New Zealand Journal of Marine and Freshwater Research abstracts

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Baseflow water chemisty in New Zealand rivers 2. Influence of environmental factors

MURRAY E. CLOSE

Ilam Research Centre
DSIR Geology and Geophysics
Department of Scientific and Industrial Research
P. O. Box 29 181, Christehurch, New Zealand

ROBERT J. DAVIES-COLLEY

Water Quality Centre
DSIR Marine and Freshwater
Department of Scientific and Industrial Research
P. O. Box 11115, Hamilton, New Zealand

Abstract Baseflow water chemistry in 96 New Zealand rivers was related to selected environmental variables quantifying lithology, land use, topography, and hydrology. The river sites were clustered using five water quality variables: major ions, phosphorus species, organic and nitrogen species, calcium, and nitrate. Eleven site clusters were identified and the differing water quality regimes discussed. The effect of the environmental factors on water quality was investigated using discriminant analysis. The resultant model assigned 73% of the sites to the correct cluster. The most important environmental variables determining water quality were hydrological variables such as specific yield, and proportional areas in the catchment of soft sedimentary rock, intensive pasture (which was negatively correlated with steep slopes and high altitudes), exotic forest, and volcanically derived rock. Multiple regression equations relating individual water quality determin-ands to these environmental variables were derived. All equations were highly significant (P < 0.0001) and R* values ranged from 0.65 to 0.83 for conductivity and major ion species, and from 0.46 to 0.70 for nitrogen and phosphorus species. These equations could be used to give a rough indication of likely water quality at unsampled sites which wouid be valuable in a variety of water management situations.

Keywords water quality; baseflow; environmental variables; clustering; discriminant analysis; multiple regression

New Zealand Journal of Marine and Freshwater Research, 1990, Vol. 24: 343-356 Crown copyright 1990
Received 29 March 1990; accepted 20 July 1990

PDF file of entire paper: medium quality (1054K); (scanned from paper original: notes about this process)

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