The Swansea barrage (or the Tawe barrage) was completed in 1992 creating a new marina at the mouth of the

River Tawe The River Tawe (; cy, Afon Tawe ) is a long river in South Wales. Its headwaters flow initially east from its source below Llyn y Fan Fawr south of Moel Feity in the Black Mountains, the westernmost range of the Brecon Beacons National ...

extending the leisure boat facilities already being offered by the old South Dock. The barrage structure includes a boat

lock Lock(s) may refer to: Common meanings *Lock and key, a mechanical device used to secure items of importance *Lock (water navigation), a device for boats to transit between different levels of water, as in a canal Arts and entertainment * ''Lock ...

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure th ...

fish pass A fish ladder, also known as a fishway, fish pass, fish steps, or fish cannon is a structure on or around artificial and natural barriers (such as dams, locks and waterfalls) to facilitate diadromous fishes' natural migration as well as movemen ...

and

generator Generator may refer to: * Signal generator, electronic devices that generate repeating or non-repeating electronic signals * Electric generator, a device that converts mechanical energy to electrical energy. * Generator (circuit theory), an eleme ...

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...

. The turbine serves a dual use: acting as a power generator for the National Grid as well as being used to pump water back into the Tawe river system. The barrage scheme gave rise to a number of environmental concerns. Fish navigation up the river and

dissolved oxygen Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...

levels were problems that arose after completion. Salt water that came in at high spring tides sank to the bottom and stayed there, reducing oxygen levels. The Environmental Advice Centre was commissioned to undertake an

aeration Aeration (also called aerification or aeriation) is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration processes create additional surface area in ...

scheme trial in the River Tawe in the summer of 1998. The system was based on a diffuser design and propeller mixer, which proved highly effective at exporting the

saltwater Saline water (more commonly known as salt water) is water that contains a high concentration of dissolved salts (mainly sodium chloride). On the United States Geological Survey (USGS) salinity scale, saline water is saltier than brackish water, ...

from the deep area of the trial site and raising dissolved oxygen concentrations at the

bed A bed is an item of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many beds ...

. Following the success of the trial system a more extensive system was designed for the river for installation in 1999 -2000. The first stage of the installation of the designed system was undertaken in June 1999 and comprised a combination of diffusers and a large propeller mixer. The installation was conducted using a diving team to ensure optimal location of the diffusers within the river channel. The installation will be completed over two years to treat all the problem areas over a long reach of river and ameliorate the poor

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...

presented in these areas. Monitoring results from the system installed to date have indicated that aeration has effectively raised the oxygen concentration and assisted in the export of saline water from the system. Following the success of this work the Environmental Advice Centre is currently examining designs for other reaches of

tidal river A tidal river is a river whose flow and level are influenced by tides. A section of a larger river affected by the tides is a tidal reach, but it may sometimes be considered a tidal river if it has been given a separate name. Generally, tidal ri ...

within the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

that display similar problems. Following the success of the River Tawe aeration scheme the neighbouring

Welsh Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peop ...

city of

Cardiff Cardiff (; cy, Caerdydd ) is the capital and largest city of Wales. It forms a principal area, officially known as the City and County of Cardiff ( cy, Dinas a Sir Caerdydd, links=no), and the city is the eleventh-largest in the United Kingd ...

used the same method to improve the quality of the water in its newly created bay. Other fears that arose with the building of the barrage such as the raising of the

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

causing ground subsidence problems in the low-lying areas around the River Tawe. Since completion, no significant subsidence problems have arisen.

Notes

External links

The Tawe River and Swansea Harbour
{{Energy in Wales Dams completed in 1992 Energy infrastructure completed in 1992 Buildings and structures in Swansea Dams in Wales Tidal barrages Swansea Bay Hydroelectric power stations in Wales Pumped-storage hydroelectric power stations in the United Kingdom