Study of Groundwater Resources Components in the North China Plain based on Numerical Modeling

Abstract:

Over-exploitation of groundwater and induced environmental problems in the North China Plain (NCP) has drawn more and more concerns. Here, we chose three typical hydrogeological units in the NCP, which are Hutuo River alluvial fan (HR), the Tianjin Plain in the central alluvial fan (TJ), and the Yellow river aquifer system (YR). Relying on groundwater numerical models through MODFLOW, the water balances were calculated and analyzed accordingly, especially for quantifying individual recharge and discharge contributing terms. Specifically, (1) In the HR, both natural steady-state flow and transient flow models under human activities were implemented. Results indicated groundwater level decreased by around 40m with extensive exploitation, where the total recharge rate, discharge rate, and over-exploitation rate were calculated. (2) In the TJ, groundwater and land subsidence coupled model was established, where the maximum subsidence rate and decrease of groundwater level was estimated. (3) In the YR, the exploitation rate of the groundwater and recharge rate of the aquifer by the Yellow River were calculated.

We found that there are big differences among the components of groundwater recharge of the three typical hydrogeological units. Human activities have a clear effect on the recharge and discharge processes. Thus, rational development and protection policies should be issued. In the piedmont alluvial fan, the groundwater was severely over-exploited. Therefore, reduction of groundwater exploitation and groundwater artificial recharge are needed to get the recharge and discharge balanced. In the middle alluvial fan of the NCP, the confined aquifer has been over-exploited and has resulted in regional land subsidence. It suggests the withdrawal of confined aquifer should be strictly limited, especially at the place where alternative water resources are accessible. In the hydrogeological unit of the YR, the groundwater storage is potentially large for exploitation.