Evidences of Distribution of Rainfall.
And what do we find to be the case? The experience of the oldest settlers on the Upper Taieri Plains goes to show that the above theory is correct. For instance, Mr. James Murison, who first took up country there as a runholder in 1857, has assured me that, while the southerly storms rage around the Lammerlaw and Rock and Pillar, the basin of the Upper Taieri River itself escapes these to a great extent. From the Kyeburn, all round the north and west side of the plain to the Totara, that is over an area of 280 square miles, or 180,000 acres, there is not a single stream but such as a man may easily jump across. The Kyeburn stream has a rapid descent, and in floods rises to a considerable height, but falls quickly. This I saw during the big flood of 1868, when camped on its banks. The streams then round to the Totara discharge very little rainfall into the Taieri; and the most received by Mount Ida flows into the Waitaki; while on the east side, round to Hyde, there is but a small quantity runs down the Sowburn and Pigburn.* But the Deep Stream and Lee Stream rise rapidly and carry off as swiftly a large amount of rainfall. After the flood of February, 1877, I examined parts of the gorge of the Lee Stream, where the flood marks were visible 40 feet above the ordinary water-level on a width of about two to three chains. This gorge has a descent of 900 feet in 11½ miles, while that of the Deep Stream falls 825 feet in 20 miles, or thereby. Then it is well known the main body of the Taieri above the Styx comes away slowly—owing partly, no doubt, to the sponge-like and retentive nature of its catchment ground, and continues high long after the Kyeburn, Deep Stream, and Lee Stream have run off their flood waters. These latter streams are sudden and violent in their action, especially the Deep Stream, which should be checked; but most danger appears to me to lie in the accumulation of rainfall at the sources of the Taieri itself, after the ground there has become saturated and the river has risen to its full capacity. Here, then, the main reservoir should be.
[Footnote] * I find from measurements recently made by Mr. D. Barron, that the average discharge at Hamilton Bridge exceeds that at Pateroa Ford by only 8,000,000 cubic feet daily.
Stated shortly, the above remarks come to this,—That an excess above the average rainfall on the basin of the Taieri River takes place on and around the Lammerlaw Mountains; that the Sutton, Deep Stream, Lee Stream, and Waipori River, carry off the first of this rainfall, while the Upper Taieri River itself brings away the main flood comparatively slowly after-wards; and that on these streams the necessary sites for impounding reservoirs must be looked for.