A hydropower station in which all or most of the generating water is concentrated by water-retaining structures on the river.

Dam-type hydropower stations mainly refer to hydropower stations that build water-retaining structures on the river to form a reservoir, concentrate natural water to raise the water level, and use the head difference to generate electricity. The main feature is that the dam and the hydropower plant are concentrated in the same short river section.
Dam-type hydropower stations generally include water-retaining structures, water-discharging structures, pressure pipes, power plants, turbines, generators and ancillary equipment. Most of the hydropower stations with dams as water-retaining structures are medium-high head hydropower stations, and most of the hydropower stations with gates as water-retaining structures are low head hydropower stations. When the water head is not high and the river is wide, the power plant is often used as part of the water-retaining structure. This type of hydropower station is also called a riverbed hydropower station, which is also a dam-type hydropower station.
According to the relative position of the dam and the hydropower plant, dam-type hydropower stations can be divided into two categories: dam-type and riverbed. The dam-type hydropower plant is arranged on the downstream side of the dam body, and water is diverted through the pressure pipe to generate electricity. The plant itself does not bear the upstream water pressure. The powerhouse, dam, spillway and other buildings of riverbed hydropower station are all built in the riverbed. They are part of the water retaining structure and bear the upstream water pressure. Such an arrangement is conducive to saving the total investment of the project.

The dam of the dam-behind hydropower station is usually high. First, the high head is used to increase the installed capacity of the power station, which can effectively adapt to the peak regulation requirements of the power system; second, there is a large reservoir capacity to regulate the peak flow to reduce the flood control pressure of the downstream river; third, the comprehensive benefits are more significant. The disadvantage is that the flooding loss in the reservoir area increases and the relocation and resettlement of urban and rural residents are difficult. Therefore, the dam-behind hydropower stations with high dams and large reservoirs are mostly built in high mountain valleys, areas with large water inflow and small flooding.
Most of the huge dam-behind hydropower stations built in the world are concentrated in my country. The first one is the Three Gorges Hydropower Station, with a total installed capacity of 22.5 million kilowatts. In addition to the huge power generation benefits, the Three Gorges Hydropower Station also has the comprehensive benefits of ensuring flood control in the middle and lower reaches of the Yangtze River, improving navigation and water resource utilization, and is called “the country’s heavy equipment.”