Regional groundwater flow pattern in Beishan, Hexi Corridor and Qilian Mountain

Abstract

Groundwater flow in mountainous areas is controlled by climate conditions, topography, geological structure, and other factors.Due to the restrictions such as data acquisition, the groundwater flow pattern and control mechanism in mountainous areas are still not clearly understood.Taking Beishan area as an example, which locates the pre-selected area of the Geological Repository for High-Level radioactive Waste in China, groundwater flow pattern is of great significance for the safety of the repository on the ten-thousand-year time scale.In this study, characteristics of the hydrogeological structure and permeability in Beishan area, Hexi Corridor, and Qilian Mountains were obtained based on regional remote sensing interpretation, geological structure evolution analysis, geophysical exploration, and hydrogeological drilling.A conceptual model was proposed through comprehensive hydrogeological survey, hydrogeochemical and isotope analysis.In addition, regional groundwater flow numerical models and multi-scenario simulations were used to understand the groundwater flow patterns in the Beishan-Hexi Corridor-Qilian Mountains in Gansu.Results show that topography plays a dominant role in the groundwater flow pattern in the area.Groundwater from Qilian Mountains is difficult to pass through the Hexi Corridor to discharge in the Beishan Mountains.With the lowest altitude in the region, the Hexi Corridor can be regarded as the boundary of the groundwater system between the Qilian Mountains and the Beishan Mountain.Under the control of topography and lithology, the groundwater in Beishan mountain area only develops local flow systems and the flow velocity is small.At the same time, due to the blocking effect of the faults in this area, the groundwater from Xinchang, the key pre-selected high level radioactive waste disposal site in Beishan, cannot flow directly to the south into the Huahai Basin.In addition, its length of the flow path is greatly increased.Only the groundwater on the south side of the F95 fault can discharge to the Huahai Basin, but due to the limited catchment basin, slow flow velocity and poor circulation condition, the discharge is weak.This study investigates the mountain-basin groundwater circulation pattern, and provides a scientific basis for the site evaluation of the geological repository for high-level radioactive waste in Beishan, Gansu