Spatial variability of lacustrine groundwater discharge at basin scale

Lacustrine groundwater discharge (LGD) is a crucial component of water balance in lakes. However, research on the spatial variability of LGD on a large basin scale is scarce, and the factors controlling this variability are not well understood. In this study, we examined various lakes located throughout the CYRB using multiple tracers and field surveys to determine the occurrence of LGD. We employed a ²²²Rn mass balance model to determine LGD rates in various lakes within the central Yangtze River basin (CYRB). Additionally, we identified the factors controlling the spatial variability of the LGD rates using correlation analysis and a multiple linear regression model. Our findings revealed that while the ²²²Rn concentration in groundwater (6082.27 ± 3860.16 Bq/m³) was within the global average, the concentration in lake water (306.97 ± 239.45 Bq/m³) was relatively high, indicating a stronger LGD in the CYRB. The stable isotopes, ²²²Rn concentration, and the groundwater seepage and springs, collectively confirm the occurrence of LGD. The LGD rates in lakes within the CYRB area exhibited significant spatial variability, ranging from 13.76 to 83.96 mm/d, with larger LGD rates found at the interior of the basin than at the edges. Hydrological connectivity, location within basin, and lake water depth collectively control the LGD rate, with each contributing 53.95%, 22.90%, and 23.16%, respectively. This study not only enriches our understanding of LGD, serving as a reference for global research on LGD, but also provides theoretical guidance for local water resource management.