Our Water  

Did you know that only 2.5% of the world’s water is freshwater and that less than 1% is accessible and usable? 

Living in the south west of England, we are surrounded by water, be it coastal, in our rivers and canals or our reservoirs and lakes. Managed and supplied by South West Water, over 90% of our drinking water comes from surface water sources such as Roadford Lake, Colliford Lake and Wimbleball Lake.  

So, we know that our water comes from reservoirs, but which reservoir serves you, how big is it, and how much water does it actually hold? The oldest reservoir (dam) in the south west is Tottiford, which was constructed in 1861. Since then, 20 further dams have been built. Here’s a summary of our major water supply sources… 

Roadford Lake is situated between Launceston and Okehampton, and stores water from the River Wolf. It boasts a surface area of 295 hectares and a net storage of 34,500 megalitres – that’s equivalent to 145,822,972,901 cups of tea! The reservoir directly supplies North Devon via Northcombe Water Treatment Works near Okehampton and also makes releases to the River Tamar system. These releases are abstracted at Gunnislake and transferred to Crownhill Water Treatment Works in Plymouth, where the water is treated and goes on to supply Plymouth and parts of South West Devon. Roadford was completed in 1989. 

Wimbleball Lake, high on Exmoor, holds water from the River Haddeo, forming a reservoir with a net storage of 21,320 megalitres and a surface area of 150 hectares. Wimbleball supplies Exeter and parts of East Devon by releasing water into the River Exe. This water is subsequently abstracted at Tiverton and Exeter. Water is also supplied by pipeline to Wessex Water’s Maundown Water Treatment Works. This arrangement was put in place at the time of construction in the 1970s. Did you know? The water is 50m deep in places, and when the water is low, it is possible to see the ruins of a house built before the valley was flooded in the 1970s.  

Colliford Lake is situated on Bodmin Moor, and is Cornwall’s largest inland water, with a vast surface area of 366 hectares, or 900 acres. That’s the equivalent of about 682 football pitches! Colliford impounds water from the River St Neot, forming a reservoir with a net storage of 28,540 megalitres. The reservoir supplies parts of North and South East Cornwall directly, and makes releases to the River Fowey system, which are abstracted and treated at Restormel and distributed throughout much of the rest of Cornwall. 

Upper Tamar Lake in north Cornwall serves Bude and the surrounding area, including Bradworthy, Warbstow and Clovelly. The reservoir has a capacity of 1,477 megalitres and a surface area of approximately 32 hectares. Nearby Lower Tamar Lake was constructed in the 1820s and is steeped in history; the Bude Canal runs right up to the reservoir.  

Siblyback Lake is located on Bodmin Moor, which forms part of the Cornwall Area of Oustanding Natural Beauty (AONB). The impressive dam at Siblyback was completed in 1969 to supply east Cornwall, helping to meet the increasing demand on water supplies. It covers an area of 57 hectares and holds up to 3,185 megalitres of water. Did you know? One early proposal was to dam the main Fowey valley itself, upstream from Golitha Falls, which would have flooded a large part of the valley, including farms and livelihoods. Fortunately, this proposal was not approved; although the building of Siblyback Lake caused some minor destruction of farming properties, it did not reach the same scale as the Fowey valley scheme. 

Stithians Lake was opened in 1967, and is the largest inland water in west Cornwall. It can hold up to 5,205 megalitres and has a surface area of 109 hectares. 

Kennick, Trenchford and Tottiford form a network of three reservoirs which have a combined capacity of 2,011 megalitres when full. Constructed in 1861, Tottiford is the oldest reservoir on Dartmoor, followed by Kennick in 1881 and Trenchford in 1903.  

Wistlandpound is located in north Devon, on the edge of Exmoor National Park. The reservoir was completed in 1956; it can hold up to 1,550 megalitres and covers approximately 16 hectares, with water supplying Combe Martin, Ilfracombe and Barnstaple. Did you know? When water levels are low, you might be able to glimpse part of the Lynton and Barnstaple railway, which ran through the valley before it was flooded. 

Burrator is situated on the edge of Dartmoor, and supplies Plymouth, Tavistock, Princetown and South Devon. It has two dams (Burrator and Sheepstor) and was completed in 1898. The reservoir has a capacity of 4,210 megalitres and serves approximately 280,000 people. A particularly impressive sight is the cascading water from Devonport Leat, which finishes at Burrator as a waterfall.  

Fernworthy lies in the heart of Dartmoor, near Chagford. The reservoir gravity feeds into Trenchford Reservoir, and supplies Torquay with drinking water. It has a capacity of 1438 megalitres, and was constructed in 1942. There are several points of archaeological interest around Fernworthy; it is sometimes possible to see submerged clapper bridges when the water levels are low. 

At the time of writing, South West Water’s total reservoir storage was at 94.7%. Due to several successful water saving initiatives in the past, there has been no need for water restrictions since 1996. However we should and can all do our bit to use this precious resource wisely, which also benefits our wallets and the environment. Find out more here.

Useful notes  

1 megalitre equals 1 million litres  

1 hectare equals  2.47 acres   

Water is a precious resource and we can all do our bit to use it wisely, whatever the weather. Being Water Wise helps the environment and also helps keep household bills down.