What are the necessary conditions for the production of hydroelectric energy?

Hydroelectric power generation must meet at least two conditions: First, there must be a huge gap. In rivers with high specific fall rates, narrow valleys in rivers or the use of high artificial dams, large falls can occur, resulting in strong downward momentum and horizontal flow velocity. Second, there must be huge traffic. A river with only height difference and without significant flow cannot form strong hydraulic power. Therefore, the flow rate plus the height difference is the main basis for determining whether hydraulic power is abundant. The water drop we use here actually uses the gravitational energy of the water.