HAMILTON'S WATER SUPPLY

Waikato Times, Volume 102, Issue 17285, 22 December 1927, Page 3

HAMILTON'S WATER SUPPLY

PRECAUTIONS DURING ARAPUNI TESTS. LAKE TO HOLD 5100 MILLION CUBIC FEET. FALL IN WAIKATO RIVER LEVEL. TOWN RESERVOIR CONTAINS HALF-DAY SUPPLY. In view of the threatened fall of several feet In the level of the Walkato River during the filling of the lake at the Arapuni dam, every effort Is being made by the Hamilton Borough Council to ensure that the power and water supply is not seriously affected. Complete precautions are being taken and excepting 1 for a slight restriction on the wasteful use of water In the borough, no difficulty Is likely to arise. , A failure of the water supply would be serious, as the town reservoir holds less than half a day's supply for consumption, but It Is considered there Is not the remotest possibility of this occurring.* From 11 o'clock on Christmas Eve the Arapuni lake will bo steadily Increased to the 320 feet mark, when It. will overflow down the spillway course. When Impounded water reaches that height there will be a lake containing 51 Op million cubic feet behind the dam. \

Owing to the lowering, of the river level, difficulty may arise in adequately supplying the reservoir, and residents of Hamilton are urged to avoid all wasteful usage, especially with garden hoses. This restriction is essential, for.lf the demand on the supply becomes too heavy, certain areas of the town might possibly have to 'be cut off.

"On Sunday, when the reduction In the water level first takes effect, a trial will be made at Hamilton.. Ordinarily the two borough pumps lift over'9oo,ooo gallons of water daily, but with one pump working full time it is possible to still take 750,000 gallons daily. From this it is appare.n that any temporary diminution in the supply will not be serious, the only restriction probable being the curtailment .of hosing of gardens between Christmas and New Year. The Arapuni staff and Hamilton Borough officials will be in close cooperation on the first day on which the reduction of the water level takes nlace, in order to note the effect, as it is impossible to foretell accurately what the exact drop will be at Hamilton ■ . '

Arrangements have been made to snal the man-holes and all cracks in the intake chamber, thereby causing a vacuum, which will have the effect nf, raising the level of the intake jft. Gin. above ordinary. If the river drops three feet below the present level it will be impossible to wort the two pumps. By the alteration in the level of the intaKe chamber and the creation of the vacuum, the' pumps can work successfully in the event of a 4ft. 6in. fall in •'the river level. . . ' The matter was discussed by the Hamilton Borough Council last night, when the Mayor stated that he thought the public would realise the and it would he necessary to .'prohibit the use of hoses for a period. Gr. Tidd said the- engineer was to be i commended for the businesslike,man- : ner in which he diad attended to the matter. The • engineer submitted a report

. outlining the precautions taken and stating- that at the. very worst 400.000 gallon's "of water- would be available for consumption dally. Restriction of Flow. The district electrical engineer was informed of the matter in a letter dispatched to him by the Hamilton Borough Council on December 13, when-it was stated it had been reported that during the operations the flow through the tunnel would be re- ' stricted to 250,6"00,000 c,ubic feet per day. This meant an average- of 2800 cusecs and as the flow would be varied to meet the demand at Hora Hora,, it was presumed that at times the flow would be less than 2800 cusecs. Concern was felt that, if such a drastic reduction in the flow took place, .the Hamilton water supply would cease to function. From information obtained as to ! the flow of water in the., river at Ara'puni, and from daily records taken at the pumping station, a graph had been drawn up connecting the river level at Hamilton with the cusecs at Arapuni, and from that graph it was believed • that when the flow at Arapuni was reduced to 2800 cusecs, the pumping units would cease to work. Consequently it was asked that the Department proceed with caution in the matter of restricting the flow and suggested that the minimum be fixed at 3000 cusecs until the actual effect of such reduction had been observed at the pumping station and reported on: • j When the gates were closed recently a drop in the river,level of two feet was noticed within twelve hours. The effect of a failure of the pumps to function was rendered more serious by i the fact that the total reservoir capa- - city was less than half one day's . supply. ,

the plant is overloaded and to cut off any power practicable. If that is not done, it is stated, then probably the whole supply will have to be cut off. Consumers are particularly requested to cut off all apparatus possible during milking hours from 4 a.m. to 8 a.m. and 3 p.m. to 6 p.m., owing to the increased load. The total volume of water required to fill the Arapuni lake to the 320 foot level, at which it will begin to overflow, is 5100 million cubic feet.

Figures taken when the statement was issued indicated that the lake was up to the 270 foot level, which meant ,that there was about 100 feet depth of water above the dam, but the amount of water then impounded was only about one-tenth of the total required. The total flow of the Waikato at present is about 730 million cubic feet per day, of which about 600 million cubic feet is required for Hora Hora, about 100 million cubic feet being impounded. Owing, however, to the difficulty of exact regulation, about 30 million is not being made use of, and runs to waste over the spillway at Hora Hora. The Only Alternative. The Waikato is liable to fall from now on, and if the season is a dry one, it may later have practically no surplus over Hora Hora requirements available for filling the lake, making action necessary now. The only alternative to making the most of the Christmas holiday period is to extend ■the time of filling indefinitely, with risk of interference with supply for an indefinite period. ' It is anticipated that with the present conditions the lake should be up to the 290 foot level at Christmas, at which level 2000 million cubic feet iof water will be impounded.. For the remaining 30 feet an additional 3100 million cubic feet of water will be required, and allowing a total daily flow in the river of 700 million cubic feet, with 250 million cubic feet allowed to flow to Hora Hora, the balance, 450 million cubic feet per day, should fill the lake in seven .days. The actual time will be more or less dependent on the rainfall and the actual rate of flow in the river at the time. Important consumers dependent on the electric power supply in Hamilton are the pumping station for the town's water supply, and a number of trading concerns. There is only one supply feeder, but the lead in past years has dropped considerably in the holiday week.