WATER CATCHMENT AREAS 225 
Between 1500 and 1650 feet altitude ‘ : 84 acres, 
Mer eg cee PROG 307s Pees Legis. 
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na ToO7 ae OOO ie: Ac - su RLEG ees 
Total . 5360 acres, 
Practically the whole of the area is rough moorland 
grazing, with a few enclosed meadow and pasture lands, and 
27 acres of woodland. The Town Council have purchased 
outright nearly the whole of the watershed, and have planted 
about 100,000 larch at different periods during the last 
twenty years. This planting has been only partially success- 
ful, owing to the rabbit pest. The Town Council are con- 
templating a scheme of afforestation after the war, and are 
being advised by Prof. Pritchard on the matter. 
The Plymouth waterworks date from 1590, when Sir 
Francis Drake cut the open channel from Dartmoor to 
Plymouth, now known as the ‘leat, which conveyed the 
water supply for 300 years. From 1875 onwards the 
supply often ran short, owing to leakage from the leat, to 
the great increase of population, and to other causes. This 
led to the building of the Burrator reservoir and the con- 
veyance of the water by pipes in 1898. The growing in- 
adequacy of the water supply was not due, as has been 
stated, to the deforestation of Dartmoor in the last 300 
years. There is no evidence of the existence of woods in the 
Meavy drainage area in historic times. The watershed is 
very remarkable for its yield of water, which is greater than 
that of any other watershed in Britain. The whole of the 
catchment area, except 90 acres, is on granite, in which 
there are large fissures; and overlying the rock there are 
large tracts of peaty moorland. The rainfall is about 58 to 
60 inches annually. During wet weather the peat absorbs 
an immense quantity of water, which is stored up in various 
parts of the watershed in deposits of decomposed granite, 
that are in some places over 100 feet in thickness. This 
water is yielded pure and abundant in summer, when the 
flow of the stream is very much larger than on watersheds, 
where the geological formation is more or less impervious 
Q 
