Irrigation Engineering Practice Test: Spillways, Energy Dissipators and Spillway Gates — Flashcards

Spillways are hydraulic structures that divert excess water from a reservoir after it has reached its maximum capacity. Energy dissipators are structures that reduce the energy of water flow after it passes through a spillway. 

Here are some types of spillways:
Chute spillway: A spillway that carries surplus water from upstream to downstream through a steeply sloped open channel. It's usually built at the end of a dam or separately in a natural saddle in the riverbank. Chute spillways are useful for gully head control and can be used for drops of up to 5–6 meters.
Ogee spillway: Allows for uncontrolled flow over the top of the reservoir. The discharge coefficient in the weir flow equation is automatically adjusted when the upstream energy head is above or below the design head.
Side channel spillway: The flow in this spillway is turned 90° after passing the crest so that the flow is parallel to the weir crest. It's best suited for non-rigid dams like earthen dams. 

Energy dissipators can be internal dissipators, stilling basins, and streambed level dissipators. 
Spillways should be located so that water can be disposed of safely without toe erosion. They should also release surplus water safely and in a regulated manner.