio-economy development, especially in arid regions.