WATER CATCHMENT AREAS 245 
The total, 1435 acres, of which the Council owns only 
40 acres, situated on the Clydach area, consists of 1085 
acres of very hilly pasture and moorland, grazed by a few 
mountain sheep, and 350 acres of plantations. On this 
account the risk of contamination is considered negligible, 
and no special measures against it are taken. There are 
three storage reservoirs, Perthgelyn, Clydach Ynysybwl, and 
Darenlas; and only the water from the Darenlas reservoir 
is filtered. 
Rhondda Urban District Council obtains its water supply 
from : 
1. An intake on the upper course of the Rhondda 
River, at 1250 feet elevation, with a gathering ground of 
820 acres, rising to 1969 feet altitude (Craig-y-llyn). The 
weir formerly on the Rhondda River is no longer used. 
2. Llyn Fawr, a lake which has been converted into a 
reservoir of 200,000,000 gallons capacity, with a catchment 
area of 247 acres, situated between 1208 and 1969 feet 
elevation. j 
3. Nant Ystrad Ffernol, with a gathering ground of 257 
acres, between 1000 and 1690 feet elevation. 
4. Nant Selsig, Tyisaf Mountain, with a gathering 
ground of 358 acres, between 900 and 1600 feet 
elevation. 
The total area, 1662 acres, none of which is owned by 
the Council, is hill pasture and moorland, grazed only by 
sheep, and without houses or farmsteads, The water is 
filtered, and the gathering ground is periodically inspected. 
Besides Llyn Fawr, there is a small storage reservoir at 
Tynywaun near Treherbert. 
Aberdare Urban District Council obtains its water supply 
from three gathering grounds, totalling 1995 acres in 
extent : 
Nanthir and Nantmoel reservoirs, with a catchment 
area of 1075 acres, between 900 and 1250 feet elevation, 
about 4 miles north of Aberdare. 
Bwllfa reservoir, with a catchment area of 570 acres, 
