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Different types of spillways are as follows:, 1. Straight Drop Spillway, 2. Ogee Spillway, 3. Shaft Spillway, 4. Trough Spillway, 5. Side Channel Spillway, 6. Siphon Spillway, 1. Straight Drop Spillway, A Straight drop spillway consists of low height weir wall having its downstream face roughly or perfectly vertical., When the water level in the reservoir rises above the normal pool level, the surplus water falls freely from the, crest of the weir and hence it is known as Straight drop spillway or free overfall., Straight drop spillways are most suitable for thin arch dams, earthen dams., , 2. Ogee Spillway, Ogee spillway, as the name says, represents the shape of the downstream face of the weir. It is an improved, form of a straight drop spillway. In this case, the downstream face of the weir is constructed corresponding to, the shape of lower nappe of freely falling water jet which is in ogee shape., Ogee spillways are most commonly used in case of gravity dams, arch dams, buttress dams, etc. For gravity, dams, it is generally located within the dam body.

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3. Shaft Spillway, A Shaft spillway is a type of spillway which consists of a vertical shaft followed by a horizontal conduit. The, surplus water enters into the vertical shaft and then to the horizontal conduit and finally reaches the, downstream of the channel., Shaft spillway is recommended when there is no space to provide for other types of spillways such as ogee, spillway, straight drop spillway, etc., , 4. Trough Spillway, It is a type of spillway in which surplus water from upstream is disposed to the downstream through a steeply, sloped open channel. It is generally constructed at one end of the dam or separately away from the dam in a, natural saddle in a bank of the river., The slope of trough spillway is designed in such a way that the flow should be always in supercritical condition., , 5. Side Channel Spillway, Side channel spillway is similar to chute spillway but the only difference is the crest of side channel spillway is, located on one of its sides whereas crest of chute spillway is located between the side walls.

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6. Siphon Spillway, A siphon spillway is a type of spillway in which surplus water is disposed to downstream through an inverted U, shaped conduit. It is generally arranged inside the body or over the crest of the dam., In both types of siphon spillways, air vents are provided at the bent portion of the upper passageway to prevent, the entrance of water when the water level is below the normal poll level. Whenever the level rises above, normal pool level, water enters into the conduit and is discharged to the downstream of the channel by siphonic, action.