The Salmon River watershed is at the rural-urban fringe of the rapidly developing
Greater Vancouver Regional District (GVRD) and has undergone substantial land-use change
in the last 20 years. This study provides information on spatial and temporal patterns of
water quality within the Salmon River, using trace metals in sediments, and nitrate and total
phosphorus in water as indicators of the quality of the aquatic environment. Relationships
between water quality, surficial materials, and land use within the watershed are examined
using a watershed approach combined with GIS techniques.
Approximately 80 km² in size, the watershed areas’s land is 50% agricultural, 7%
residential, and 25% undeveloped. The glacial outwash deposits in the middle reaches of
the river make up the Hopington Aquifer, which is an important source of ground-water
supply and baseflow during the low flow period of July through September.
The trace-metal concentrations in fine-fraction (<63 μm) sediments from 19 sites
within the stream system were compared with the background metal concentration in
surficial materials from within the watershed. No evidence was found of elevated total
metal concentrations in sediments for the metals Zn, Cr, Cu, Co, Ni, and Mn. At the
stations on the glacial outwash parent materials, NO₃-N, specific conductance, and chloride
increase in the downstream direction, and are likely due to anthropogenic additions. The
difference in specific conductance, chloride, NO₃-N, and total phosphorus from the early
1970s to 1991-93 is small, but localized increases in NO₃-N were observed in Coghian
Creek at the confluence with the Salmon River and in Davidson Creek.
Seven percent of the over 400 wells within the Salmon River watershed that have
been tested during the past 20 years have NO₃-N concentrations above the Canadian drinking water guideline of 10 mg L⁻¹. A spatial lag occurs between the location of wells
with elevated NO₃-N and the increase in NO₃-N in the surface water of the Salmon River
mainstem. This is attributed to the northward flow of ground water from the Hopington
Aquifer into the Salmon River.
Residential land use, (1600 septic systems installed since 1970) and agricultural landuse
were characterized by: i) a density index, an estimate of the land-use activity
immediately upstream of the water sampling station, and ii) a cumulative density index, the
density of the land-use activity in the entire watershed upstream of the water sampling
station. High density indices of both agricultural and residential activities are present in the
areas of high NO₃-N in surface and ground water, which suggests that both of these land-use
types are sources of NO₃-N. The pattern of the cumulative density index matches the
pattern ofNO₃-N in surface water more closely than the density index, and illustrates that
the water quality at a point in the river can reflect the land-use activities of the entire
watershed upstream. A spatial lag is observed between the higher density of land use
activities and the increase in NO₃-N in surface water.
Examining relationships between land use and water quality in the Salmon River
watershed is complicated by multiple sources ofNO₃-N in close proximity, changes in the
relative importance of sources within different locations in the watershed, and the temporal
and spatial lags between NO₃-N leaching from the land surface and its detection in the
ground and surface water. Using Spearman rank correlation, both agricultural activities and
septic systems are correlated to NO₃-N contamination of ground water. However, the
approach used in this study does not allow for the determination of the relative importance
of these two sources.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/5464 |
| Date | 11 1900 |
| Creators | Cook, Kathryn Emily |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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