Analysis of driving forces on ecohydrological regime and environmental flow changes in Hongze Lake, China

This is the authors' abstract. We don't add key points for this paper.

Environmental flow refers to the fundamental hydrological process that sustains the ecosystem of rivers and lakes. Safeguarding environmental flow is crucial for optimal water resource utilization and lake ecosystem preservation. The study delivers a comprehensive exploration of ecohydrology, focusing on the common analysis of runoff and water level (RWL) to evaluate ecohydrological conditions in Hongze Lake (HZL) over five decades (1970–2020). Techniques such as the change point test and wavelet analysis were employed to discern trends and periodicity in hydrological elements. A series of ecologically pertinent indicators was applied to measure the changes in RWL, assessing their impacts on the lake's ecosystem. The Budyko hypothesis and cumulative slope rate of change (CSRC) were integrated for a quantitative analysis that shed light on the ecological response to RWL variations. Differential effects of human activities and climate change on runoff were discerned through subsurface parameter analysis across different decades. The study's results indicate that human activities, particularly gate dam operations and agricultural irrigation, have precipitated a significant reduction in environmental flow components (EFCs). The gate dam manipulation during the dry season has notably influenced the lake's hydrological regime, with a substantial alteration of RWL by 37% and 41%, respectively. This hydrological modification aligns with observed ecological trends such as species population reduction, habitat fragmentation, and organism miniaturization within HZL. Analysis of subsurface parameters also reflected an increasing influence of climatic factors on runoff over time. Human activities, evapotranspiration, and precipitation were found to contribute 75.5%, 10.3%, and 14.2% to runoff alterations, and 70.1%, 11.4%, and 18.5% to water level (WL) changes, respectively.