HUGE WATER SUPPLY.

Timaru Herald, Volume CXXIII, 26 March 1926, Page 10

HUGE WATER SUPPLY.

WORLD’S GREATEST DAMS COLOSSAL UNDERTAKINGS, The tragic bursting of a dam near Conway, m North Wales* reminds one of the tremendous importance ot tho engineering s.de of these constructions. In England the biggest dams have been constructed to .supply Manchester, Liverpool, and Birmiiignam with water. Manchester has already marie a huge lesorvoir of Thirlmere, .just under ‘‘the dark brow of the m.giity Helvellyn.” 'Jliero is a storage capacity, created by a huge dam at the Keswick end, of over 5,000,000,000 gallons. Lake Vyrnwy, in Montgomeryshire, had no existence until the Liverpool. Corporation dammed up,a small tributary of tho rivor Severn. Tho dam; is 1,172 ft long, 1611't high, and 127 ft thick at the bottom. Tlie storage capacity is 12,000,000,000_ _ gallons. The water leaves this artificial lake by a tunnel 2i miles long, driven through a hill. The tunnel, under the " Mersev, ■which carries the water into Liverpool, was tho first of its kind in the world. It is 900 ft long, and took four years to construct.

Birmingham also goes to Wales, to uilluer.ts of the Wye, for its water. It requires five, dams and live reservoirs, one of which, formed by the damming of the Klan Valley, is four miles long and has a capacity of 8,000,000,000 gallons. America is the land of great div.ns. The New Croton Dam impounds 32,000,000,000 gallons of water for the service ol New lork. Its ioumlation is a. level platform of masonry, to lay which half a million cubic yards of rock had to be removed. The inasonrv dam raised upon it is 20;"ft thick at the base, 250 ft high, and 1,2000 ft long. It required a million cubic yards of masonry, and supplies New York with 250,000,000 ga lions of water a day.

Another vast water supply for the same city has recently been constructed in the Katskill Mountains. It is__called the Ashokan .Reservoir, and is 127 miles from the city, the water taking three davs in making the journey. It supplies 500,000.000 gallons a day, and m case of nceessilv tills can be increased to 000.000,000. ' To make this enormous lake, seven villages were lamed and eleven miles of railway torn up. Its basin is 900 square miles in extent. Jt took 17,240 men seven years to make, and the total cost was over £85,000.000. ‘ The course of the river Ksopus is blocked by an enormous masonry dam over one-third of a. mile long, 200 ft wide, and 240 ft high. At eaeh end of the central masonry dam is an earthen one with a masonry core. 'These are eaeh 100 ft long and 800 ft thick at the base.

India has benefited greatly by the erection of irrigation dams, vast areas having been rendered fertile. The Tori Reservoir, one of the largest, was formed by damnvng up a valley by a. rampart a mile' and a-quarter long and 800 ft thick a.t the base. Rut the now dam across the river Vidavati, in Mysore. spans a gorge f ,200 ft wide. It is 107 ft, high and crosses a lake having a capacity of 82.848,000,000 eub'e leet of water. It is for irrigation purposes. The Assouan Dam on the Nile has added 2,500 square miles to the agricultural area of Kgvpt. It holds back 11,000,000,000 tons of water.