AFFORESTATION OF CATCHMENT AREAS 95 
considerable number of small farmers, and greatly reduced 
the number of sheep on the area, thus lessening the risk 
of contamination of the streams. The Corporation also 
adopted a scheme of afforestation in 1904, with the view 
of keeping the water pure. By 1908 about 408 acres 
had been planted with 1,640,000 trees. Smoke arising 
from the large manufacturing towns around Rivington caused 
some difficulty, as certain species failed to grow or ceased to 
thrive after a time. Beech and ash, however, were a success ; 
sycamore throve moderately ; and Corsican pine and Douglas 
fir did well in certain situations. Larch proved a failure. 
The growth of trees on the Rivington area has not been 
entirely successful, as some years ago a plague of voles 
did great damage. The smoke nuisance has gradually 
increased, and for the last four or five years forestry 
operations have been confined to filling up vacancies. The 
total area of the plantations, however, amounted on 30th 
June 1916 to 1300 acres, situated between 450 and 
1100 feet elevation. Beech, spruce, sycamore, ash, alder, 
Corsican pine, and oak were the main species planted, 
3,404,866 young trees being used. 
The Liverpool Corporation have not entered into any 
agreement with the Government in regard to the afforesta- 
tion of the Rivington area. The subject was discussed in 
1912, when a joint scheme for planting the Lancashire 
gathering grounds of the Liverpool and Bolton Corporations 
was proposed; but the matter dropped. 
Manchester owns two catchment areas, that of Lake 
Thirlmere in Cumberland, and the Longdendale Valley in 
Cheshire and Derbyshire. 
The natural catchment area of Lake Thirlmere is 7400 
acres, but water from a further area of 3600 acres was 
diverted into the lake, so that the total catchment area is 
11,000 acres, all owned by the Manchester Corporation. 
This ranges in elevation from 533 feet, the natural level of 
the lake, up to 3118 feet, the summit of Helvellyn. The 
geological formation is Lower Silurian, the rock being near 
