洞庭湖区水系发达,水文地质条件复杂,人类活动强烈,地表水和地下水的水力联系变化频繁,其研究的难度以及由此造成的研究不足影响了对湖区地下水赋存和运动规律的深入认识。本文以洞庭湖整体为研究对象,采用水位动态分析和氡(²²²Rn)同位素示踪法,定性和定量研究枯水期洞庭湖区地表水与地下水的交互作用关系与交互通量。枯水期洞庭湖区水位和氡浓度空间分布特征指示研究区内地下水向湖水排泄,尤以东洞庭湖最为显著。氡箱模型计算结果显示枯水期地下水排泄²²²Rn通量为455.09 Bq/(m²·d),占总输入²²²Rn通量的60.07%,地下水排泄总量为0.29×10⁸ m³/d,平均排泄速率为56.27 mm/d,地下水排泄对湖水的贡献率为7.04%。敏感性分析表明:风速、地下水和湖水²²²Rn浓度以及湖面面积等参数较为敏感,合理布置取样点并提高敏感参数测量准确度能提高模型计算结果的可靠度。氡同位素示踪法物理意义明确、操作过程简便,是研究复杂区域地下水补、径、排特征的有效方法。研究成果一定程度上提供了洞庭湖区水量均衡的更多认识,可为洞庭湖区地下水资源评价和管理提供参考。

Lake Tongting area has a dynamic water environment with developed surface water networks, complex hydrogeological conditions and intensive human activities, which makes it difficult to gain in-depth understanding of groundwater storage and movement in the lake area. This study applies dynamic analysis of water levels and radon (²²²Rn) tracer method to carry out qualitative and quantitative analyses of surface water-groundwater interaction and exchange fluxes in Lake Tongting area in the dry season. The spatial distribution patterns of water levels and ²²²Rn concentrations in the lake area in the dry season (between 2018-2020) indicated that groundwater (GD) discharge to the lake occurred in the dry season, especially in eastern Lake Dongting. According to calculation using radon box model, the GD-borne ²²²Rn flux in the dry season was 455.09 Bq/(m²·d), or 60.07% of total ²²²Rn flux to the lake; the total groundwater discharge was 0.29×10⁸ m³/d, and the average discharge rate was 56.27 mm/d. Groundwater discharge contributed to 7.04% of surface water in the dry season. Sensitivity analysis showed that sensitive variables in the model were wind speed, ²²²Rn concentration in groundwater/lake water and surface area. Improvements of sampling scheme and measurement accuracy of sensitive variables can improve reliability of calculation results. With clear physical significance and simple application protocol, radon (²²²Rn) tracer has certain application advantageous that it can be effectively used to quantify groundwater recharge, runoff and discharge in complex water environments. The research results provide better understanding of water balance in Lake Dongting and can serve as reference for water resource evaluation and management in the lake area.