SOME MIGHTY DAMS

Hawera Star, Volume XLV, 27 March 1926, Page 11

SOME MIGHTY DAMS

QUENCHING THE WORLD’S THIRST

rpilE .tragic bursting of a dam near Conway, in North Wales, last year, Reminded people of the tremendous importance of the engineering side of these constructions. In England tire biggest dams have been constructed to supply Manchester, Liverpool and Birmingham with water. Manchester has already made a huge reservoir of Tliirlmere, just under “the dark brow-of mighty Helvellyn. ’’ There is a storage capacity, created by a huge dam, of over 8,000,000,000 gallons. Hake Vyrnwy, iu Montgomeryshire, had no existence until the Liverpool Corporation dammed up a small tributary of the River Severn. The dam is 1172 feet long, 1(31 feiet high, and 127 feet thick at the bottom. The storage capacity is 12,000,000,000 gallons. The water leaves this artificial lake by a tunnel two and a-quartor miles long, driven through a hill. .The tunnel under the Mersey which carries the water into Liverpool was the first of its kind in the world. It is 000 feet long, and took four vears to construct.

Birmingham also goes to Wales, to affluents of the Wye, for its water. It requires five dams and five reservoirs, one of which, formed by the damming of the Elan Valiev, is four miles long and has a capacity of 8,000,000,000 gallons. America is the land of great dams. The’ New Croton Dam impounds 32,000,000,000 gallons of water for the service of New York. Its foundation is a level platform of masonry, to lay which half a million cubic yards of l-ock had to be removed. The masonry dam raised upon it is 205 feet thick at the base, 250 feet high, and 1200 feet long. It required a million cubic yards of masonry,.and supplies New York with 250,000,000 gallons of water a day. Another vast water supply for the same city has recently been construct ed in the Catskill Mountains. It is called the Ashokan Reservoir-,- -and.;,, is 127 miles from the city, the water taking three days in making the journey. It, supplies 500,000,000 gallons a day, and in case of necessity this can be increased to 900,000,000.

To make this enormous lake, seven villages -were razed and 11 miles, of railway torn up. Its basin is 900 square miles in extent. It took .17,240 men seven years to make, and the total cost was over £35,000,000. The ’ course of the rivjer Esopus. is blocked by an enormous masonry dam over one-third of a mile long, 200 feet wide, and 240 feet high. . At each end of the central masonry dam is an earthien one with a masonry core. These are each lOOOfeet long and 800 feet thick at the base.

India has benefited greatly bv the erection of irrigation dams, vnst.niteas having bean re/ndered The Tori Reservoir, one of the largest, was formed by damming up a valley by a rampart a mile and a-quartter long and 300 feet thick at the base. But the new dam across the River Vedavati, in Mysore, spans a gorge 1200 feet wide. It is .1(37 feet high and creates a lake having a capacity of 32,348,000,00 cubic feet of wat/er. It is for irrigation purposes. The Assouan Dam. on the Nile has added 2500 square miles to the agricultural area of Egypt, . and regulates the annual overflow of Nile water. In making it, it was first necessary to blast an immense dyke in the granite across the bed of the river. Upon this was erected a huge wall, pierced by one hundred sluices, .and holding up a lake as long as the distance between London and Nottingham. It holds back 1,000,000,000 tons of water!