SILTING OF RIVER

Poverty Bay Herald, Volume LXIV, Issue 19375, 13 July 1937, Page 4

SILTING OF RIVER

LEVEL OF THE WAIKATO SURVEYS BY DEPARTMENT EFFECTS FROM ARAPUNI Sections of fertile pasture adjoining the lower reaches of the Waikato River are said to have been-trans-formed into patches of niggerhead and rushes on account of a rise in the river level, due to silting. Concerned by the area of the land which has been despoiled, settlers have several times made representations to the Government in an endeavour to have the lowering of the level carried out by the Public Works Department as a national undertaking.

As early as 1921 the magnitude of such a task was pointed out when the report of the Auckland Canals and Inland Waterways Commission was presented, and point was made of the major problem involved in any attempt to improve the scouring effect of the river, even for the limited purpose of improvement of navigation. However, between 1928 and 1932 the Public Works Department made extensive surveys of cross-sections of the river between Huntly and Kaiwaka Island, below Tuakau. Higher Summer Level Mr. J. Wood. Engineer-in-Chief and Under-Secretary to the department, explained that these observations were compared with a series of investigations made by the Lands Department between 1913 and 1915 and, from these- surveys and from information supplied by settlers, the fact had emerged that over a period of 30 years up to 1932 the low summer level of the river had not been raised by more than 12in. to 18in.

Observations also showed that the bulk of the silting, which is regarded as the main cause of the raising of the low summer level, took place in the vears immediately following the diversion of the Waikato River at Arapuni in 1928. At the same time, it was apparent that the bulk of the spoil thrown into the river at Arapuni was eventually transported to Maioro Bay, at the river mouth, and no evidence was obtained that permanent silting due to this cause woul4 result. No Scheme Proposed Discussing these contentions, Mr. Wood also pointed out that the construction of the Arapuni dam and the formation of the Arapuni lake would trap all the sands and silt brought into the river between ' Lake Taupo and the dam, a distance of 93 miles. This was an important factor, as it meant that the burden of spoil that the river below Arapuni' had to carry was substantially reduced, and it was better able to keep itself clear.

Inquiries reveal that there is no scheme proposed by the department for dealing with siltation. Authorities consider that to endeavour to promote scour for enlarging the channel generally is virtually impracticable.