甘肃北山-河西走廊-祁连山区域地下水循环模式

山区地下水流动受到区域气候条件、地形地貌、地质构造等因素共同控制，限于资料有限，其流动模式与控制机理尚不清晰。特别是地处甘肃北山的高放废物地质处置库预选区、河西走廊以及祁连山北麓区域地下水的流动模式，直接决定了处置库在万年时间尺度上的安全性。基于区域遥感构造解译、地质构造演化分析、地球物理勘探以及水文地质钻探，获取了典型剖面的水文地质结构与渗透特征；综合区域水文地质调查、水文地球化学与同位素特征数据，构建了甘肃北山-河西走廊-祁连山山区的水文循环概念模型；并通过构建区域地下水流动数值模型与多情景模拟，分析了甘肃北山-河西走廊-祁连山山区的地下水流动模式。结果表明，地形对于该地区的地下水流动模式具有主控作用，祁连山山区地下水难以越过海拔最低的河西走廊至北山山区排泄，河西走廊是祁连山山区地下水系统与北山山区地下水系统的边界；北山山区地下水在地形与岩性的控制下，仅发育局部流动系统且渗流速度缓慢。同时由于该地区地质构造的阻滞作用，北山新场地下水无法径直向南穿越构造向花海盆地排泄，渗流路径长度明显增加；仅有F₉₅断裂构造以南山前地带地下水可向花海盆地排泄，但由于集水流域有限、渗流速度缓慢、循环交替能力差，排泄量较小。本研究探究了山区-盆地地下水循环模式，为高放废物地质处置库候选场址的适宜性评价提供了科学依据。 

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

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.