|Primary inflows||River Haddeo|
|Primary outflows||River Haddeo|
|Basin countries||United Kingdom|
|Surface area||374 acres (1.51 km2)|
|Average depth||50 metres (160 ft)|
|Water volume||21,000 megalitres (17,000 acre·ft)|
The 161 feet (49 m) high dam is of concrete buttress construction and impounds the River Haddeo to provide a water storage capacity of some 21,000 megalitres over an area of 374 acres (1.51 km2). Aggregate for the dam came from a quarry at Bampton and sand from Uffculme. These were combined to give a pinkish tinge to blend in with the local geology.
At times of low flow in the River Exe, water is released into the river for abstraction downstream at Tiverton and Exeter. The effects of this regulation of the water flow from the lake have been studied by comparing the regulated River Haddeo and the neighbouring (unregulated) River Pulham. It showed that the main thermal effects of impoundment and regulation have been to raise mean water temperature, eliminate freezing conditions, depress summer maximum values, delay the annual cycle and reduce diurnal fluctuation.
In 2001 - 2002 South West Water commissioned a detailed assessment of fish population, physical habitat, flow and water quality data within the River Haddeo, since it has been subject to regulated releases from Wimbleball Reservoir, to identify potential bottlenecks restricting the development of juvenile salmon populations.
Managed by the charity South West Lakes Trust, the lake offers a popular location for walking, camping, birdwatching, angling, sailing, windsurfing, canoeing, rowing and kayaking. In December 2005 the trust was successful in obtaining funding for a £1 million project to provide a new rowing store, conversion of barn space into showers and changing areas, new sports equipment, an accessible bird hide, and interpretation, improved access, and signage around the site. In 2006 a new £1 million activity centre opened.
Wimbleball Sailing Club provides training, cruising and racing for its members, it is a non profit family sailing club operating every Sunday throughout the year and Wednesday, Friday and Saturday during the summer. The club is also home to a Sailability group providing sailing for the disabled.
The southern end of the lake is overlooked by the tower of Old Church of St James, Upton.
- "Incised Wooded Valleys" (PDF). Exmoor National Park. Retrieved 2007-11-24.
- Webb, BW; Walling, DE (1996). "Long-term variability in the thermal impact of river impoundment and regulation". Applied Geography. 16 (3): 211–223. doi:10.1016/0143-6228(96)00007-0. Retrieved 2007-11-24.
- "Habitat and Flow Improvements to benefit Atlantic Salmon in the River Haddeo". APEM Aquatic Scientists. Retrieved 2007-11-24.
- "Funding for Wimbleball Activities Centre". West Somerset Online. Retrieved 2007-11-24.
- "Wimbleball Lake". Somerset Rural Renaissance. Retrieved 14 May 2010.
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