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The search for cleaner and greener sources of energy has led to the proliferation of small hydropower projects (SHPs), especially in tropical developing countries. These projects are widely propagated as environmentally benign due to the assumption that they have no emissions, negligible impacts on river flows, and smaller areas of submergence compared to those created behind large hydropower dams. However, there is a paucity of research examining the ecological impacts of SHPs, especially on tropical river systems.
This study assessed the reach- and catchment-scale impacts of SHPs in the Western Ghats landscape of India - a global biodiversity hotspot and a distinct freshwater ecoregion. For this study, we collected data from three streams - two dammed and one undammed - in a hierarchical framework to examine the effects of SHPs on water quality, channel geometry, and fish assemblages.
Subsequently, we assessed the catchment-scale impacts of SHPs in the Western Ghats of Karnataka State, where 81 SHPs have been commissioned, and over 350 more have been planned for further development. The spatial clustering and extent of SHP-related dewatering on the drainage network across the study site was estimated. This scenario was compared with the expected scenario of when all proposed SHPs would be commissioned to predict the full extent of impact to the drainage network.
Reach-level impacts were highly significant. SHP related operations reduced habitat availability by altering stream geometry and longitudinal connectivity, affected habitat quality by altering water quality parameters and thereby affected fish species richness. At the catchment-scale, the extent of dewatering was found to be substantial and spatially clustered. Based on existing and proposed scenarios, priority catchments were identified. In light of our findings, we suggest suitable changes to SHP operations and policies. |
