作者：Du, Y., Sun, X., Xu, J., Shi, H., Tian, H., Han, P., Deng, Y., Gan, Y. & Wang, Y.

Lacustrine groundwater discharge (LGD) plays a key role in lake hydrology and nutrient dynamics but is often overlooked. While previous studies have quantified LGD and nutrient fluxes in individual lakes under natural conditions, the influence of human-altered hydrological conditions across multiple lakes remains unclear. To address this, we studied four oxbow lakes with similar climate, geomorphology, and geology but differing hydrologic connectivity to the Yangtze River, which resulted in distinct seasonal water-level fluctuations. Using a 222Rn mass balance model along with hydrological, hydrochemical, and nutrient data, we quantified LGD and associated nutrient fluxes. Lakes naturally connected to the Yangtze River exhibited larger seasonal water-level fluctuations and higher LGD and nutrient fluxes than sluice-isolated lakes with more stable water levels. Lakes naturally connected to the Yangtze River exhibited larger seasonal water-level fluctuations and higher LGD and nutrient fluxes than sluice-isolated lakes with more stable water levels. This phenomenon can be attributed to greater groundwater storage from lake water recharge during the wet season and larger hydraulic gradient between groundwater and lake water due to lake water outflow during the dry season. As a result, the higher LGD-associated nutrient fluxes contributed to a higher nutrient status within the lakes. This study revealed the regulatory role of hydrologic connectivity on the lake nutrient status by altering water level fluctuations between wet and dry periods, which in turn affects LGD. This provides a new perspective for improving our understanding of nutrient dynamics in lakes that highly rely on groundwater contributions.

湖泊地下水排泄（LGD）在湖泊水文与营养盐动态中发挥着关键作用，但常被忽视。既往研究多在自然条件下对单一湖泊的LGD及其营养盐通量进行定量，而人为改变的水文条件在多个湖泊中的影响仍不清楚。研究选取4个气候、地貌与地质条件相似、但与长江水力连通性不同的牛轭湖——不同的连通性导致了各自独特的季节性水位波动。利用²²²Rn质量平衡模型，结合水文、水化学与营养盐数据，我们定量了LGD及其伴生的营养盐通量。结果表明：与长江自然连通的湖泊，其季节性水位波动幅度更大，LGD与营养盐通量也高于受水闸阻隔、水位较为稳定的湖泊。这一现象可归因于：汛期湖水补给地下水使地下水储量增大，枯水期湖水外泄使地下水与湖水间的水力梯度增大。由此，较高的LGD伴生营养盐通量导致这些湖泊的营养状态更高。本研究揭示了水力连通性通过改变丰水期与枯水期之间的水位波动、进而影响LGD，对湖泊营养状态所起的调节作用，为深化认识高度依赖地下水贡献的湖泊营养盐动态提供了新的视角。

（来源：Journal of Hydrology 2026  DOI: 10.1016/j.jhydrol.2026.135172）