Environmental Impact Assessment of Hydropower: A Systematic Review of Common Criteria, Dynamic Nature of Criteria, and Emerging Properties

Hydropower has emerged as a critical component of clean energy initiatives worldwide, providing substantial contributions to electricity generation and grid stability. However, the construction and operation of hydropower dams also pose significant environmental and socio-economic challenges, including habitat fragmentation, water quality fluctuations, and community displacement. Environmental Impact Assessment (EIA) offers a structured framework to evaluate these potential impacts and inform mitigation strategies. Yet existing EIAs often overlook two pivotal dimensions: the dynamic nature of certain criteria and the emergent properties of hydropower as a complex system. This paper addresses these gaps through a systematic review of scholarly articles published between 2000 and 2024, examining current practices in hydropower EIAs and identifying overlooked criteria. Our findings indicate that standard EIAs tend to prioritize static parameters while underrepresenting temporal variability in key biophysical and socio-economic processes (e.g., water temperature, sediment transport, and socio-economic change). Moreover, EIAs typically pay limited attention to emergent system-level outcomes, including changes in local microclimate and community cohesion, which may develop nonlinearly and with substantial uncertainty after dam commissioning. We proposed an analytical framework that classifies EIA criteria into static and dynamic, alongside recommendations for integrating emergent complexities. This includes adaptive management practices, real-time monitoring to capture evolving conditions, and greater stakeholder engagement to address social implications. By explicitly accounting for temporal dynamics and emergent effects in hydropower systems, the proposed EIA framework strengthens impact assessment by improving the characterization of risks and trade-offs, thereby informing more sustainable and equitable hydropower development.