CATCHMENT CONTROL Whirinaki scheme first under revised policy

Press, Volume CXIV, Issue 33521, 30 April 1974, Page 15

CATCHMENT CONTROL Whirinaki scheme first under revised policy

The first catchment control scheme to be comprehensively planned in terms of the latest revision in Soil Conservation and Rivers Control Council policy has been approved in principle by the Government.

The initial phase of the Waikato Valley Authority’s Whirinaki catchment control scheme is estimated to cost $138,000 on a $3-to-$l Government subsidy. As an added incentive to encourage this kind of catchment planning elsewhere, the local share of the cost will be met by a further subsidy of up to a half.

The director of the Water and Soil Division of the Ministry of Works, Mr A. W. Gibson, said that the Soil Conservation and Rivers Control Council progress review had brought the recommendation that a catchment scheme be planned in its entirety.

Whirinaki was an excellent example of total catchment planning, and the rate of Government subsidy indicated it to be of national importance. The Waikato Valley Authority could also proceed with planning in detail for the remaining sections of the catchment, Mr Gibson said. The 56,000-acre Whirinaki catchment, in the Rotorua county, drains southward from its headwaters eight

miles south of the city, discharging into Lake Ohakuri. Transition from scrub and forest to grass on erosionprone ash showers has upset the balance of nature that previously existed and the outcome has been serious gully and stream bank erosion that has either threatened or eliminated areas of productive land. LOSS OF RESOURCES

Off-site effects have been accelerated silting, causing lake enrichment and the loss of recreational and wildlife resources. In some parts of the catchment land is not being used according to its capability, and this also has had detrimental effects. The scheme has been designed to proceed in five stages, beginning with the Rotohouhou subcatchment in the headwaters and continuing to the Totara and Rehi subcatchment, Mangatete and Fraser subcatchments, the balance of the eastern catchment and finally, the lake shore of the Whirinaki area —defined as being the land involved in hydro-power development. The proposed works fall into two categories, the first being water-way protection requiring standard double fencing and the retirement of primary water-ways, medium bank protection through the use of netting structures, associated pole and stake planting to counter severe bank erosion, and spaced pole planting. The second consideration is for hillside protection through

close and open planting with poles of conifers, and the securing of existing native forest. OWN ACT Whereas works of this nature would normally be sanctioned by the Soil Conservation and Rivers Control Council, the Waikato Valley Authority functions under its own act and its proposals are approved by the Minister of Works, or within the Ministry of Works under delegated authority. Mr Gibson said that recognition of the magnitude of soil erosion problems caused through soil and rock types of volcanic origin had been given emphasis only in the last 10 to 15 years, although erosion was evident long before this.

“The pumice plateau of the central North Island supports significant proportions of New Zealand’s agricultural, forest, industrial, recreational and urban-based investments,” he said. “As such, the region contributes a great deal to national prosperity. It is no more than sound management to encourage measures to protect, enhance and sustain the land resource on which these industries—and the communities supporting them—are dependent.

“In the national context, the volcanic plateau of the central North Island requires maximum local soil conservation assistance if the benefits from the region to the nation are to be maintained,” Mr Gibson said.