260 



The north-west wind, especially if accompanied with a warm drizzling rain, 

 has a very marked effect on this class of rivers. At such times, the Dart, 

 Matukituki, and such like, become rivers of half a mile wide, and of course 

 pour into the lakes vast quantities of water. The valleys on the west side of 

 Te Anau and Manipori Lakes being generally very narrow, the vertical rise 

 and fall of their rivers is quite astonishing. In many of them, unmistakable 

 flood-marks show that this is not less than 20 feet. The actual observation of 

 these facts impresses the mind very forcibly with the value of the lakes as great 

 regulating reservoirs for the Clutlia and Waiau Rivers. The Clutha has 237 

 square miles of lake to regulate its flow, and the Waiau 198 square miles, or, 

 altogether, an area of 435 square miles for the two rivers. This surface, like 

 a great compensating balance, is ever in a state of oscillation up and down 

 between the inflow and outflow of the rivers. Bvit it attains its maximum 

 level for the year in January or February, and its minimum in July or 

 Augvist. The vertical range of lake surface varies in different years, and the 

 lakes have also differences depending on their area and supply. Generally, 

 the range may be stated at from four to nine feet. 



In the season of 1865-66, the Wakatipu Lake had a range of no less than 

 ten feet. On the 14th January it attained its highest level, the water standing 

 two feet deep in Rees-street, Queenstown. The lake had probably not been at 

 so high a level for a very long time before, for trees of two and three feet in 

 diameter were sapped by the rising waters, and laid prostrate on the margin 

 of the lake. A cold spiing preceded this great flood, and the lake was then 

 nine inches lower than it has ever been known to be before or since. 

 Consequent on this coldness, more snow than usual was reserved for the 

 melting of the summer sun. The lake had reached a high level, when three 

 days of warm wind from the north and north-west, accompanied with rain, 

 raised its surface to the highest observed level. 



The fact of the lowest and highest levels occui-ring in the spring and 

 summer of the same season, and so intimately connected with change of 

 temperature, is an evidence of the value of our equable insular climate in the 

 river system of the country. For with the same temperature, but colder in 

 winter and warmer ixi summer, the glacial-fed rivers would become still moi-e 

 fluctuating ; and such rivers as the Mataura and Taieri, that have their 

 principal sources in high snow-clad mountains, and have no lakes worth 

 mention to regulate their flow, would necessarily become much more irregular 

 in volume than they are under present conditions. 



The ordinary condition of a glacial river, such as the Dart, is a rapid 

 stream of three or four chains wide, and from three to four feet deep, with a 

 number of smaller branches running out and into each other as they continue 

 their course along the channel, which is a wide waste of shingle and quicksand, 

 at places a mile bi-oad. This matter is carried forward to the lakes, and by 



