Spatial-seasonal variability of hydrochemistry and lake water-groundwater interaction in the Poyang Lake Basin, China

Abstract Extreme climatic events pose challenges to the sustainability of water resources and aquatic ecosystems in the Poyang Lake Basin. To reveal hydrochemical characteristics and lake-groundwater interactions under extreme conditions, 36 water samples were collected in July 2021 (flood season) and July 2022 (drought season), using hydrochemical statistics, correlation analysis, and isotopic techniques. The results show that lake water recharges groundwater during the flood season: ions are derived from the weathering of carbonate, evaporite, and silicate rocks, as well as from soil leaching, with nitrate nitrogen mainly originating from sewage and manure (accounting for the highest proportion). In contrast, groundwater recharges lake water during the drought season: ions are primarily derived from the dissolution of sedimentary and silicate rocks, which are significantly affected by intense surface evaporation. Ion sources during both periods are regulated by leaching, weathering, evaporation, and human activities, with weak ion exchange. The established hydrochemical model interprets seasonal hydrochemical distinctions and provids scientific support for lake aquatic ecological research and basin water resource management.