How does a dam release water?

Answer 1

A dam releases water through a controlled structure called a spillway or outlet works. The spillway is designed to safely discharge excess water from the reservoir to prevent overtopping of the dam and potential flooding downstream. The water is released either through gates that can be opened or closed as needed, or through a series of valves or pipes that control the flow rate. The release of water is carefully managed to balance the needs of flood control, water supply, and power generation.

Answer 2

Any modern dam has computer-controlled Gates which can be opened remotly by some switch/computer instruction .

+++

All dams have had release valves, or "sluices", built into them, irrespective of the mode of control. They are used to maintain flow in the river downstream during short dry spells, to flush out accumulated silt or to drain the reservoir for repairs.