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Approximately 90% of south-central British Columbia's domestic and irrigation
water originates in upland forested watersheds. These watersheds also
supply timber, cattle range, minerals and recreational opportunities. The
continuous supply of high-quality water, and the effects of changes in land use
on this resource, are of concern to land managers and water users alike.
Three small watersheds, tributary to Penticton Creek, were set aside in 1982 for
long-term study. The objectives of this study are to improve our
understanding of how forest land use affects streams, aquatic organisms,
streamflow, and water quality. The Upper Penticton Creek Watershed
Experiment is a collaborative effort of the British Columbia (B.C.) Ministry of
Forests, the B.C. Ministry of Water, Land and Air Protection, the B.C. Ministry
of Sustainable Resource Management, the City of Penticton, the Okanagan
University College, the University College of the Cariboo, the University of
British Columbia, the Water Survey of Canada, and Weyerhaeuser Company Ltd.
The watersheds included in the Upper
Penticton Creek Watershed Experiment drain into 240, 241 and Dennis Creeks,
located 26 kilometres northeast of Penticton, B.C. Each watershed covers
an area of approximately five square kilometres and an elevation range of 1600
meters to 2100 meters.
The predominant forest cover type over the 240 and 241 Cr. watersheds is
lodgepole pine (Pinus contorta Dougl.), whereas forests in the Dennis
Cr. watershed are dominated by Engelmann spruce (Picea engelmannii
Parry) and sub alpine fir (Abies lasiocarpa (Hook.) Nutt). Trees in the
study area are over 100 years old and reach a maximum height of 20 to 26 m.
Stands of lodgepole pine are evenly spaced, whereas spruce-fir stands generally
have a more clumped distribution of stems. Canopy densities vary from 35 to 50%.
Soil textures over the study area are coarse sandy-loam over loamy-sand. The
soils are derived from glacial-tills and coarse-grained granitic rocks. All soil
horizons are low in clay and high in coarse fragments. These soils have a low
water holding capacity and are well or rapidly drained. The forest floor is
generally less than 4 cm thick.
The mean annual precipitation is 750 mm, approximately half of which falls as
snow. By late winter, the snow pack is 1 to 1.5 m deep depending on forest
cover, the year, and location in the watershed. Snow water equivalents
measured on April 1st average 265 mm, and snowmelt from mid-April through June
averages 5 mm/d. On average, 380 mm of rain falls on the watersheds from late
May through October each year. Winter air temperatures occasionally drop to -20
C and in summer, daytime high temperatures occasionally reach the upper 20's.
Approximately 0.8 to 3 million cubic metres of water flow from each study
watershed annually. The highest daily flows occur in May during mid- to
high-elevation snowmelt and may reach 1.5 m3/s. The study streams do not
completely dry up at the gauge-sites at any time of the year. However, flows in
August through April are often less than 0.01 m3/s, one-hundredth of the
maximum. Late season streamflows are sustained by groundwater and rain.
The water quality in all study streams is generally high. Over the period 1992
to 2001, concentrations of nitrate plus nitrite nitrogen and phosphorus were
low, varying from undetectable to 0.42 mg/L and from undetectable to 0.32 mg/L,
respectively. Pre-treatment sediment concentrations fluctuated with streamflow
but did not exceed 20 mg/L of water and were most frequently lower than 5. The
water in all three creeks is highly coloured, with TCU varying from 0 to 70.
Water temperatures in the study streams range from just above 0 C in late fall
through spring to an hourly maximum of 25 C in summer, and average 9 C during
the snow-free season. The aquatic invertebrate community of both 240 and 241 Cr.
is dominated by Diptera (primarily chironomids).
The Upper Penticton Creek Watershed Experiment follows a
paired-watershed design in which one
watershed remains the undisturbed control throughout the experiment. Hydrometric
monitoring began in all three watersheds 10 years prior to development and has
continued through- and post- logging. Based on the calibration period data, the
240 Cr. watershed was designated as the control watershed and the 241 and Dennis
Cr. watersheds as the treatment areas.
Logging is being carried out in stages so that the effects of increasing levels
of cut can be studied. Conventional, clearcut logging techniques, to community
watershed standards, are being used in this experiment. All openings created by
logging will be site prepared and replanted, and roads will be deactivated, in
accordance with the Forest Practices Code.
Forest development began in the fall of
1995. Roads were constructed and limited areas logged. By the spring of 1996,
forest cover had been removed from 4% and 8% of the 241 and Dennis Creek
watersheds, respectively. The effects of this development on water quantity,
quality, stream channels, and aquatic organisms were monitored for three years.
A second logging-pass was completed during the winter of 1998/99, increasing the
open area to 17% and 29% of the two watersheds. Widespread insect damage
resulted in extensive logging over more than 50% of the Dennis Creek watershed
in late 2000. The area cut in the 241 Creek watershed has remained at 17% and
additional logging is scheduled for the winter of 2003.
Streams, streamflow, water quality, aquatic life, environmental conditions, snow
and forest characteristics will be monitored throughout the experiment; prior to
and during logging, and as the forest regrows. Through the diversity of
research and breadth of collaboration in the Upper Penticton Creek Watershed
Experiment, this endeavor provides an excellent opportunity for scientific
discovery as well as a forum for improved communication between researchers,
land managers, students of the natural sciences and the public. The
research results obtained at Upper Penticton Creek will contribute to a sound
scientific base for improved watershed management in British Columbia.
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