New Zealand Journal of Marine and Freshwater Research abstracts
New Zealand's National River Water Quality Network
2. Relationships between physico-chemical data and environmental
factors
RUURD MAASDAM
Water Authority Friesland
P. O. Box 36
8900 AA Leeuwarden
The Netherlands
DAVID G. SMITH
NIWA-Ecosystems*
National Institute of Water and Atmospheric
Research Ltd
P. O. Box 11-115
Hamilton, New Zealand
Abstract The first 2 years' physico-chemical data from the
National River Water Quality Network's 77 river and stream sites were related
to environmental variables such as catchment erosion, soil and rock types, and
land use. Multivariate analysis reduced the physico-chemical data to seven
groups of determinands: major ions (as indexed by conductivity), P species (DRP
and TP), N species (TN and NO3-N), "organics" (BOD5 and NH4-N), clarity,
absorption coefficient (
g440), and a combination of DO and pH. The river
sites were grouped into nine clusters using these seven determinand groups; 65
sites (containing the most pristine waters, a majority of which are located in
the South Island) were contained in just four clusters. Differences between the
clusters are best explained by the concentrations of P species and "organics".
Discriminant analysis was used to relate the physico-chemical site clustering
to environmental variables; it indicated that the degree of pasture development
and its associated variables (e.g., negligible to moderate erosion, high mean
annual water temperature, high percentage recent soils, low mean catchment
elevation) are the most important factors affecting water quality.
Keywords water quality, rivers, environmental variables,
multivariate analysis
PDF file of entire paper: medium quality (1404K); (scanned from paper original: notes about this process)
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