5
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The supply has not, therefore, increased in proportion to the extension of the gathering-ground. The reason for this is that the waters of certain areas do not flow direct to the reservoirs, but are collected by catch-drains, which do not inter- cept the full quantity, during violent rain-storms.
A further reason is that. the total supply, given in the text, includes a large quantity of water picked up, along the course of the conduits, and which therefore is only affected indirectly, by the storage. The area of these intercepted gathering- grounds is not included in the areas, given in the statement, because the supply from them, is only partially developed.
works pro-
445
20. In addition to the works proposed by Mr. COOPER, for meeting the immediate Further wants of the City, works which have, as aforesaid, been fully carried out, he pro- posed by posed other deferred works, for meeting the future wants of the Colony. These Mr. COOPER.
are :—
(a.) The construction of three new reservoirs within, and fed from, the existing Taitam gathering-ground. These are shewn on Drawing No. 7, accompanying Mr. COOPER's Report of 1896. Sites Nos. 1 and 2, are on one of the tributary streams, above the existing reservoir and have a joint capacity of 110 millions of gallons, whilst that at site No. 3, is situated immediately below the by-wash of the same, and has a capacity of 20 millions of gallons.
·
(b.) The construction of a reservoir, below Taitain, at site No. 4, having a capacity of 100 millions of gallons, and a new gathering-ground of 375 acres of which 128 acres is intercepted by the Taitam catch- water. As the level of this reservoir is but 180 feet, above (). D., the water, stored in it, would have to be pumped into Taitam. (c) The construction of a small reservoir, in the bed of the Taitam stream, at a level of 108, having a capacity of 4 millions of gallons. This is to be merely a store-pond, to collect the dry-weather flow of the main Taitam stream, so that it may be pumped, with the water of Reservoir No. 4, into Taitam.
(d.) The construction of a large storage-reservoir, in the Pokfoolum valley, below the existing dam. The waters of this were to be con- ducted to the lower zone of the City, by a special pipe. The capacity of this reservoir was to be 78 millions, and special filter-beds were to be constructed, in connection therewith.
(e.) Raising the existing Pokfoolum dam, so as to increase its capacity by
23 millions of gallons.
None of these works are yet completed, and the small reservoir at No. 3 site. alone, is in hand.
Taitam Dis-
21. The following would be the probable effect of the proposed works. The reser- Effect of voirs, at sites Nos. 1, 2 and 3,* are, practically, within the existing gathering-ground deferred of Taitam reservoir. Their construction would not add to the total water-supply, due proposed, to the rain falling on, and flowing off from, the gathering-ground, but merely would trict. render a greater proportion thereof available for use, by storing water that would flow to waste. The effect of these works would be practically the same as that which would be produced by increasing the capacity of the Taitam Reservoir, by further raising the dam, were it safe so to do.
of augment-
22. When Mr. COOPER wrote his Report in 1896, he calculated, in accordance with As to the previous experience, that the reservoirs on sites Nos. 1, 2 and 3, as well as the advisability augmented Taitam dam would fill, even in a very dry season.† Subsequent events, ing storage however, have shewn that such is not the case.
* No. 3 indeed will receive the water from a small additional catchment area, which now escapes the Taitam Reservoirs.
On closer esamination of Mr. COOPER'S report, it does not appear clear whether he considered that all these reservoirs would fill in a very dry season.
without in- creasing the gathering- ground.