Carr, R.G. 1978 An investigation of contamination of the Wahianoa river, Tongariro power development. Lower Hutt: New Zealand Geological Survey. New Zealand Geological Survey report EG 300 18 p.
Abstract: Low pH values have been recorded for a number of years in the Wahianoa River, which flows off the southeastern flanks of Mt Ruapehu. Eruption debris from the Crater Lake are present in the upper catchment area and the contamination of the Wahianoa River waters is traced to these deposits. The river has low conductivity values, which indicates a low dissolved solid content. Poor buffering capacity and low acidity are also features of the water. Records show that contamination is released to the stream during periods of thawing, thus causing a drop in the pH over summer. However the degree of contamination at present is not serious as the inflow of small streams in the lower river quickly causes a return to normal pH values. Since the contamination is easily neutralised it is found that these waters should not present a danger to aquatic life when diverted to other catchments for the Tongariro Power Development. This favourable situation may change after large eruptions of Mt Ruapehu. (auth)