262
:( 20 )
This reservoir would have a capacity of 40,000,000 gallons with a top water level of 830 feet above Ordnance Datum, a catchment area of 60 acres which forms a portion of that of reservoir No. 1, and a maximum depth of 50 feet.
The waste weir is situated in the centre of the dam, that portion being constructed of masonry and cement concrete throughout, and has a length of 20 feet. It is anticipated that the depth of water over this weir will not exceed 3 feet.
The outlet arrangements will be similar to those described for reservoir on site No. 1. Estimated cost $56,000.
158. The run-off from the catchment area of this reservoir on the basis previously adopted during the months of May to August inclusive will not exceed 30,000,000 gallons, but the total run- off from the catchment area of the reservoir on site No. 1 will be 109,800,000 gallons. And the 39,000,000 over and above that required to fill the reservoir on site No. 1 can be diverted by a short length of catchwater constructed along the eastern slope of its catchment area.
No difficulty is therefore anticipated in practically filling these two reservoirs during the months of May to August inclusive from the catchment area available.
159. Proposed Reservoir on Site No. 3.-The proposed reservoir on site No. 3 situated immediatelyTM below the present waste weir of the Taitam reservoir would be formed by the construction of two masonry and concrete dams as shewn on Drawing No. 10.
This reservoir, which would practically form an extension of the existing Taitam reservoir, would have a capacity of 20,000,000 gallons with a top water level of 498 feet above Ordnance Datum, and a maximum depth of 27 feet.
The waste water would discharge over the top of the principal dam which has a length of 150 feet. It is anticipated that the depth of water over the weir will not exceed 4 feet.
The outlet commencing in a suitable valve well will be carried through the easterly dam and“ discharge into the existing Gauge basin at the entrance to the Taitam Tunnel.
The construction of this reservoir will involve a diversion of the road to Taitam Tuk, the building of a new residence for the caretaker and a new Police Station.
Estimated cost $60,000.
160. The completion of these works will practically exhaust the means available within the Taitam Valley for increasing the water supply unless recourse is had to pumping water from the lower levels.
TOTAL SUPPLY OBTAINABLE BY GRAVITATION FROM POKFOOLUM AND TAITAM.
161. The present storage capacity in the Pokfoolum Valley is 68,000,000 gallons, and on the completion of the proposed reservoirs in the Taitam Valley the storage capacity in that valley will be" 520,000,000 gallons making a total of 588,000,000 gallons.
162. The storage capacity required to secure 3,200,000 gallons per diem as shewn in paragraph No. 133 is 432,000,000 gallons; there would therefore be a surplus of 156,000,000 gallons which would be available for storing water in wet years for use during dry years.
163. After considering the rainfall tables contained in the appendices, I am of opinion that this additional storage may be relied upon to increase the daily supply available by at least 300,000 gallons bringing the total supply up to 3,500,000 gallons per diem, or equal to a supply of 15 gallons per head, per
diem to a population of 233,000 persons or the estimated population in 1,903.
164. Supplementing these works by the additions proposed in the Pokfoolum Valley, the supply from the several sources would be as follows
*
Catchment
Valley.
area.
Yield, May to August.
Yield, Sep- tember to April.
Total.
acres.
gallons.
gallons.
gallons.
Pokfoolum,
500
249,000,000
74,000,000
323,000,000
Pokfoolum Catchwater,
170
56,000,000
23,000,000
79,000,000
Taitam,
680
339,000,000
102,000,000
441,000,000
Taitam Catchwater, East,
220
72,000,000
30,000,000
102,000,000
"
"
West,
186
61,000,000
25,000,000
86,000,000
Streams Intercepted by Conduit,
74,000,000
96,000,000
170,000,000
Wongneichong Gap,
100
50,000,000
15,000,000
65,000,000
Catchwater,
90
30,000,000 12,000,000
42,000,000
931,000,000
377,000,000 1,308,000,000
365
Average supply per diem =1,106,000,000-3,583,000 gallons storage required 3,583,000 × 242 less the yield of the catchment areas during the months of September to April inclusive (867,086,000— 377,000,000) viz., 490,086,000 gallons. The storage capacity of the reservoirs will amount to 689,000,000 gallons leaving a balance of 199,000,000 gallons say, which may be relied upon to increase the daily supply to 4,000,000 gallons.
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