The River Dee (Welsh: Afon Dyfrdwy) is a 70 mile (110 km) long river, which rises in Snowdonia, Wales, flows north via Chester, and discharges to the sea into an estuary between Wales and the Wirral in England.
The total catchment area of the River Dee up to Chester Weir is approximately 1800 km². The average rainfall over the catchment is estimated to be 640 mm yielding an average flow of 37 m³/s. The larger reservoirs in the catchment are:
* Bala Lake (Llyn Tegid) - 400 acres (1.6 km²)
* Llyn Brenig - 370 acres (1.5 km²)
* Llyn Celyn - 325 acres (1.3 km²)
The River Dee has its source on the slopes of Dduallt above Llanuwchllyn in the mountains of Snowdonia in Merioneth, Gwynedd, Wales, and then passes through Bala Lake. The path of the river trends generally east-south-east as it descends off the Ordovician Denbigh moors, over the man-made Horseshoe Falls and through Llangollen, generally skirting the outcropping Karstic limestone exposures north of Llangollen. East of Llangollen, Thomas Telford's Pontcysyllte Aqueduct , of 1805, carries the Shropshire Union Canal 120 feet (37 m) overhead.
One of the major tributaries of the Dee, the Afon Alyn crosses the carboniferous limestone from Halkyn Mountain and down through the Loggerheads area before making its confluence near Mold. Throughout the length of the Alyn there are numerous sinkholes and caverns and during the summer months long stretches of the river bed run dry. These caves include Ogof Hesp Alyn and Ogof Hen Ffynhonau. A significant part of this lost flow re-emerges in a man-made tunnel entering the west bank of the Dee estuary carrying some 12 million imperial gallons per day (600 L/s). This tunnel was originally constructed to drain metal mines in Halkyn Mountain. Once the main river Dee approaches the Cheshire border and the carboniferous coal measures, it turns sharply northwards before meandering up to Chester. This long stretch of the river drops in height by only a few feet and can be regarded as a highly linear lake. The rich adjoining farmland has many remnants of abandoned coal workings and deep clay-pits used to make bricks and tiles. A number of these pits are now being used as landfill sites for domestic and commercial waste.
At Holt and Farndon, the river crosses into England under a medieval bridge and then passes under the A55 and onward to Chester. At Chester the river passes and around the Earl's Eye(s) meadow, a protected green space between the Boughton and Handbridge suburbs of the city. The river is crossed by a ferry from Boughton to the meadows, and at the Groves, a Victorian riverside recreation area with a bandstand, benches and boat cruises, by two bridges. The first is the Queen's Park Suspension Bridge, which forms the only exclusively pedestrian footway across the river in Chester. The second is the Old Dee Bridge, a road bridge and by far the oldest bridge in Chester, being built in about 1387 on the site of a series of wooden predecessors which dated originally from the Roman period.
Above the Old Dee Bridge, the river has a weir, which was built by Hugh Lupus to supply power to his corn mills. Throughout the centuries the weir has been used to power corn, fulling, needle, snuff and flint mills. The same weir was used as part of a hydro-elecrtic scheme in 1911 with the help of a small generator building which is still visible today, used as a pumping station for water since 1951. However the first water pumping station here was set up in 1600 by John Tyrer who pumped water to a square tower built on the city's Bridgegate. It was destroyed in the Civil War but an octagonal tower built in 1690 for the same purpose lasted until the gate was replaced with an arch in the mid-18th century.
On this weir is a fish pass and fish counting station to monitor the numbers of salmon ascending the river. A little further downstream stands the Grosvenor Bridge (designed by architect Thomas Harrison of Chester), which was opened in 1833 to ease congestion on the Old Dee Bridge. This bridge was opened by Princess Victoria five years before she became Queen. The other side of the Grosvenor Bridge is the Roodee, Chester's race course and the oldest course in the country. This used to be the site of Chester's Roman harbour until, aided by the building of the weir, the River Dee silted up to become the size it is today. The only curiously remaining reminder of this site's maritime past is a stone cross which stands in the middle of the Roodee which exhibits the marks of water ripples. To the end of the Roodee the river is crossed again by a second bridge, now carrying the Chester–Holyhead railway line, before leaving Chester. It was the scene of one of the first serious railway accidents in the country, the Dee bridge disaster.
To the north of Chester, the river flows along an artificial channel, excavated when Sealand and Shotton were reclaimed from the estuary.
This 'canalised' section runs in a straight line for five miles (8 km) and passes beneath three road bridges at Queensferry and Shotton. The first is a fairly modern fixed arch bridge, the second, the Queen Victoria Jubilee Bridge, is of the rolling bascule type and the third is a modern fixed cable-stayed bridge connecting north Wales with England which opened in 1999.
Between the second and third road bridges is the Hawarden railway bridge, originally constructed as a swing bridge but now never opened. It carries the Birkenhead–WrexhamBorderlands Line line over the river.
The river then opens out into the Dee Estuary, forming the north eastern tip of the North Wales coast and the western coast of the Wirral. Towns along the coast include Flint and Holywell on the Welsh side and Neston, Parkgate, West Kirby and Hoylake on the Wirral side.
Large parts of the catchment are devoted to agriculture and there a number of abstractions made from the river for summer irrigation. The volumes involved are not however significant.
From Chirk downstream, the river valley has supported a wide range of industries that were initially drawn to the area by the presence of coal mines and later by the deep deposits of carboniferous clays used to make bricks and tiles.
The coal industry in particular gave rise to a number of chemical industries some of which survive to this day and which both take water from the river and discharge their cleaned up effluent back into the river. Industries in the valley include commercial chemicals manufacturer, wood chip and MDF fabrication, cocoa milling, fibreglass manufacture, waste disposal (in old clay pits) and a great variety of smaller industries concentrated around Wrexham. The main impact on the river of these industries is their thirst for a dependable good quality water supply.
There are a number of direct water abstractions upstream of Chester by three water companies and by the canal. The size of the abstraction is very large compared to the summer flow and the flow in the river is very highly regulated through the use of reservoirs to store water in the winter and release it in the summer. The whole system is managed as the River Dee regulation system. Below Chester water is also abstracted as cooling water by the gas-fired power station at Connah's Quay. Process and cooling water is also abstracted for the paper mill and power station at Shotton.
The Dee used to be a popular whitewater kayaking and touring river (particular the grade III/IV whitewater section upstream of Llangollen). It stays high after rain for longer than most British rivers and is paddleable year-round (thanks to the River Dee Regulation System). Canoeing used to be allowed on about twelve weekends per year, and tens of thousands of canoeists descended on Llangollen for recreational paddling (several Dee tours were held every winter), slalom competitions, and wild water races.
Public access to the river is arranged by the Welsh Canoe Association. In 2003, negotiations with the angling associations owning fishing rights on the Dee broke down. The anglers wanted to restrict the numbers of paddlers on the river when paddling was allowed but the Welsh Canoe Association wanted to renew the previous agreement. As a result, all canoeing on the river was banned. In November 2004, a protest about the lack of access on the Dee, and to rivers across England and Wales, was held in Llangollen. More protests are likely in the future. Following the failure of the access agreement, many canoeists use the river at will from the numerous access points along its banks.
Canoeing is permitted on one 100 m long rapid 1 km upstream of Llangollen, and on some flat sections far downstream in England.
The river has been famed as a mixed fishery with Salmon and trout fishing, mostly in the upper waters and a good coarse fishery in the lower reaches. A major pollution in the middle reaches in the late 1990s did extensive damage to the fishery from which it is now largely recovered.