The Effects of Spatial and Temporal Variations in Forest Structure on Snow
Accumulation and Melt
Objectives
The objective of this study is to quantify differences in snow accumulation and
melt under diverse forest cover conditions, and to examine how forest cover and
landscape position influence snowmelt contributions to the hydrograph.
Measurements are being made at various locations in the Upper Penticton Creek
study area to:
- quantify spatial and temporal variability in snow accumulation and melt
under several different forest canopy conditions
- develop a predictive tool which can be used to evaluate potential
changes in snow accumulation and melt associated with changes in forest
stand structure, in association with snow survey sites at other locations,
and
- determine how snowmelt over the landscape contributes to the hydrograph
at the base of the watershed and the effects of logging on runoff
synchronisation or desynchronisation.
The results of this research will improve our understanding of snowmelt
runoff generation in small interior watersheds and will improve operation
planning guidelines under B.C.'s Forest Practices Code.
The Effects of Forest Harvesting on Water Quantity and Quality in Small
Interior Watersheds
Objectives
One of the primary long-term objectives of the Upper Penticton Creek Watershed
Experiment is to quanity the effects of increasing levels of forest development
on water quality and quality. More specifically, to:
- measure any detectable changes in the hydrograph, including peak, low,
and annual flows, resulting from logging over 10%, 20%, and 30% or more of
small, headwater basins typical of south-central British Columbia, and to
- measure any detectable changes in water quality resulting from
increasing rates of logging and associated forestry-related activities,
including road construction, silviculture, and cattle grazing, from small,
headwater basins.
The results of this research will improve our understanding of
forestry-related effects on water supplies from headwater streams in
south-central British Columbia, including quantity, timing of flow, and quality.
The results will also be used to improve forest management guidelines under
B.C.'s Forest Practices Code.
Influences of Timber Harvesting and Road Construction on the Sediment Budget
Objectives
This project investigates the effects of timber harvesting and road construction
on physical water quality in small, high elevation interior watersheds. Specific
objectives include:
- providing long-term physical water quality data for the Upper Penticton
Creek study streams, and
- quantifying the effects of forest development on erosion, sediment
delivery to stream channels, and on channel morphology in 240, 241, and
Dennis Creeks.
The results will be used to develop forest practices guidelines that minimise
sediment generation and channel change resulting from development.
Effects of Road Construction and Timber Harvesting on Stream Invertebrate
Communities Collected from Logged and Un-logged Streams, using Artificial
Substrate Sampling
Objectives
The major objective of this study is to determine if the forest harvesting
techniques in the Upper Penticton Creek Watershed have an impact on the aquatic
invertebrates in the streams draining the watershed. More specifically,
the comparison of logged and control streams in this study will examine the
following:
- Identify animals living in these high altitude, low order streams. This
information will provide a baseline for investigating the effects of road
construction and harvesting on streams.
- Identify indicator species that are sensitive to the effects of
harvesting practices.
- Examine changes in the biodiversity of aquatic invertebrates in these
streams.
- Examine changes in the distribution of the functional feeding groups of
invertebrates in the streams. A change in these feeding groups may indicate
a change in the type of organic matter inputs to the streams, and in the way
that organic matter is processed.
This information will tell us if the streams are still healthy, as aquatic
invertebrates are excellent indicators of water quality, and are also important
food items for fishes.
Terrain and Soils of the Penticton Creek Watershed
Geology:
The study area is located in the Okanagan Highlands physiographic region of
British Columbia. Bedrock types underlying the area are predominately coarse
grained plutonic rocks, mainly granite and granodiorite, and granitic gneisses.
All rocks are hard and competent, with distinct structures that have given rise
to rockfalls and rockslides in the upper elevations of the watersheds.
Terrain: Surficial deposits in all three catchments are dominantly glacial till
(morainal material) derived from the granitic rocks. On the upper slopes these
till deposits are shallow, and exposed bedrock and large glacial erratics are
common. The deposits on mid and lower slopes have deposits that are over two
metres deep. Small areas of colluvium are interspersed among the till deposits.
Glaciofluvial terraces and blankets occupy some of the lower slopes of the three
catchments. Narrow areas of more recent fluvial floodplain deposits and organic
wetlands occur along the main creeks.
Soils:
The soil types mapped in the three watersheds have been primarily differentiated
by parent materials and soil depth, with further subdivisions based on wetness
(soil drainage).
Soils developed on glacial till (units 2, 2w, 2s, 2vs, 2d) cover approximately
80 – 90 % of the three catchments. Their surface soils typically are coarse
sandy loam-textured and subsoils are generally loamy sand in texture and
slightly compacted at depths below 60 cm. All soil horizons have low clay
content and are very gravelly, cobbly and stony. Forest floors are generally
very thin (less than 4cm thick).
Soils developing on glaciofluvial materials (units 3, 3w, 3d) occupy
approximately 10% of 240 and 241 Creeks, and a very minor component of Dennis
Creek. Surface soil textures are typically sandy loam with a low clay
content. The subsoil is often loamy sand textured, although layers of sandy loam
or sand can occur in the soil profile. These soils are often only distinguished
from till-derived soils by the absence of slightly compacted horizons. All soil
horizons are usually very gravelly and cobbly and forest floors are generally
very thin.
The soils developed on recent fluvial (or flood) deposits are intermingled with
small areas of organic deposits (units 3, 3w, 4). The size of individual organic
wetlands usually does not exceed 0.1 ha. Glaciofluvial or morainal deposits
generally underlie these recent materials at depths that vary from 30 cm to over
one metre. Surface soil textures are typically organic-rich silt loam and fine
sandy loam, or moderately decomposed organic layers in the wetlands.
Subsoils are often sandy loam and loamy sand textured, although layers of silt
loam or sand do occur in the soil profile. Forest floors vary considerably in
thickness.
The predominant soils (units 2 and 3) are rapidly pervious, have high hydraulic
conductivity, and have low water holding capacity, They are generally well or
rapidly drained. Areas that receive permanent or intermittent seepage on
the lower slopes are generally moderately well drained, except for the fluvial
–wetland complexes which are poorly and very poorly drained.
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Effect of forest canopies on the energy available for snow melt and summer
evapotranspiration
Objectives
Provide a high quality climate station network to support long-term hydrologic
studies in the Upper Penticton Creek Watershed Experiment.
- Describe microclimate changes resulting from harvesting.
- Quantify changes in rainfall reaching the soil as a result of forest
harvesting.
- Quantify changes in the rate of snow melt as a result of harvesting.
- Quantify changes in the amount of water available for drainage as a
result of forest harvesting.
- Quantify evapotranspiration rates from high elevation vegetation.
Develop and test an improved snow melt prediction model.
- Apply existing models to determine radiation below canopies and in small
openings.
When completed, the first five year portion (up to the 20% rate of cut) of
the Upper Penticton Creek Watershed Experiment will provide: 1) data to support
or improve upon watershed related regulations and guidelines, 2) an improved
understanding of basic hydrologic processes in the south central interior, and
3) improved tools for predicting forest harvesting related hydrologic impacts.
The data collected annually as part of this specific project, are also
necessary for other component projects of the Upper Penticton Creek Watershed
Experiment.
Watershed Scale Hydrologic Modeling
Objective
The overriding goal of the hydrologic modeling research in the Upper Penticton
Experimental Watersheds is to develop a forest management decision-support tool
that can be used in guiding best management practices from the perspective of
minimising the risk of increased peak streamflows and surface erosion.
Strategy
Towards our goal of developing a decision-support tool, we are using long-term
computer simulations spanning periods of several decades. Forest management
impacts on streamflow will be quantified through an analysis of pre- and
post-logging watershed conditions. We have identified the following research
tasks to achieve our objectives: (1) Prepare data, and develop and calibrate
numerical models for each of the candidate watersheds. (2) Develop long-term
proxy climate data sets for each of the candidate watersheds, (3) Develop forest
harvesting and road scenarios for the watersheds. (4) Develop a vegetation
database considering forest regrowth for each of the watersheds (5) Perform
long-term pre- and post-logging simulations using the proxy climate data sets,
management scenarios and regrowth parameters. Determine logging impacts on
streamflow characteristics using DHSVM. (6) Compare model-predicted watershed
impacts with index calculations regarding peak flow in the Watershed Assessment
Procedures and provide suggestions for augmenting, improving and/or adapting
some of the guidelines. (7) Compare model-predicted watershed impacts to natural
variability in watershed processes under pre-logging conditions and provide
suggestions for developing thresholds that establish the significance of logging
related changes in watershed hydrology as compared to natural variability in
watershed processes. (8) Analyze and compare the forest management impacts to
develop decision-support tool.
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For more information about the Upper Penticton Creek Watershed Experiment,
please contact:
Rita Winkler, Research Hydrologist
Ministry of Forests and Range
Southern Interior Forest Region
515 Columbia Street
Kamloops, B.C., V2C 2T7
Canada
(250) 828-4169
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