rainfall during the month.
10
With these data it is possible to calculate the proportion of the gross rainfall which is available for distribution.
43. The following table gives the stock in hand, and the discharge from the reservoir during the month, in millions of gallons as well as the rainfall in inches.
The nett water collected during the month is thus calculated
Stock in reservoir 1st January, 1889 Discharge from reservoir during January
Millions of gallons.
305:50
40.50
Remainder
265·00
27140
Therefore reservoir received from the gathering
ground.
6.40
Actual stock on 1st February
Rainfall in January, 073 inch
6:40
Therefore millions stored per inch of rain
8.77
173
One inch of rain on 700 acres
15-84
Percentage available
8·7 x 100
15.84
Per cent.
55
44. When the figures are thus manipulated, numerous anomalies appear. Sometimes vastly more than the rainfall is collected, at other times a very small proportion. These anomalies may be explained by the fact that the streams go on running, long after rain has ceased, being fed by water which has percolated into the soil and which reappears as springs.
These anomalies can, to some extent, be eliminated by averaging the various results or by taking the total, omitting those cases in which an overflow appears to have taken place.
45. The result is, that during four years 173-67 inches of rain gave a nett volume of 1,147-84 million gallons collected, or at the rate of 663 millions per inch or 42 per cent. nett, 58 per cent. being lost by evaporation and percolation. As only those months could be used during which no overflow took place, this ratio can only be applied to the dry season. In the wet season the percentage of flow is greater, and may be taken at 70 per cent., according to data obtained at Pokfulum.
it
that the
46. From a record extending over a period of 39 years appears lowest rainfall during any season from 1st May to 30th April inclusive, occurred in 1858-59.
The rain 1st May to 30th September ...
1st October to 30th April
N
45.5 inches.
5.9
""
Total
51.4 inches.
1890.
1889,
11
COMPARISON OF RAINFALL WITH WATER COLLECTED IN TYTAM RESERVOIR.
Nett
Stock in Reservoir on first
of month.
Discharge from Reservoir during
Month.
month.
Nett Quantity collected in Reservoir during month.
Loss by evaporation and porcolation! during 70onth.
Water collected per inch of mintull.
Total Water
Total
Rainfall
collected
Rainfull
during
during
during
group of
morth.
group of
obantvm-
chserva- tions.
tione.
Millions of Gallons.
Juches.
(January
305-50
40.50
6-40
8-77
0.73
February March
271.40 40-20
7-90
10-98
0-72
239.10 69-80 16.20
6-50
2-49
April...
195-50 45.90 80-60
0.56
111-10
12-27
16-21
May
230-20 43-00
48-81
June
300-30 I180
9-72
Conduit
broken.
July
311-40 35.50
4-57
August
312-00 46.90
18.14
September
312.00 45.50
11:80
October
311·10 46.70
8.72
November
311-70 55.90
1.54
December
304.20 45-50 15-00
88-23
15.00
0.17
0-17
(January
273-70 47-40 10-00
4-17
2:40
February
242-30 37.50
3:30
2-24
1-17
March
208-10 43.50
12.90
3:07
4.20
April...
177.50 46.50
10-30
5.25
1.96
May
141-30 56.50 86.90
7-73
11-24
June...
July
August September October
171-60 48.60 51.30 274-30 55·10 91-30 310:50 58-10 306-80 55.70
3:45
14.83
4.04
266.00 22-60 58.70
8.95
1-94
282-00 50.30
4:00
200-00
0.02
November
235-70 50-30
1.74
170-00
5.74
0:01
December
187-10 51-80
5:30
Nil.
1.37
1:40
(January
130-00 50.00
4-80
Nil
0.04
February
7720 37-30
2-00
Nil
0-24
March
37.90 29-20
5.90
2.21
2-67
April...
14:60 21-20 10.80
3-33
3.24
May
4:20 17:20 246·00
8.78 262-70 27-99
34-18
June...
238.00 25.20
21-31
July
312.00 36.50
23.11
August September October
312-00 44-20
16.79
312.00 44.90
11:41
312.00 36·00
6.21
November
312.00 34.80
2:30
December
905-00 43-00 11:00
5.64
11.00
1.95
1.95
(January
273-00 47.00
3.90
7:50
0.52
February
229.00 45-00
2:00
1·60
1.25
March
186-00 54-80
-20
Nil.
3·90
April...
731-00 48-50
81.50
7-03
11-59
May
June...
164.00 49-20 64-20 179.00 58-00
744
8.57
191.00
5.55 342-60 34-38
60-21
July
August September October November December
312:00 43-70
312:00
50-20
10-78
12:09
312.00 42.30
7:00
312.00 55.30
0.02
281-00 59-50 14:50 236.00 60.00 129-50
42.65 253.90
0.34
144-00
0-51
0.85
1892.
1891.
Loss by Evaporation and Percolation
1,158-14
10-30
1,147-84
Total Rainfall during period of observation, 173-67 inches. Total Water collected was 1,14784 millions of gallons. Average Water collected per inch of rainfall, 6-63 millions of gallons. Percentage available for use, 42 per cent.
173-67
690
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