Response characteristics of vegetation net primary production to cascade hydropower development and climate change in the dry-hot valleys of the Jinsha River

The dry-hot valley of the Jinsha River, Southwestern China This study aims to quantify the ecological impacts of cascade hydropower development on Net Primary Production (NPP) in this fragile region. To achieve this, we developed a non-reservoir scenario simulation framework. This approach integrates the Pettitt mutation test with a Long Short-Term Memory (LSTM) model to effectively isolate the effects of reservoir operations from those of background climate change. The operation of cascade reservoirs has reshaped the region's local hydrology and climate, leading to complex ecological outcomes. We found that reservoir impoundment led to increased air temperature, precipitation, and soil moisture, coupled with a decrease in land surface temperature. The change in hydrological and climatic conditions has resulted in an overall increase of approximately 12 % in NPP compared to pre development levels. During the dry season, the reservoirs alleviate water stress, causing significantly greater NPP growth than in the rainy season. Conversely, during the rainy season, the reservoirs' primary influence shifts to intensifying heat-related factors. Temperature was identified as the single most dominant, non-linear driver of these vegetation changes. This study provides insights into the ecological impacts of hydropower development and the interactions between hydropower operations, climate factors, and vegetation dynamics in dry-hot valley ecosystems. • A novel simulation isolates hydropower's true impacts on NPP from climate change. • NPP declined during the construction but increased by about 12 % after impoundment. • Post-impoundment NPP growth is higher in the dry season than the rainy season. • Impoundment altered the local climate: TMP and SMCI rise, LST falls. • Dams’ seasonal roles: easing dry season water stress, boosting rainy season heat.