Weir
A weir is a barrier built across a river which changes the flow of the river, usualy for irrigation and smaller than a dam. Depending on the design, some pose problems for fish, as the fish cannot get across the weir.
Gallery
Many fish have the capability to jump over weirs. This shows a salmon
this kind of weir is difficult for fish to climb
Weir designed to make it easy for fish to climb
Weir Media
A weir on the Yass River, New South Wales, Australia, directly upstream from a shared pedestrian-bicycle river crossing
A weir on the Tikkurilankoski rapids in Vantaa, Finland
Time-lapse video of a new tilting weir being installed in the Caldicot and Wentloog Levels
The broad crested weir at the Thorp grist mill in Thorp, Washington, US
Water flowing over a spillway at Hoover Dam in Arizona, USA, during the 1983 floods
During periods of high river flow, this nineteenth century weir of porphyry stone on a creek in the Alps would have significantly more water flowing over it.
The bridge and weir mechanism at Sturminster Newton on the River Stour, Dorset, UK
Two weirs on the River Wear in Durham, UK: the lower weir is a compound weir that also has fish ladders to allow fish such as salmon to navigate the weir
