Impact analysis of small hydropower construction on river connectivity on the upper reaches of the great rivers in the Tibetan Plateau

Abstract Hydropower construction may alleviate regional power shortages, regulate river water volume, improve energy structure. However, extensive hydropower construction activities can reduce the river connectivity, which will further lead to biodiversity loss and ecological environment degradation. Most impact assessments of river connectivity have concentrated on large hydropower stations, while few on small ones. Through field investigation, this study identified 236 small hydropower stations on the upper reaches of the great rivers in the Tibetan Plateau, including the Yellow and Yangtze Rivers. The authors established a river connectivity impact index (RCII) model to achieve quantitative analysis of the connectivity of each river segment. Four pressure indicators, the Degree of Fragmentation (DOF), the Degree of Flow Utilization (DFU), the Degree of Obstruction (DOO), and the Density of Road (DOR), were set up based on the station’s attribute data. The results indicate that the RCII can better express the impact degree of river connectivity with a high correlation coefficient R2 between the degree of water reduction and the RCII. More than 40.33% of the river reaches were with "heavy" RCII values, indicating that the construction of small hydropower stations had some impacts on river connectivity to some extent. Also, we found that DOF and DOR had greater impacts on river connectivity in the study area. The river connectivity impact had great spatial differences, with rivers in the eastern region being the most serious. Furthermore, the greater the damage of river connectivity, the greater the potential for loss of aquatic biodiversity. A framework was set up in our work to quantitatively evaluate the impact of small hydropower station construction on river connectivity, providing strong support for the further ecological river protection and strategic planning.