Geograph - photograph every grid square

The barrage was constructed in 1992 to allow a mid-tidal depth within the river at all times, becoming the first tidal barrage across a river in the UK. However within two years the National Rivers Authority had found serious problems with oxygen levels in the river and ability of migratory fish, such as salmon, to find gaps in the fish pass. Improvements were needed and successful modifications to the barrage fish pass were completed in the year 2000; a system has also been developed to prevent over-salination resulting from the incursion of sea water at high tide.