Variation of lake-river-aquifer interactions induced by human activity and climatic condition in Poyang Lake Basin, China.

• Impact from hydrological change was overwhelming relative to climate factors. • Dry season advanced by one month due to the impoundment in TGD. • Bank storage is meant to block the discharge from alluvial aquifer to river. • Recovery of the groundwater storage deficit would be harder than the surface water. In low-lying fluvial-lacustrine plain, anthropogenic activities and climatic variation could have a comprehensive influence on the interactions between surface water and groundwater (SW-GW) involving lake-river-aquifer. Quantification of the changes in SW-GW interaction in spatial and temporal scale causing by the two driving sources could help to the understanding of the regional water cycle mechanism and the adjustment of the decision making. However, it is usually difficult to distinguish the impact of anthropogenic activities from the climatic variation on a regional scale. Here, by using a regional three-dimensional groundwater numerical model with long term monitoring of the hydrological dynamic in Poyang Lake Basin (PLB), China, we found that groundwater storage variation in the bank storage districts can be used as an indicator to quantify each source and sink in the process of SW-GW interactions. And surface water infiltration plays a more dominant role in constructing bank storage which is meant to preserve groundwater storage. Our research in PLB demonstrates that the hydrological change caused by the operation of the Three Gorges Dam (TGD) since 2003 is mainly responsible for the autumn drought in PLB. The surface water recession due to the impoundment in TGD from September to October has an impact about 7 times stronger than the rainfall reduction. Moreover, the groundwater storage deficit caused by the insufficient recharge from the surface water infiltration would maintain the whole year, unlike the surface water system which would easily recover at the end of the year. The results demonstrate the chain interactions among lake-river-aquifer. Failing to distinguish the magnitude of each influence factor may lead to underestimating the impact on the whole water system. The results also highlight the function and the vulnerability of the groundwater system which might be vital to the riparian and estuarine-wetland ecosystem. [ABSTRACT FROM AUTHOR]