A POPULAR place in the Yorkshire Dales to go for a short walk, maybe when lockdown eases, is Grimwith Reservoir, between Hebden and Greenhow, in the heart of the Yorkshire Dales National Park.

Here Colin Speakman reviews a book on the fascinating history of this expanse of water.

A new book, Development of Grimwith Reservoir, by retired Skipton Civil Engineer Jim Crossley tells the complex story of the building and opening of not only the present reservoir, but the earlier, much smaller reservoir built in the higher valley of the River Dibb, opened in 1864.

But what makes Jim’s account especially valuable is that Jim is more than just a historian of the building of the second reservoir, opened in 1983, but part of that story - both as an eyewitness and participant in what was one of greatest pieces of civil engineering in the Dales in the 20th century.

The reasons for the building of both reservoirs was the need for water supply for the expanding city of Bradford – again reinforcing the close cultural and economic links between Bradford and the Yorkshire Dales. But the first reservoir as Jim explains did not directly provide drinking water as such, but was initially built as a compensatory reservoir to provide water to power the great textile mills downriver, in Addingham, Burley and Otley to ensure sufficient water at times of drought, to ensure adequate river levels when water from the huge gathering grounds of Barden Moor was being extracted into the two Barden Reservoirs for use in Bradford. The water from Barden was fed directly into the great underground aqueduct system leading to Chelker storage reservoir, and onwards to Chellow Heights Water Treatment Plant in Bradford.

Plans in the 1890s to enlarge the first Grimwith Reservoir to provide drinking water were abandoned in favour of the Upper Nidderdale Reservoir scheme, with the huge reservoirs at Angram and Scar House being constructed over the next 30 years.

But by the 1970s even these were insufficient to meet demand. The decision was taken to totally rebuild Grimwith Reservoir to create a massive new storage capacity of 4,889 million gallons or 21,770 thousand cubic litres, almost 8 times the capacity of the original reservoir. But transferring the water to Bradford uses a perhaps surprising natural aqueduct – the River Wharfe itself. The outflow of the reservoir feeds into the little River Dibb joining the Wharfe below Burnsall, but this water is extracted at Lob Wood Pumping Station alongside the river and pumped to Chelker Reservoir to join the Nidd Aqueduct to Bradford.

The prime focus of this fascinating book is the building of this second Grimwith Reservoir, stage by stage, in the late 1970s and early 1980s, the huge excavation and building works, coping with complex local geology, old bell pits, quarries, lead mine workings, extreme weather and even collapsing tunnels. Local stone was used throughout for embankment walls, the Control House, Pumping Station, weirs and other buildings. An intriguing task was the rescue of High Laithe, a 16th century monastic barn.

Other buildings were carefully removed and conserved, native trees planted, and a small nature reserve created in Blea Gill in the western corner, now noted for wigeon and ringed plover.

A sailing club was allowed to use the reservoir waters, with a ban on power boats to avoid noise and disturbance, both to wildlife and to other users of the area. There is a small visitor car park, toilets, picnic tables, but no other facilities.

What has proved to be of inestimable value is the level walkway of some four miles created around the reservoir to permit quiet recreation and nature observation.

Development of Grimwth Reservoir by Jim Crossley is published by the author, price £10 with postage and packing (including £2 donation from every copy sold to Water Aid). To order send your name and address by email to ann.shadrake@friendsofthedales.org.uk. indicating “Grimwith book request”.