拉萨河流域中下游地区水化学及地表水-地下水转化关系研究

Hydrochemistry and relationship between groundwater and surface water in the middle and lower reaches of Lhasa river basin

为研究拉萨河流域中下游地区水化学及地表水地下水转化关系,利用水化学资料分析了不同水体水化学和稳定同位素特征,并探讨了地表水-地下水之间的转化关系。结果表明:拉萨河流域中下游地区不同水体中主要离子含量均较低,矿化度较低,呈弱碱性,水化学类型均以HCO3·SO4(SO4·HCO3)-Ca·Mg(Mg·Ca)型为主。不同水体的水化学组成主要受岩石风化作用控制,且以碳酸盐岩和硅酸盐岩的溶解风化为主。水化学及同位素分析表明:水样点可分为地表水、地下水以及混合区三个区域,说明研究区地表水和地下水水力联系密切,存在明显的转化关系;地表水、地下水、泉水的主要来源均为大气降水,不同水体均受到不同程度的蒸发作用影响;支流地表水主要受地下水补给,拉萨河中下游地表水和地下水存在地段性互补关系,拉萨河是区域地下水的主要排泄通道。

In order to study the hydrochemistry and relationship between groundwater and surface water in the middle and lower reaches of Lhasa river basin,the hydrochemistry and stable isotope characteristics of different water bodies in the study area were analyzed by using hydrochemical data,and the transformation relationship between surface water and groundwater was also discussed.The results show that the main ions in different water bodies in the middle and lower reaches of the Lhasa river are relatively low,with low salinity and weak alkalinity,and the main hydrochemical types are HCO3·SO4(SO4·HCO3)-Ca·Mg(Mg·Ca).The hydrochemical compositions of different water bodies are mainly controlled by rock weathering,mainly by dissolution and weathering of carbonate and silicate.Hydrochemistry and isotope analysis indicate that the water sample points can be divided into three areas:surface water,groundwater and mixed area,suggesting that the surface water and groundwater in the study area are closely related and have obvious transformation relationship.The recharge sources of surface water,groundwater and spring water are atmospheric precipitation and different water bodies have been evaporated to varying degrees.The main tributary surface water is mainly recharged by groundwater.The surface water and groundwater in the middle and lower reaches of the Lhasa river complement each other and the Lhasa river is the main drainage channel for regional groundwater.