Sunday, November 21, 2010

Giant Hole in Dam Water!!

Giant Hole

At first glance you might mistake a bell-mouth spillway for a watery vortex into one more dimension. What can only be described as a giant hole in the water is actually a method for controlling the let go of flows from a dam or levee into a downstream area. These spillways help prevent floods from ‘dam’-aging or annihilate a dam.


A spillway is a structure used to provide for the controlled release of flows from a dam or levee into a downstream area, characteristically being the river that was dammed. Spillways release floods so that the water does not overtop and injure or even destroy the dam. Except during flood periods, water does not usually flow over a spillway. In contrast, an intake is a structure used to release water on a regular foundation for water supply, hydroelectricity generation, etc.
Floodgates and combine plugs may be designed into spillways to regulate water flow and dam height. Other uses of the term “spillway” include bypasses of dams or outlets of a channels used during highwater, and outlet channels imprinted through natural dams such as moraines.


Some spillways are intended like an inverted bell so that water can enter all around the perimeter. These uncontrolled spillway devices are also called: morning glory, plughole, glory hole, or bell-mouth spillways. In areas where the surface of the reservoir may freeze, bell-mouth spillways are normally fitted with ice-breaking arrangements to stop the spillway from becoming ice-bound.


Ladybower Reservoir is a large Y-shaped reservoir, the lowest of three in the Upper Derwent Valley in Derbyshire, England. The River Ashop flows into the reservoir from the west; the River Derwent flows south, initially through Howden Reservoir, then Derwent Reservoir, and finally through Ladybower Reservoir. Its longest dimension is just over 3 miles (5km), and at the time of construction it was the largest reservoir in Britain (1943)