New Zealand Journal of Marine and Freshwater Research abstracts
Water quality and thermal regime of the Motueka River: influences of
land cover, geology and position in the catchment
Roger G. Young
Aaron J. Quarterman
Cawthron Institute
Private Bag 2
Nelson, New Zealand
email roger.young@cawthron.org.nz
Rebekah F. Eyles
Department of Zoology
University of Otago
P.O. Box 56
Dunedin, New Zealand
Robert A. Smith
Tasman District Council
Private Bag 4
Richmond, New Zealand
William B. Bowden*
Landcare Research
P.O. Box 67
Lincoln, New Zealand
*Present address: School of Natural Resources, University
of Vermont, Burlington, VT05401, United States.
Abstract We examined the effects of land use, geology,
and longitudinal position within the river network on water quality and thermal
regime at 23 sites within the Motueka River catchment. The concentrations
of suspended solids, nitrate nitrogen, total nitrogen, Escherichia coli,
and Campylobacter were higher at sites draining pastoral and horticultural
land than in similar-sized native or plantation forest streams. Average daily
mean temperature and minimum temperature in summer and maximum winter temperature
were higher in unshaded pastoral and horticultural streams than at native
forest sites. Differences in water quality and thermal regime were also observed
among sites with contrasting geology. Conductivity, pH, and minimum winter
temperatures were highest at sites draining marble terrain. In contrast,
longitudinal patterns in water quality and temperature regime along the 120-km
length of the river were relatively weak, although longitudinal patterns
in amplitude of daily temperature fluctuation matched theoretical predictions.
In this study, differences in land use appeared to have the strongest influence
on most water quality and thermal variables examined. However, geology was
an important factor explaining variation in certain variables (e.g., pH and
conductivity). Longitudinal patterns in water quality and temperature were
relatively weak and in many instances were linked with longitudinal patterns
in land use and geology rather than catchment location alone.
Keywords water quality; temperature; thermal regime;
land use; agriculture; horticulture; forestry; geology; nutrients; sediment;
Escherichia coli; Campylobacter; conductivity
M04096; Online publication date 17 June 2005 Received 20 April 2004; accepted
13 December 2004
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
803-825
0028-8330/05/3904-0803 © The Royal Society of New Zealand 2005
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