254
( 12 )
92. This quantity is further supplemented by the yield of the catchment areas of these reservoirs and the yield of the springs intercepted by the Pokfoolum and Taitam conduits.
93. On reference to the rainfall statistics during the last 40 years as contained in the reports of the Director of the Government Observatory, it will be seen that the dry season not unusually commences as early as the month of September and extends to the end of the following April, or for a period of 242 days.
Dry seasons extending over periods exceeding the above have, however occured, for instance, those of 1859 and 1860, 1885 and 1886, 1886 and 1887, but these are most exceptional.
94. Dry Season of 1890-1891.-Shortly after the completion of the Taitam. Water Works, the exceptional dry season of 1890-1891 occurred, and on reference to my annual report for 1891 and the departmental records, I find that, from the 28th of August, 1890, when the water fell below overflow level in the Pokfoolum reservoir, to the 2nd of May, 1891, a period of 248 days, (after which heavy rains commenced) 99,815,800 gallons were drawn from the Pokfoolum reservoir catchment area, and 352,934,400 gallons were drawn from the Taitam reservoir catchment area,
95. The difference between the quantity stored in these reservoirs at the commencement and end of the above period was 62,500,000 gallons, and 305,000,000 gallons respectively.
96. We therefore get the quantity yielded, exclusive of that lost by evaporation from the surface of the reservoirs during this period, by the Pokfoolum catchment area 37,315,800 gallons and by the Taitam catchment area 47,934,400 gallons.
97. The rainfall amounted to 9.74 inches, so that the yield from these catchment areas during this period was 40 per cent. and 32 per cent. respectively of the actual amount of rain falling on them.
98. Tabulating the above figures, we get:--
1
Pokfoolum,
Taitam,
Valley.
Drawn from catchment area,
Loss in reservoirs.
Yield of catchment area.
Available per centage of rainfall.
gallons. 99,815,800.
gallons.
62,500,000
gallons. 37,315,800
40
352,934,400
305,000,000
47,934,400
32
99. Drought of 1895.-The year 1895 was the driest on record, the total rainfall being 45.84 inches, and, as during that year the water in the Taitam reservoir never reached overflow level, an opportunity is afforded of ascertaining the yield of its catchment area with a degree of accuracy not
hitherto obtained.
100. Tabulating the results obtained during that year, we get
Valley.
Loss in reservoir.
Pokfoolum,
Taitam,
Drawn from catchment area.
Yield of catchment area.
Percentage of rainfall.
gallons. 218,916,000
479,440,000
gallons. gallons. 12,199,000 206,717,000
72,083,000 407,357,000
48
56
The water intercepted by the conduits amounted to 165,274,000 gallons. 101. Considering the period from May to August, 1895, inclusive, during which the rainfall amounted to 35.60 inches, and tabulating the results, we get :---
Pokfoolum,
Taitam,
Valley.
Drawn from catchment area.
Gain in reservoir.
Yield of catchment area.
Percentage of rainfall.
gallons. 85,023,000
147,910,000
gallons. 48,781,000
168,466,000
gallons. 133,804,000
40
316,376,000
57
The water intercepted by the conduits during this period amounted to 74,260,000 gallons. 102. It must, however, be noted that, during the month of August, a considerable quantity of water, not included in the above, flowed over the overflow of the Pokfoolum reservoir.
It will therefore not be unreasonable to consider that the percentage of rainfall collected in the Taitam Valley might also have been collected in the Pokfoolum Valley, had there been storage capacity
available.
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