What does spillway mean?
A spillway is a channel or opening that allows water to escape from a reservoir, dam, or similar structure. It is commonly used to manage water levels by diverting excess water, especially during heavy rainfall or floods, and is often fitted with gates or other control mechanisms. The word is most common in engineering and water-management contexts but is readily understood by general audiences. A spillway differs from a weir: the former provides an outlet for water to flow, while a weir is a barrier used to raise or regulate the level of water in a river or channel. Spillways are important safety infrastructure because they help prevent a dam from being overtopped and damaged.
nounA channel, passage, or opening through which water is discharged from a reservoir, dam, or other structure when it exceeds the normal level. It may also be designed to release water deliberately.
- A channel or opening for the discharge of water from a reservoir, dam, or similar structure.
- A structure or passage designed to carry excess water safely away.
"Heavy rainfall forced the reservoir to release excess water through the spillway."
"Engineers opened the spillway as the reservoir approached its maximum capacity."
"The old stone spillway carries floodwater from the lake into the river below."
The regular plural is used when referring to multiple spillways or to the several components of a dam system.
"The hydroelectric station has two spillways for releasing excess water."
A spillway is a dam’s emergency escape route, preventing rising water from overtopping the structure.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does spillway come from?
The word is a compound of “spill” and “way,” literally suggesting a way for water to spill or escape. The term developed in the language of hydraulic engineering as structures for controlled water discharge became increasingly important. The idea of a spill channel is older than the modern compound, but “spillway” is the established modern term for the discharge route associated with a reservoir or dam.
Related word forms
How spillway is actually used
The term is primarily used in civil engineering, hydrology, and water management. It can refer to the entire channel or structure, though it more specifically denotes the route through which water is released.
Easily confused with spillway
A weir is a low barrier built across a watercourse to raise or regulate its level, whereas a spillway is a passage for water to escape from a reservoir or dam.