What are the environmental and socio-economic impacts and associated mitigation measures of small and pumped storage hydropower? A Systematic Review Protocol

The authors published their intended review overview, methodology, and more to answer their research question: What are the environmental and socio-economic impacts and associated mitigation measures of small and pumped storage hydropower? Small hydropower plants, defined in this review as installations with the capacity of ≤10MW, are widely deployed globally for decentralized electricity generation, including in remote and rural areas with limited or unreliable grid access. Pumped storage hydropower, by contrast, serves a different function as a widely deployed form of grid-scale energy storage and is increasingly important for energy system flexibility, grid stabilization and the integration of variable renewable energy sources (including wind and solar).

Despite their importance, the positive and negative impacts of small and pumped storage hydropower remain unevenly synthesized. Existing reviews tend to focus on specific regions or very specific outcome domains (e.g. biodiversity), resulting in a fragmented evidence base. Comprehensive global reviews that consider a broader set of outcomes including social, cultural, economic, and energy system dimensions, as well as cumulative impacts, are limited. Apart from operation or maintenance, there is a lack of syntheses of impacts across the full hydropower project cycle, including planning, construction, decommissioning and removal (but see paper for references). This fragmentation limits the ability of policymakers to make informed decisions regarding planning, deployment, maintenance, decommissioning and mitigation of small and pumped storage hydropower projects.

Given these synthesis gaps, this review aims to: (1) systematically map the existing evidence on reported positive and negative impacts and associated mitigation measures of small and pumped storage hydropower installations, and (2) synthesize evidence on selected impacts and/or mitigation measures based on literature
availability and policy relevance. A meta-analysis will be considered if, following the initial evidence mapping and stakeholder prioritization process, the selected review question is suitable for quantitative synthesis. While not designed as a comparative synthesis, the review includes both technologies, small and pumped storage hydropower, due to their distinct but complementary roles in the energy systems.