The effects of artificial recharge of groundwater on controlling land subsidence and its influence on groundwater quality and aquifer energy storage in Shanghai, China

Long-term groundwater overpumping in Shanghai has caused serious land subsidence. To restore the declined piezometric groundwater levels and to decrease the land subsidence rate, artificial recharge (AR) of groundwater into confined aquifers through injected wells has been proposed as an important measurement since the beginning of the 1960s. In the case of Shanghai, recharge source is tap water, whose chemical constituents and temperature are different from groundwater. Consequently, the issues of groundwater quality change and thermal energy are worthy of discussion. In this paper, we discussed the influences of AR for controlling land subsidence on: (1) groundwater level and land subsidence rate, (2) groundwater quality, (3) aquifer thermal energy storage. The results based on the collected long-term historical data in the study area show that AR not only is beneficial to groundwater level rising and land rebound, but also provides cheap energy sources for industrial production. The groundwater quality presented the trend of desalination and a general increase in sulfate, iron and manganese contents, organic and nitrogenous compounds after the tap water injection. However, the AR’s influence on groundwater quality was limited, with the radius <100 m for single-well recharge and <1000 m for well groups recharge. To control the development of the land subsidence within a safe limit in the study area, the injected confined aquifers and the distribution of the AR wells need to be further adjusted due to the limitation of current AR.