A collection of walks, discoveries, insights and pictures of exploring Dartmoor National Park
September 4, 2022
Water management across the centuries in the Upper Meavy and Hart Tor Brook Valleys
This post is split into three sections and considers water management in the Upper Meavy and Hart Tor Valleys for use by tinners and for the source of drinking water for the expanding population of Plymouth.
Firstly, the post covers the four leats in the area which were dug to provide water : a) for the tin works below Hart Tor (Tinners’ Reservoir and Leats 1 & 2); b) for Drinking Water for Plymouth Dock (Devonport Leat) and c) for Keaglesborough Tin mine located further down the Meavy Valley (Keaglesborough Leat).
Secondly, the intriguing dozen capped bore holes in the area, allude to a proposed 19th century reservoir that would have been constructed in the area. The post considers the impact of such a scheme and the antiquities that would have been lost.
Finally, the post looks at the water augmentation of Devonport Leat water from the Meavy and Hart Tor Brook by way of an iron pipe dating from 1915.
Part 1: Four leatsand Tinners’ Reservoir
The first part of this post is further subdivided into three parts, covering the water management associated with the Hart Tor Tinworks, Devonport Leat and Keaglesborough Mine.
a) Hart Tor Tinworks: In this area there are six different types of tinwork, namely: alluvial and eluvial streamworks, openworks, lode-back pits, shafts and shoad collection pits as described in Sandy Gerrard’s paper (Meavy Valley Archaeology, Site Report No. 10, HART TOR TINWORKS – 1998). It is theorised that the tinners would have required water during the “openworks” period of their prospecting and that the water they carried was used for sluicing away debris, although this is open to debate. It is possible that the two leats and a small reservoir which can still just about be discerned belonged exclusively to an earlier phase of streaming or prospecting than the “openworks” period.
b) Devonport Leat: A post about water management in this area wouldn’t be complete without mentioning Devonport Leat. Any visitor to the area could not fail to dramatic cascade of the leat over Raddick Hill and across the “Iron Bridge” (aqueduct). Devonport Leat was completed around 1802 to supply water to Plymouth Dock (known as Devonport after 1824).
c) Keaglesborough Mine: This complex comprises a large openwork, an adit, two dressing floors with sundry features, shafts, spoil heaps and two wheelpits. The mine is located near Raddick Plantation, Leather Tor Bridge and Raddick Lane about a mile to the south of the area covered in this post. The mining at Keaglesborough has references back to the 14th century with the latter day operations being in the 19th century. A tinners’ leat was dug in the early 19th century to convey water from the Meavy River to supply the mine at Keaglesborough (two waterwheels) and took water from the Meavy across to Hart Tor Brook where there was a feeder from which ran down the Meavy valley above a steep tinners’ cliff. The (dry) leat crosses Devonport Leat just above the aqueduct.
Part 2:Proposed reservoir from 19th Century.
The survey map (see previous hyper-link in sketch map caption) showing the capped boreholes can also be found on Dartefacts. Robert Naylor describes that: “These twelve items (capped bore holes) are relics of a C.19th project to create a reservoir in this valley”. He further shows the potential impact such a reservoir would have had by way of a annotated map showing the water level at the 360m contour line. It was this entry that partly inspired the author to write this post.
The twelve capped boreholes bare testament to an unsuccessful bid to consider the construction of a dam and reservoir in the Upper Meavy and Hart Tor Brook valleys. Ultimately, the geology of the proposed dam area proved to be the failure as the the granite wasn’t sound enough. The scheme was abandoned in favour of Burrator further down the Meavy Valley. This is mentioned in F.H Starkey publication, Exploring Dartmoor, on page 195 (and even shows a sketch of one of the capped boreholes!).
The land on which Burrator Reservoir is located was once (mainly) owned by two major landowners. One of the landowners was a Mr Bayly of Torr, Hartley, Plymouth (timber importer, his company became Bayly Bartlett). He wished to help the people of Plymouth and gave a large tract of land for the reservoir to be built However, the other landowner declined to sell at that time. The Hart Tor / Black Tor area was, at first, the preferred choice for a reservoir, but after the survey, Burrator seemed as a far better choice, with its adjacent stone quarries. The Burrator area was looked at again and the reluctant landowner eventually sold his tract of land to enable the reservoir to be built, which started in 1893 and was completed by 1898.
Had the Black Tor / Hart Tor reservoir scheme have gone ahead, the antiquities lost would have included 3 cairns, 2 stone rows and a Bronze Age settlement of 11 huts along as well as a lot of old tinners’ workings. The following pictures show the capped bore holes and the antiquities which were at risk.
Part 3: Water augmentationof Devonport Leat
The water in Devonport Leat comes from the West Dart, Cowsic and Blackabrook Rivers. Near to where the leat crosses the Meavy by an aqueduct the leat is supplemented with water via an iron pipe from Hart Tor Brook and River Meavy. Devonport Leat then eventually exits another iron pipe above Burrator Reservoir to supplement it. Thus most of the water from the Meavy, Hart Tor Brook and Devonport Leat sources eventually feed Burrator Reservoir, but not all. Some of is piped (or at least used to be) to a water treatment works at Dousland and before that it fed a hydroelectric turbine at Yelverton. The source of water feeding the Dousland treatment works depends on water quality – if the leat water is of poor quality then good quality water is pumped from Burrator reservoir to the works. Dousland treatment works supplies water down to Crownhill (Plymouth), Tavistock and Princetown. This is the normal arrangement, however, in times of drought or poor quality, South West Water can effect various water movements to maintain good drinking water. The take off to Dousland is just above the Devonport Leat outlet pipe waterfall.