Controlling factors identification of groundwater system evolution based on numerical simulation in the typical arid-inland basin

Groundwater resource is the basic power for the socio-economic development of arid-inland basins, and is also the major factor affecting the ecological environment of the Huangqihai Lake. As a typical study area of arid-inland basins, with the lowering of groundwater levels in recent years, the total area of the Huangqihai Lake decreases and even faces the risk of drying up. To quantitatively analyze the spatial-temporal evolution of groundwater resources in the Huangqihai Basin and the transformation relationship between lake water and groundwater, a numerical simulation model of groundwater flow in the Huangqihai Basin is established. The model is calibrated and validated by using long-term observation data from 2010 to 2016. The simulation results show that the accumulative deficit of groundwater storage in the Huangqihai Basin is 1.5×10⁸ m³ from 2010 to 2016, and over-exploitation of groundwater is the critical reason for the negative water balance in this area. The Sobol method is used to identify the controlling factors affecting the changes of groundwater resources in this area. The sensitivity of eight main parameters affecting the groundwater system is evaluated by using four objective functions: lake stage, lake leakage, groundwater storage and groundwater discharge to lake. There are significant differences in sensitivity analysis results of model parameters under different objective functions. The first two functions are significantly affected by the horizontal permeability and lake leakage rate, while the last two are mainly affected by exploitation and recharge from precipitation and irrigation. It is proved that the influence of over-exploitation of groundwater is the main controlling factor of the depletion of water resources and shrinking of lake area in the Huangqihai Basin. The results of this study can provide technical support and scientific decision making for the sustainable utilization of groundwater resources and the protection of surrounding ecological environment in the Huangqihai Basin.