Opponents band together

Press, 27 December 1979, Page 13

Opponents band together

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SUE SHEPHERD

Opposition from environmental groups is not to irrigation as such, but to tne effect of reduced water flows on river ecology. The Rakaia River is acclaimed as the best salmon fishing river in New Zealand and each season draws tourists from al) over the world. It is also the habitat of two species oi birds unique to New Zealand — the wrybill plover, that breeds only on the braided channels of a few Canterbury rivers, and the black tern. 1 n Christchurch recently, 25 local environmental, wildlife, and recreational organisations representing more than 10,000 members, met to discuss the scheme. Interest and opposition is mounting as the public learn more of the effects reduced water flows will have on the river. At the meeting, these effects were discussed by representatives from acclimatisation societies, wildlife protection societies, canoe clubs, jetboat clubs, anglers, the Rakaia River Association Inc., game shooters, and workingmen’s clubs. The main objections were to the low flow level set at 42 cumecs by the North Canterbury Catchment Board’s water allocation plan. The plan was drafted in 1974. It sets a low flow level of 42 cubic metres per second (cumecs) on the river. Allocation of water was proportional to the river flow during the summer months. The percentage of water

allocated for irrigation when for example, the river flows are up to 142 cumecs, would be: October, 40 per cent; November to December 50 per cent; January. 40 per cent; February to March, 35 per cent. The low flow figure was calculated on flow recordings taken at the Rakaia Gorge — about 60 kilometres from the river mouth. Between the river mouth and the gorge, a minimum of 25 per cent of that water would be lost through evaporation and natural absorption, according to research by the University of Canterbury’s zoology department.

The allocation plan stated: “The real effect of a period of sustained flow in the Rakaia River could only be accurately measured when conditions wore experienced and a major irrigation scheme was in operation.” The plan would be subject to review at • such times as irrigation development, results of research into fishery’ requirements, or any major unforeseen factor affecting the resource should render the plan unacceptable for future management. Studies of the reduced river flow’s on existing schemes have raised questions about their effects on wildlife, fish, coastal erosion, and the balanced

ecology of the rivers. Dr R. M. Kirk, senior lecturer in geography at the University of Canterbury, details in an article the effects of reduced river flows on the river mouth and coast surrounding the Waitaki River. The reduced flows were a direct result of irrigation and hydro developments on the river since 1935. They caused coastal erosion, formation of a river mouth lagoon, and periodic closure of the river mouth, he says. Inadequate research on the environmental impact of the scheme and the effects of low flows on the river ecology and poor liaison from the M.W.D.

were criticised by the groups. The Rakaia River is a valuable asset as one of the few major braided east coast rivers still in a comparatively natural state, says Mr B, Cow’ie, from the University of Canterbury’s zoology department. Inadequate research has been carried out to show that water abstraction during the summer months would not be detrimental to the river's fauna. “We are concerned that unaturally’ low flows will have substantial effects on the minor braids of the river which are important habitats for food organisms, native fish, and migrating salmon smolts.” Substantially reducing

the river flows would therefore have severe effects on the tish life and fisheries value of the Rakaia River, Mr Cowie says. “We are worried that the 42 cumec minimum level at the gorge is insufficient to maintain present values in the river.” The zoology department is opposed to any change in the exploitation of the river and supports proposals for research into the effects of low flows. A revised plan could be considered in the light of adequate information at a later date Mr Cowie adds. “The onus is on the proposers of the scheme to demonstrate conclusively that it will not endanger the unique elements of the river,” says Mr T. N. D. Anderson, for the Christchurch branch of Friends of the Earth. A full social, economic, and environmental assessment of the effects of the scheme would need to show clear benefits to the region and the country, he adds. Friends of the Earth oppose any’ modification of the Rakaia River because of the need to protect the habitat of the wrybill plover, to maintain the character of the river, and the probable effect it would have on other’ bird and fish life. The organisation sought more research on the effects of water abstraction on the river, of the economics of the scheme, and of alternative schemes that could supply water.