198 



Report of the Commissioners on the 



But it may be objected that the great body of the flood- 

 water will so spread over the land and flow past that the 

 aqueduct cannot catch its proportion of it, this may be 

 I^revented by the construction of a low dam of an inexpensive 

 character. 



We hence affirm that the aqueduct, with slight additions 

 to its lower bank, will be capable of conveying 31,831^648 

 cubic yards per annum into the reservoir, with a maximum 

 delivery in time of floods, of 1,935,999 cubic yards in twenty- 

 four hours, being half the assumed amount discharged by 

 the Plenty after a rainfall of one inch within twenty-foui: 

 hours. 



Having thus determined the total amount that can be de- 

 livered into the reservoir from the Eiver Plenty, our next 

 subject of inquiry is relative to that derivable from the 

 drainage basin of the reservoir, and also from the rainfall 

 upon its surface, both of which can be arrived at from the * 

 data already determined on. 



The area of the drainage basin of reservoir is 3,000 acres, 

 or 14,520,000 square yards, obtained from Government sur- 

 veys, a rainMl of 31 inches on which will equal 12,503,333 

 cubic yards; then the amount due to 17-856 inches loss from 

 surface evaporation, as before determined, must be deducted, 

 equal to 7,201,324 cubic yards, leaving 5,302,009 cubic yards 

 derived from surface drainage into reservoir. 



The area of the reservoir itself is 1,460 acres, equal to 

 7,066,400 square yards; hence 31 inches rainfall on the area 

 would equal 6,084,955 cubic yards. 



Hence the different amounts of supply ,to the reservoir 

 will stand thus : — 



Supply derivaMc from the Kiver Plenty ... 31,831,648 cubic yards. 

 Supply derivable from drainage area of 



basin of reservoir 5,302,009 do. 



Supply derivable from rainfall of 31 inches 



on surface of reservoir 6,084,955 do. 



Total in reservoir 43,218,612 cubic yards. 



This amount, as delivered into the reservoir, is subject to 

 the further loss of evaporation from its surface, already de- 

 termined at 9 feet of depth for still water, which, over a sur- 

 face of 7,066,400 square yards, will give 21,199,200 cube 

 yards to be deducted from the last amount^ leaving 22,019,412 

 cube yards in reservoir. 



