450
Additional gathering- ground as well as storage required.
Lower part
tuk valley to
12
It will be observed that, at the end of the water-year 1894-95, there was a balance of 1,363,642 gallons, to carry forward, at the end of April, to the next year, or rather more than a whole year's supply. But even this would not suffice, because there must, in addition, be space in the reservoir to receive the excess of rain over consumption, in the subsequent wet months. As it happened, the next year was one of low rainfall-54 inches. Therefore it will be more instructive to see what happened during the water-years 1893-94 and 1894-95. Here the balance brought forward on 1st May, 1894, was 1,092,022 gallons. From May to October, 1894, inclusive, 100 inches fell, as shewn in the statement given, and at the end of October there was a stock in hand of 1,872,928 gallons, or 780,906 gallons more than the stock at the commencement.
It is, therefore, evident that events may take place, which will necessitate carry- ing forward a balance of 1,368,642 at the end of the year and we might require room for 778,906 more, in all 2,147,548 storage capacity, or 675 days' supply would be the amount of storage required, to equalise the supply for a long cycle of years, and bring it up to the amount due to the average rainfall of the period in question.
In a recent paper, before the Institution of Civil Engineers, it was stated that in India two full years' supply was found to be necessary in the case of Town supplies. Applying these figures to Taitam the gathering-ground of which is 1,093 acres, then the daily supply, due to 85 inches of rain, is 3,456,000 gallons, and the storage to maintain it would be 3,456,000 × 675=2,332,800,000 gallons. These figures are not given as absolute but only to indicate the order of magni- tude of the storage requisite for full development of a given area.
Suffice it, therefore, for the present to say that the proposed reservoirs, within the existing Taitam gathering-ground, will add but little to the available supply.
30. Therefore, within the Taitam District, additional gathering-ground, with appropriate storage, is required, rather than an extra storage, with the same gathering-ground. Now additional gathering-ground can only be obtained by going lower down the valley, and pumping the water collected, up into the Taitam Reser- voir. The construction of reservoirs, at sites Nos. 4 and 5 should, in my opinion, take precedence of any works at sites Nos. 1, 2 and 3. Indeed, I am of opinion that it would be well to go further in this direction, and construct a reservoir or reservoirs still lower down, of ample capacity, so as to collect the rainfall of the whole gather- ing-ground, down nearly to sea level. Mr. COOPER does not give any particulars of his Nos. 4 and 5 reservoir-schemes, and I have difficulty in ascertaining the reasons why he limited himself to a small portion only, of the lower gathering-ground.
31. I recommend, therefore, that the Taitam-tuk valley, with its various ramifica- of Taitam- tions be surveyed from about high-water mark, up to about 250 feet O. D. be carefully be surveyed surveyed, with a view of ascertaining what storage accommodation can be obtained, by the construction of one or more reservoirs, so as ultimately to develop, to the utmost possible extent, the full gathering-ground Gauges should also be erected, to measure the flow of the main Taitam stream, as low down as possible.
for reservoir
sites.
Advantages of a low-
level supply
32. One of the advantages of the low-level pumping scheme is that considerable relief could be obtained, almost immediately. A gauge has been erected, at or near by pumping. the site No. 5. This gauge has been recorded for some time past. Taking last season's record, it appears that at least 30 millions of gallons passed this gauge, during September last, and about half that amount in October. I am convinced, by personal inspection, that this gauge is not measuring the full flow of the stream, and, moreover, it is not sufficiently large to measure, even an ordinary flood-discharge, so that the recorded flow is considerably below the truth. If, therefore, a small re- servoir had been in existence, at site No. 5, and a steam-engine and pipe had been provided, about 45 millions of gallons could have been pumped into the Taitam tunnel, or about the stock in hand at the moment of writing this Report.