Back to spillwaysSpillways & Outlets - Shaft spillways
The top of the shaft spillway
at Llyn Pontsticill in Wales
Shaft Spillway at Ladybower
Dam in England
When the reservoir level rises above the top of the spillway, the water flows over its sides and down into the shaft. At the bottom of the shaft, it enters a tunnel. The tunnel usually runs under the dam, and diverts the water to join the river downstream.