Study on the impact of dam construction and interception on spatiotemporal changes in vegetation coverage in cascade reservoirs: Wujiang and Chishuihe catchments

A series of cascade hydropower stations have been built in the Wujiang catchment in recent years. Here, we studied the sustainability of past and future changes in vegetation coverage and the scale of dam construction impact using MODIS normalized difference vegetation index (NDVI) time series data, Sen trend analysis, and Hurst index taking Wujiang (dam constructed) and Chishuihe (no dam construction) as examples. Results indicated that: (1) the NDVI in the Wujiang and Chishuihe catchments showed a fluctuating upward trend, and the main variation type increased significantly. (2) On the spatial scale, vegetation coverage in the middle and lower reaches of the Wujiang catchment decreased. (3) Future trends in vegetation coverage differed for the Wujiang and Chishuihe catchments. Average Hurst index of the Wujiang catchment was less than 0.5, indicating relatively strong anti-sustainability of vegetation coverage change, especially in the middle and lower reaches of the catchment. Average Hurst index of the Chishuihe catchment was greater than 0.5, indicating strong sustainability of vegetation coverage change. Thus, dam construction has influenced vegetation coverage around the river in the past and will sustainably influence future vegetation coverage variation.