基于水化学和同位素示踪岩溶含水系统的水力联系——以宜春市四方井副坝区为例

Tracing Hydraulic Connection of a Karst Aquifer System Based on Hydrochemistry and Isotopes:A Case Study of the Auxiliary Dam of Sifangjing in Yichun City

为查明宜春四方井水库副坝区地下水流系统的分布,指导副坝区地下工程注浆帷幕的设计与施工,采用现场盐示踪试验,结合水化学和同位素数据分析测试,揭示副坝区地下水与下游村庄(四方井)泉水的水力连通关系。结果表明:大气降水是地下水的补给来源,蒸发和水岩相互作用是控制地下水水化学形成的关键因素;地下水和地表水的水化学类型主要为HCO_(3)-Ca,沿着地下水径流的途径,地下水的矿化度(total dissolved solids,TDS)呈现增加的趋势,表征副坝区地下水与其下游四方井村的泉点间具有潜在的水力联系;现场盐示踪试验和δD、δ^(18)O分布的研究,进一步验证了副坝区地下水与四方井的泉水点SD-3、SD-4和SD-7的水力联系较好,与泉点SD-5的连通性较弱,SD-5主要来自径流路径较短的上游水补给。研究结果有助于建立局部地下水流循环模式,查明地下水流系统的分布规律,为地下水资源的可持续开发利用及生态环境保护提供技术支撑和参考依据。

In order to study the distribution of a Karst groundwater flow system in the auxiliary dam area of Sifangjing reservoir in the Yichun,and to provide guidance for the design and construction of underground grouting curtain engineering in the dam area,an in-situ tracer test was performed in combination of hydrochemical surveys to reveal the hydrological connectivity between Karst aquifers of the auxiliary dam area and springs of a downgradient village(Sifangjing).The results show that the meteoric water is the origin of groundwater.Evaporation and water-rock interactions are important factors controlling the formation of groundwater constituents.Both groundwater and surface water are of HCO_(3)-Ca type.Along a groundwater flow path,total dissolved solids(TDS)values generally increased,indicating a potential connectivity between the auxiliary dam groundwater and spring waters in the Sifangjing Village.Results of tracer test and distributions ofδD andδ^(18)O further support that a good connection occurrs between the auxiliary dam groundwater and spring waters in monitoring sites SD-3,SD-4 and SD-7,while for spring SD-5,which is located farther from the auxiliary dam as compared to SD-3,SD-4 and SD-7,has a poor connection to the auxiliary dam groundwater and its water might come from the upgradient replenishment area with a short recharge pathway.Results are helpful to establish a local groundwater circulation model and to find out groundwater distribution pattens,and to provide technical supports and guidance for sustainable development and utilization of groundwater resources and ecological environment protection.