seen from high up on Harter Fell
|Location||Lake District, Cumbria|
|Type||reservoir, natural lake|
|Primary inflows||Mardale Beck, Riggindale Beck|
|Primary outflows||Haweswater Beck|
|Max. length||6.7 km (4.2 mi)|
|Max. width||900 m (3,000 ft)|
|Surface area||3.9 km2 (1.5 sq mi)|
|Average depth||23.4 m (77 ft)|
|Max. depth||57 m (187 ft)|
|Water volume||76,600,000 m3 (62,100 acre·ft)|
|Residence time||500 days|
|Surface elevation||246 m|
Haweswater is a reservoir in the English Lake District, built in the valley of Mardale in the county of Cumbria. The controversial construction of the Haweswater dam started in 1929, after Parliament passed an Act giving the Manchester Corporation permission to build the reservoir to supply water for Manchester. At the time, there was public outcry about the decision, as the valley of Mardale was populated by the farming villages of Measand and Mardale Green and the construction of the reservoir would mean that these villages would be flooded and lost and the population would have to be moved. In addition, the valley was considered one of the most picturesque in Westmorland and many people thought it should be left alone.
Originally, Haweswater was a natural lake about four kilometres long, almost divided in two by a tongue of land at Measand; the two reaches of the lake were known as High Water and Low Water. The building of the dam raised the water level by 29 metres (95 feet) and created a reservoir six kilometres (four miles) long and around 600 metres (almost half a mile) wide. The dam wall measures 470 metres long and 27.5 metres high; at the time of construction it was considered to be cutting-edge technology as it was the first hollow buttress dam in the world, being constructed using 44 separate buttressed units joined by flexible joints. There is a parapet, 1.4 metres (56 inches) wide, running the length of the dam and from this, tunnelled supplies can be seen entering the reservoir from the adjoining valleys of Heltondale and Swindale. When the reservoir is full, it holds 84 billion litres (18.6 billion gallons) of water. The reservoir is now owned by United Utilities plc and plays a vital role in supplying about 25% of the North West's water supply.
Before the valley was flooded in 1935, all the farms and dwellings of the villages of Mardale Green and Measand were demolished, as well as the centuries-old Dun Bull Inn at Mardale Green. The village church was dismantled and the stone used in constructing the dam; all the bodies in the churchyard were exhumed and re-buried at Shap. Today, when the water in the reservoir is low, the remains of the submerged village of Mardale Green can still be seen as stone walls and the village bridge become visible as the water level drops.
Manchester Corporation built a new road along the eastern side of the lake to replace the flooded highway lower in the valley, and the Haweswater Hotel was constructed midway down the length of the reservoir as a replacement for the Dun Bull. The road continues to the western end of Haweswater, where a small car park has been built; this is a popular starting point for walkers who want to climb the surrounding fells of Harter Fell, Branstree and High Street.
Lake District writer and fell walker Alfred Wainwright had this to say on the construction of the Haweswater dam in his A Pictorial Guide to the Lakeland Fells:
- "If we can accept as absolutely necessary the conversion of Haweswater [to a reservoir], then it must be conceded that Manchester have done the job as unobtrusively as possible. Mardale is still a noble valley. But man works with such clumsy hands! Gone for ever are the quiet wooded bays and shingly shores that nature had fashioned so sweetly in the Haweswater of old; how aggressively ugly is the tidemark of the new Haweswater!"
There is a population of schelly fish in the lake. They are believed to have lived there since the last Ice Age.
Haweswater is the only place in England where a golden eagle was resident. A pair of eagles first nested in the valley in 1969 and the male and female of the pairing changed several times over the years, during which sixteen chicks were produced. The female bird disappeared in April 2004, leaving the male on its own.
There is an RSPB observation post in the valley of Riggindale, where the pair had their eyrie (the viewpoint is manned by volunteers on weekends and bank holidays from Easter to the end of August). It is possible a replacement female will be drawn to the area. However, the last sighting of the lone male was in November 2015, and it is believed that the 20-year old bird may have died of natural causes. 
In 2012 the RSPB was leased Naddle Farm, not far from the dam, by the landowner United Utilities. The aim is to combine the improvement of wildlife habitats and water quality with running a viable sheep farm. Moorland and woodland habitats are being improved for birds as well as the rare small mountain ringlet butterfly. Measures include grip blocking, heather replanting, juniper woodland planting (especially in the ghylls).
"Possibly 'Hafr's lake', from a pers.[onal] n.[ame] such as ON [Old Norse] 'Hafr' or a postulated OE [Old English] 'Hæfer', and 'water'..."" 'wæter OE, water ModE' the dominant term for 'lake'..."
Haweswater (2002) is also the name of a novel by Sarah Hall, set in Mardale at the time of the building of the dam and flooding of the valley. It won the Commonwealth Writers' Prize for a First Book in 2003. The novel was released in the United States as a paperback original in October 2006, by Harper Perennial.
Haweswater is the lake that can be seen from the door of 'Crow Crag' in the film Withnail & I although filming of the cottage itself was done elsewhere.
- McNamara, Jane, Table of lake facts, Environment Agency of England and Wales, archived from the original on June 28, 2009, retrieved 2007-11-13
- Wainwright, A (2005). A pictorial guide to the Lakeland fells. Book 2: The far Eastern fells (2nd ed.:revised by Chris Jesty ed.). London: Frances Lincoln. pp. n.p. "Some personal notes in conclusion". ISBN 9780711224667.
- "Haweswater". RSPB website. Retrieved 4 March 2007.
- "England's last Golden Eagle feared dead". Retrieved 26 May 2016.
- "Haweswater". RSPB website. Retrieved 20 August 2012.
- Whaley, Diana (2006). A dictionary of Lake District place-names. Nottingham: English Place-Name Society. pp. lx,423 p.157. ISBN 0904889726.
- Whaley, 2006, p.422