WATER CATCHMENT AREAS 225 



Between 1500 and 1650 feet altitude . . 84 acres. 



1250 ,, 1500 ,, „ . . 1550 ,, 



1000 „ 1250 „ ,, . . 2164 „ 



750 ,, 1000 „ „ . . 1562 „ 



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 v/hole 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 5 8 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 



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