291
OK ENGINEERING FORMULÆ.
Ibhigation in India.
PiioroitpoN ok Rainfall kubninq off into Ouhaixs.
(From obsprvalions at Nagpur by A. Binnie.)
^falMnches111' f 1 6'77 19,4'?l29-r9l31-29|39*28*43-65'53’72
-wi -lal .Maj „I .Mj J...
In Mysore the proportion running ofif is assumed at • 25.
Loss of Water in- Tanks in Rajputana (Culcheth).
By Evapora- tion. By Ab- sorption, Ac. Total.
Day«. October to March, 182 .. .. April to June, 91 .. .. July to September, 92 .. .. Total 365 ,. .. Average per day .. .. feet », » .. inches feet. 2'32 2’24 1-59 6 15 •017 •202 feet. •75 1'34 1-53 3-Ö2 -01 •119 feet. 3 07 3-58 3-12 9-,7*7 •027 •321
In the Deccan the loss by evaporation, absorption, leakage,
&c., from October to March was found to be 3-51 feet in
182 days — -0193 feet per day. From April to May 2’U3 feet
in 61 days = • 0333 feet per day.
Loss by Evaporation only, in Feet.
Oct. ; Nov. j Dec. Jan. Feb. Mar. Apr. May. Total 8 Mon.
Rajputana •49 1-35 -29 •29 •35 •55 •73 •81 3’86
Bombay •65 |-49 -37 •44 •34 •44 •69 ■99 4-41
Nagpur ■50 -42 ’37 •33 •32 •48 ■76 •59 3-77
Or an average of '016 feet= -198 per day.
From observations Mr. Binnie deduces the following rule :■*-
If the average annual rainfall = WO, the minimum will equal
about -65; maximum about 1'40; and the average of three
consecutive dry years ■ 83.
Dutt of Water in Irrigation.
A constant flow of 1 cubic foot per second will irrigate the
following acreage. Tanjore, rice 44 acres; Mysore, rice in
ordinary soil, 30; in black cotton soil, 35; Sind, rice, 40;
Bombay (Deccan), rice, 40; sugar-cane, 100; ordinary winter
croppi, 150; 6 and 8 month crops, 150 j Aluuüooii crops
(usually grown without irrigation). 200.
u 2 .