The future of hydroelectric power is shifting away from massive new mega-dam construction toward modernization, efficiency upgrades, and small-scale or pumped-storage hydroelectric projects. As global power grids integrate higher percentages of intermittent solar and wind energy, existing hydropower facilities will play a vital role in providing grid stabilization and energy storage through pumped-storage systems. Furthermore, digitalization, environmental remediation, and fish-friendly turbine designs will shape sustainable hydro development.