Concentration of rainfall into artificial lakes to generate power was already done centuries ago: https://www.banskastiavnica.travel/en/what-to-see/stiavnicke-

Concentration of rainfall into artificial lakes to generate power was already done centuries ago: https://www.banskastiavnica.travel/en/what-to-see/stiavnicke-tajchy/ https://www.banskastiavnica.travel/en/what-to-see/stiavnicke... The mine drainage system was later gradually replaced with steam engines, however there is a ~megawatt hydropower electrical plant still functional.