4.— THE NEW WATERWORKS FOR PORT ELIZABETH, 

 SOUTH AFRICA. 



[Abstract.] 



By W. IxGHAM, M.I.C.E., M.I.M.E., Chief Engineer. 



The old Avaterwoi'ks at Petit Elizahetli comprises a storage reser- 

 Aoir wit!i a capacity of 30 million gallons situated some 2-t miles from 

 Port Elizabeth, and known as the Van Staaden's Reservoir, a series 

 of sanfl filter beds, a pumping station and intake on the Van Staaden's 

 River about 3 miles below the dam, a pipe line 24 miles long and a 

 covered service reservoir with a capacity of 1| million gallons. The 

 above scheme was sufficient to supply between 400,000 and 500,000 

 gallons per da\' ; but this was found to be insufficient, and only gave 

 from 10 to 12;y gallons per head of population. The population, whicli 

 is 40,000, is composed of 21,000 Europeans, and 19,000 natives, 

 Malays, Indians, and Chinese, and the quantity of water used per 

 head by Europeans is over twice as much as that used by the coloured 

 races. The new scheme will give an additional 11 million gallons per 

 day, making a total supply of about 2 million gallons, or sufficient 

 water for 90,000 people, allowing 30 gallons per head to the whiti^ 

 and 15 gallons per head to the coloured population, if equall}' divided. 

 The new catcliment area is 31-63 square miles in extent, and is 

 situated in the Eland's Ri\er Valley. The geological formation is 

 quartzite (Table Mountain series), and the area is covered for the 

 most part with lonij ojrass. The height of the catchment area is be- 

 tween 960 ft. and 3000 ft. above sea-level. The water is soft, but the 

 clilorine is rather high ; this is, however, due to the proximity of 

 the catchment area to the sea, and decreases as the distance from 

 the sea-board increases. The average rainfall for the whole area 

 is between 33 and 34 ins. per annum, and the evaporation from a 

 free water surface is 45 to 50 ins. per annum. The annual lun-off 

 varies from 10 per cent, to 40 per cent, of the rainfall ; the higher 

 ratio being due to large floods which usually come down in Septem- 

 ber or October and occasionally in March. The Sand and Palmiet 

 ri^■ers have a higher dry weather How, but a smaller fiood discharge, 

 per unit of area than the Bulk lli\er, the former having a minimum 

 dry weather flow of 0-43 cubic ft. per second per 1000 acres, and 

 the latter 0'12 cubic ft. The new scheme comprises two storage reser- 

 voirs ; two filter plants on the Candy system ; a pipe line 40 miles in 

 length, with a large number of bridges and a tunnel a little o\-er a 

 (piarter of a mile in length; a covered service reservoii- in St. George's 

 Park, with a capacitv of 2 million gallons; a telephone line 43 miles 

 in length, and two caretakers" houses. The Sand River Reservoir, 

 which has a capacity of 187 million i;allons, is constructed a little 

 below the junction of the Sand and Palmiet rivers, about 38 miles 



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