98 Trajisactions. — Misceitaneous, 



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, or 

 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, £6390. 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 di-ainage 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 rehef 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 an 



