50 facts for 50 years

Derwent at 50

On the 18 July 1967 HRH Princess of Alexandra officially opened the ‘new’ £5.5 million Derwent Reservoir.

To mark the reservoir’s birthday, Neil Buchanan the key engineer on the construction of Derwent, was presented with two framed letters from HRH Princess Alexandra and the reservoir’s visitors book that was signed by the princess and Mr Buchannan at the opening before he acted as her official guide.

The 3.5 mile long dam, can hold up to 11,000 million gallons which is equal to 625 bath fulls of water! It was the culmination of a huge feat of civil engineering and took six years to complete. 

Derwent Reservoir was formed by an earth dam across the River Derwent, a tributary of the River Tyne and forms the county boundary between Northumberland and County Durham.

Water from the reservoir flows through 2.2 miles of twin 41 inch diameter pipeline to the treatment works near the hamlet of Mosswood. The treatment works includes sedimentation tanks, filters and a laboratory.

The water then gravitates from the treatment works 27 miles to Washington to be distributed to customers in Durham, Sunderland and South Tyneside.


The reservoir collects the water running off 27,200 acres (110km²) of catchment. The average rainfall of the catchment is 37.5 inches (953mm). The reservoir provides a reliable daily yield of 30.5 million gallons (112,320 cubic meters per day). Compensation water is discharged to the river below the dam at an average rate of 5.75 million gallons a day, leaving a balance for each undertaking of 12.5 million gallons a day.

The Reservoir

The reservoir is one of the largest inland waters in England. It is 3.5 miles (5.6 km) long and covers an area of 1,000 acres (4 km²). The maximum depth of the water is 100 ft (30m) at the dam, and when full the reservoir will hold 11,000 million gallons (50,000,000m³).

Three farmsteads, two cottages and a charming old house, known as Millshield Mill we demolished before the reservoir was filled. Two miles of public road were submerged but were replaced by 4 miles of new road.

Construction of the reservoir, which cost £5.5 million, started in 1960 and water was first taken into supply in September 1966.

The Dam

The earth dam is 3,000 ft (914m) long and 119ft (36m) high above old river bed level. The volume of the dam is 2,600,000 cubic yards (2,000,000 m³). All the earth for making it was dug from the area, now under water, together with sand and gravel for most of the concrete. There are around 750,000 bricks in the dam wall.


Before dam could be built, the River Derwent had to be diverted through a tunnel 17ft in diameter and 646 yds long. When the dam was built, the tunnel was plugged which concrete 25ft thick. Upstream of the plug the tunnel is now full of water, while downstream it is dry and contains the pipes through which the water is taken from the reservoir.


1 Planning for Derwent Reservoir began in 1950
2 It cost £5.5 million to build
3 Work started on building Derwent Reservoir in 1960
4 It took six years to build
5 HRH Princess Alexandra, the Queens cousin, officially opened the reservoir on 18 July 1967
6 Three farms and two cottages were demolished to make way for the reservoir
7 Derwent Reservoir is the second largest reservoir in the north east
8 It holds 11,000 million gallons of water or 625 million bath fulls
9 Two miles of roads were submerged and replaced with nearly four miles of new road
10 At its deepest the reservoir is 30 meters deep
11 There are seven miles of shoreline
12 There are 750,000 bricks in the dam wall
13 The surface of water is four km²
14 The water from Derwent supplies customers in parts of Sunderland and Durham
15 Bankside fishing is available from March to November every year – any method available
16 Water from the reservoir flows through 2.2 miles of twin 41 inch diameter pipeline to the treatment works near the hamlet of Mosswood
17 100,000 people visit Derwent every year
18 More than 15,000 anglers visit Derwent every year
19 The reservoir collects the water running off 27,200 acres (110km²) of catchment
20 The reservoir is one of the largest inland waters in England
21 100 acres of trees were planted when the reservoir was built
22 The name Derwent comes from the Brythonic/Old Welsh word for oak ‘derw’
23 The reservoir compensates the River Derwent with 25 million litres of water every day
24 Derwent is one of Northumbrian Waters 22 reservoirs
25 Chris Packham from BBC’s Really Wild Show helped install an otter holt in 1999
26 There is a bird hide located on the north shore of the Derwent
27 Birds at Derwent include mallard, teal, coot, moorhen, tufted duck, pochard, goosander and greylag geese
28 Rare animals such as red squirrels and adders can be spotted around Derwent
29 The Derwent is located on the border between Northumberland and County Durham
30 Durham City Mayor, George Wharton hosted a charity fishing competition at Derwent with his entire entourage
31 On site shop stocks fishing tackle, gifts, snacks and drinks
32 Tour of the Reservoir the annual cycling road race is held around Derwent every year by Tyne Valley Cycling Club
33 In 2006 an osprey nesting platform was erected
34 There are three picnic sites each with toilets, car parking and walks
35 The River Derwent is a tributary of the River Tyne
36 Derwent is home to Derwent Reservoir Sailing Club
37 Fish up to 20lbs can be caught at Derwent
38 Neil Buchannan, retired NW civil engineer and the key designer of the dam, still visits our dams as a guest throughout the year
39 Derwent reservoir was designed and construction supervised completely by water company employees - all in house no out sourcing
40 4500 vertical drains sit below the dam to relieve pressure 24 hours a day /365 days of the year
41 The river Derwent was diverted in May 1962 through a tunnel to allow construction of the dam 42 Every year aspiring Reservoir Panel Engineers from the UK and overseas conduct there site training solely at Derwent Reservoir, this is the only UK site to host this prestigious event
43 The material for the dam construction was won within the reservoir area saving costs and impacts on the environment carbon footprint being kept to a minimum
44 260,000 cubic metres of clay was being placed in the dam per month at the peak of construction
45 A 15 min colour film was made during construction between 1961-1967 this is still shown to members of the public and engineers training to become reservoir panel engineers every year
46 Drones are being tested currently at Derwent reservoir to assess their suitability for inspection purposes for these large complex structures
47 What appears to be stonework used for the dam is in fact concrete, cleverly designed with roughened faces to match hand worked stone and the use of khaki cement colouring to match the surrounding natural stone
48 The earth dam is 3,000 ft (914m) long and 119ft (36m) high above the old river bed level
49 Tagged fish have been released this year which, if caught, could bag you £200!
50 Remember to drink eight glasses of Derwent’s finest tap water every day!

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walks around Kielder Water  

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