98 Transactions.— Miscellaneous. 
water as one at the Taieri Lake. It is at this place, then, the Styx, that 
the natural advantages which exist should be utilized by the forming of a 
main reservoir. Here a large plain, 1800 feet above sea-level, and nearly 
flat, is narrowed in to a few chains width by the surrounding ridges, which 
thus offer a natural dam, only requiring man’s work to complete it. There 
is a choice of two sites one mile apart. For nine miles up this plain the 
total fall on the river does not exceed 40 feet, while the first six miles of 
this distance, I estimate, has not a greater fall than 10 feet. There is 
a great width on this plain, which naturally divides itself into 
two parts, 920 acres in the lower, and 5,344 acres in the upper, oF 
6,272 acres of water-space for the reservoir all over. The average 
depth of water, deduced by me from a few levels taken during the triangu- 
lation of the Serpentine Flat, are, for the lower area, 27°5 feet, and for the 
upper area 14 feet, taking the height of the embankment, or dam, at 30 or 
33 feet. The capacity of this reservoir will thus be 4,370,636,160 cubic 
feet, assuming the above figures as correct; and the cost of the dam, 5 
chains long, if of masonry, £6890. Now, from the Flood Commissioners’ 
report, I find they calculate on having to impound above the township of 
Outram, 1,506,400,000 cubic feet daily, while Mr. G. M. Barr’s paper gives 
4,608,000,000 cubic feet; and a rainfall of 1°5 inches run off over 1700 
square miles gives 4,233,968,640 cubic feet daily. The mean of these 
quantities, or 3,449,456,213 cubic feet, I take as the amount required to be 
impounded above Outram in one day, and as the duration of flood is found 
to be from seventeen and a half hours to three days the proposed reservoir 
has the necessary capacity.. For, as the drainage area above the Taieri 
Lake, compared with that above Outram, is as 850 square miles to 1700, 
the quantity of water to be retained at the Styx, taking it as the same with 
that at Taieri Lake, will only amount to 1,725,000,000 cubic feet. So that 
the Styx reservoir will be far more than equal to the work of retaining this 
quantity—or it will hold two and a half days’ accumulation at the rate of 
1725 millions of cubic feet per diem. 
The only doubtful element in the above is, does the catchment area above 
the proposed Styx reservoir run off daily this quantity—1,725 millions of 
cubic feet of water during flood? This can be ascertained approximately 
by experiment, and, should it be somewhat less, still the quantity would be 
large enough when retained by the reservoir, to afford an immense relief to 
the Lower Taieri Plain. 
Deep Stream Reservoir. 
Supplementary to that at the Styx, a reservoir or reservoirs on the Deep 
Stream would be very useful. A good site exists for a dam to one of these, 
about a mile and a half below Walsh’s accommodation house, where 42 
