Numerical simulation studies of the influences of water transferring project from the Haerteng River to the Dang River on groundwater levels in the Dunhuang Basin

The objective of the Integrated Planning of Rational Water Resources Utilization and Ecological Protection (2011-2020) issued by the State Council is to relieve the contradiction of reasonable water resource utilization and ecological protection. After the implement of the planning in recent years, visible water area is added, and the necessities of the planning is doubted. Groundwater is an important water source, and is also one of key factors affecting the ecology in the Xihu Nature Protection Area. Aiming at an quantitative analysis of the tempo-spatial changes of groundwater levels under different transferred scenarios, this study establishes a three-dimensional groundwater flow numerical model, and calibrates and verifies the model using much data such as long-term observation well data and additional water level data obtained through field investigation. The model results show that groundwater storage in the study area is under a negative equilibrium state with a yearly average value of 0.04×10⁸ m³, mainly distributed in the Danghe alluvial fan and the north part of the Dang River irrigation area. The yearly averaged groundwater storages in this irrigation area and the core region of the West Lake Protected Area have the decrement of 2.62×10⁶ m³ and 9.99 ×10⁶ m³, respectively. Scenarios analysis based on the different amount of water transferring project, which are 0.8×10⁸ m³/a, 0.9×10⁸ m³/a, 1.0×10⁸ m³/a and 1.2×10⁸ m³/a, are carried out by using the established model, and the results indicate that groundwater levels are increased around 5.0～20.0 m in the Danghe alluvial fan and 7.0～15.0 m in the Crescent Moon Spring area after 50 years. However, groundwater levels in the West Lake Protected Area has a slow increase trend of 0.5 m in the predication period. Subsurface runoff is important and sustainable recharge sources in the West Lake Protected Area, but the water transferring project may improve the slow recovery groundwater levels in the West Lake Protected Area. The results of this study will provide important references for argument of the implement of the water transferring project.