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2. Profile

The profile includes the background information about natural conditions and human activities. The sections on morphology, soils, and vegetation include information about the physical and chemical properties of each compartment from background literature. The climate information is from Capital Regional District monitoring station at Sooke Lake. The anthropogenic information is based primarily on information from the Water Allocation Plan and the Local Area Plan.

2.1 Morphology

The chemical signature of a region depends on a complex relationship between geology, soils, climate, ecology, and the movement between these compartments.

2.1.1 Geomorphology

Vancouver Island is comprised of a series of terranes, which are pieces of the earth's crust that upwelled from the floor of the Pacific Ocean, cooled and drifted eastward to collide with the west coast of North America (Yorath, 1995). The primary terranes from east to west (oldest to newest) include the Wrangellia Terrane, which accreted 100 million years ago (Mya); the Pacific Rim Terrane, which accreted 55 Mya; and, the Crescent Terrane, which accreted 42 Mya. The Pacific Rim Terrane includes both the Pacific Rim and the Leech River complex. The Crescent Terrane is south of the Pacific Rim Terrane at the boundary of the major Leech River fault.

Each terrane has characteristic bed rock types or groups. The Leech River Complex is comprised of metamorphosed sedimentary and volcanic rock - the strata consist of sandstone, chlorite schist, argillite, chert, and other rock types. The Crescent Terrane is comprised mainly of the Metchosin Igneous Complex - the strata consists of gabbro dykes and basaltic pillows, which are a feature of the Sooke Potholes Provincial Park.

The Metchosin Igneous Complex surrounds the Sooke Harbour and Basin lowlands (Tectonic Map, 1991). The plutonic and ultramafic rock groups identified on the map around the Sooke Basin include:

• ET gc: Catface: light coloured biotite-hornblende, locally porphyritic, granodiorite and tonalite or quartz diorite, dacite hornblende feldspar porphyry dykes
• ET dso: Sooke: layered gabbro overlain by a sheeted dyke complex (ET dsd)

Characteristic elements in these rock types include iron, aluminum, magnesium, potassium, calcium, sodium, and silica (Christopherson, 1997). A more detailed breakdown of the elemental composition of rocks and minerals described in this section is contained in Table 1.

A recent local study examines the mass balance and sink capacity of the Sooke Lake Reservoir, as published in a thesis, "The Geochemistry of Vancouver Island natural Waters. Case Study: Sooke Lake Reservoir" (Coneys, 1998). Coney's identifies three main rock types in the Sooke Watershed as Colquitz Gneiss, Wark Gneiss, and Schist.

In addition to the Leech River Complex and the Metchosin Igneous Complex, the Carmanah Group, which includes the Sooke Formation in the adds to the complex mosaic (Yorath, 1995). The Sooke Formation is comprised of calcium cemented sandstone formed 25 Mya in shallow marine waters. These sandstones are comprised of quartz, basalt fragments, feldspar, ilmenite, magnetite and concentrated deposits of fossil debris called coquina. The Sooke Formation also contains coarse pebble and boulder conglomerates.

2.1.2 Geomorphic Processes

Vancouver Island experienced three glacial periods and two inter-glacial intervals over the last two million years (Soil Landscapes, 1986). The most recent, the Fraser Glaciation period, began 30,000 years ago and the ice retreated 13,000 years ago to form the current coastline 10,000 years ago. Massive amounts of bedrock were moved during this glacial period as glacial drift, which includes glacial till, fluvioglacial, glaciolacustrine, and glaciomarine sediments deposited as surficial materials.

The combined surficial glacial deposits, colluvial deposits, and organic deposits form the parent materials that are the building blocks of the local soils (Jungen, 1985). There are five primary types of surficial deposits on Southern Vancouver Island. Colluvial deposits are materials that consist of mixed fragments of bedrock transported by gravity or mass wasting. Fluvial deposits are materials that consist of mixed fragments of bedrock, gravel, sand, and silt transported by flowing water. Marine deposits are materials that consist of fine sediment, sand, and gravel deposited in salt or brackish water bodies. Morainal deposits are materials that consist of sand, silt, clay, and coarse fragments of bedrock transported by glacial ice. Organic deposits are materials that consist of accumulations of local vegetation.

2.1.3 Soil Classification

The lower SRW contains primarily Soil Orders of Brunisols and Podzols and Great Groups of Dystric Brunisols and Humo-Ferric Podzols respectively (Soil Landscapes, 1986). More detailed classification includes soil associations based on the Soils of Southern Vancouver Island (Jungen, 1985). The classification of the soils and the soil associations are illustrated in Figure 4.

The soil parent materials and the soil forming processes determine the physical and chemical characteristics of the soil materials. These characteristics are summarized in Table 2.

In addition to soil classification at the level of soil Order and Great Group, the soils are classified by soil associations, which provides detailed information about the physical properties and characteristics of the soil as listed in Table 3. The Coastal Western Hemlock/Doug-fir sub-zone is a commonality for the soil associations listed in the lower SRW.

2.1.4 Climate

The climate is wet maritime with mild wet winters and warm dry summers. The average monthly precipitation for the thirty-year climate normals detailed in Table 4. This is based on the information from the Atmospheric Environmental Stations at Sooke Lake Reservoir and Sooke. The mean annual precipitation is 1265 mm to 1465 mm.

The mean temperature for the year is 9.1°C. The warmest month is August with a mean temperature of 14.2° and the coolest month is January with a mean temperature of 3.8°C (Jackson & Blecic, 1996). The average monthly temperatures for the study period and the precipitation normals are illustrated below in Figure 5.

2.1.5 Biogeomatic Classification

The biogeomatic classification of the study area is Coastal Western Hemlock (CWH) zone (Pojar, 1991). Western hemlock (Tsuga heterpphylla) and western redcedar (Thuja plicata) are the dominant forest cover species in undisturbed mature stands. Characteristic features also include a sparse herb layer and dominant moss species such as step moss (Hylocomium splendens) and lanky moss (Rhytidiadelphus loreus). Red Alder (Alnus rubra) is common in disturbed areas and black cottonwood (Poplus balsamifera) occurs on large rivers with floodplains. The lowest reach of the SRW on the flood plain has been cleared and is significantly disturbed with isolated stands of CWH mixed with deciduous trees and sections of shrubs.

The CWH typically regenerates where acidic humus accumulates on the forest floor. Soil processes include accumulation of acidic organic matter, leaching, eluviation, illuvation and gleying. The rapid addition of organic colloids and weathering of iron and aluminum offset heavy leaching. Heavy precipitation accelerates leaching of nutrients from the mineral soil. Soils derived from acidic parent materials such as granodiorites are poor in nutrients and the biomass contains the nutrients to maintain ecosystem productivity. Common soil associations include Humo-Ferric Podzols to Ferro-Humic Podzols (ibid).

As illustrated earlier, the lower SRW also contains soils of the Brunisol Order with Dystric Brunisols at the great group level (Soil Classifications, 1986). At the level of soil associations, the vegetation zone is Coastal Western Hemlock Zone with Coast Doug-Fir sub-zone (Jungen, 1985).

Email Judith Burke at Waterose Environmental Services

• Water Quality Tests Offered by Waterose

• Twelve Month Baseline Water Quality Study for Salmonids in the lower Sooke River Watershed (Victoria Times Colonist Enviro News)

• Twelve Month Baseline Water Quality Study for Salmonids in the lower Sooke River Watershed (Sooke Mirror)

• Water Quality Project on Musqueam Salmon Stream in Urban Vancouver

• Analysis of Coliforms and Nutrients in surface waters flowing into Esquimalt Lagoon

• Water Quality Monitoring on Ayum Creek, a wild salmon and trout bearing stream, for Society for the Protection of Ayum Creek and Fisheries and Oceans, Canada

• Testing the Waters Story in Sooke News Mirror, March 28, 2001 about the Automated Water Quality Monitoring Project

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