page_title: Spillway
section_title: Bell-mouth spillway
hierarchical_section_title: Spillway / Types / Bell-mouth spillway
caption_attribution_description: English: View of Hungry Horse Dam spillway in operation.
context_page_description: A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that the water does not overflow and damage or destroy the dam.
  Floodgates and fuse plugs may be designed into spillways to regulate water flow and reservoir level. Such a spillway can be used to regulate downstream flows – by releasing water in small amounts before the reservoir is full, operators can prevent sudden large releases that would happen if the dam were overtopped.
  Other uses of the term "spillway" include bypasses of dams or outlets of channels used during high water, and outlet channels carved through natural dams such as moraines.
  Water normally flows over a spillway only during flood periods – when the reservoir cannot hold the excess of water entering the reservoir over the amount used. In contrast, an intake tower is a structure used to release water on a regular basis for water supply, hydroelectricity generation, etc.
context_section_description: A bell-mouth spillway is designed like an inverted bell, where water can enter around the entire perimeter. These uncontrolled spillways are also called morning glory, (after the flower) or glory hole spillways. In areas where the surface of the reservoir may freeze, this type of spillway is normally fitted with ice-breaking arrangements to prevent the spillway from becoming ice-bound.
  In some cases, bell-mouth spillways are gate-controlled. The spillway at Hungry Horse Dam (pictured), in Montana, U.S., the highest morning glory structure in the world, is controlled by a 64-by-12-foot (19.5 by 3.7 m) ring gate. One of the most well-known of these spillways is the one in Covão dos Conchos reservoir lake, in Portugal, which is constructed to look like a natural formation; a video of this went viral on the Internet in early 2016. The largest bell-mouth spillway is in Geehi Dam, in New South Wales, Australia, measuring 105 ft (32 m) in diameter at the lake's surface.
caption: Bell-mouth spillway of Hungry Horse Dam in operation.
exif: {}