Non-Point Source Pollution in BC
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British Columbia's environmental agencies, like in most other
jurisdictions, have focused primarily on controlling point sources
of water pollution, but we are now beginning to understand the
extent of NPS water pollution and the risk of not controlling
it. Many costs and problems are associated with NPS pollution,
drinking water and potential human risks;
to aquatic ecosystems, including fish, other aquatic organisms,
and their habitat;
losses to commercial and recreational fishing and shellfish
harvesting and impacts on traditional First Nations food harvesting
water-based recreation and tourism opportunities;
aesthetic of lakes, streams and coastal areas;
of remediation (e.g. payments for monitoring, clean-ups and
pollution reduction); and
real estate values.
source pollutants in aquatic ecosystems can be grouped into five
These microorganisms-bacteria, viruses, and protozoa-can cause
waterborne illnesses. While most pathogens come from human sewage
(primarily leaking or aging sewage collection systems, onsite
sewage systems, stormwater runoff, and combined sewer overflows),
manure from livestock and wild animal droppings are also common
Oxygen Depleting Substances
When organic wastes (e.g., manure, sewage, pulp and paper mill
effluent) decay in water, bacteria oxidize the waste, using up
oxygen dissolved in the water. If the oxygen is consumed beyond
a safe threshold, fish are stressed and will die when lethal levels
are reached. Anaerobic decomposition (without oxygen) produces
gases, such as hydrogen sulphide, that are lethal to many organisms.
Organic wastes and fertilizers can introduce plant-feeding
nutrients, such as nitrogen and phosphorus, into runoff. When
polluted runoff enters a waterbody, nutrients can cause algal
blooms and dense weed growth that disrupt the balance of aquatic
ecosystems and interfere with recreation such as swimming
and boating. When an algal bloom occurs, oxygen in the water
is depleted, which can cause odour and taste problems as well
as kill fish and other organisms. Certain kinds of algae may
be toxic to people and livestock.
soil particles make water turbid and unpleasant to drink,
and can reduce the effectiveness of drinking water treatment.
Sediments also reduce light available to algae and aquatic
plants, kill or injure fish by damaging their gills, cover
spawning gravel and smother fish eggs, and reduce the quality
of recreational activities such as swimming and boating.
Substances such as ammonia, nitrate, metals, pesticides
and a variety of organic toxins can poison humans, livestock,
wildlife, and aquatic organisms. Some toxins cause cancer.
Columbia, NPS water pollutants have produced a range of impacts.
In the enclosed marine waters of the Capital Regional District
(CRD), NPS water pollution has adversely affected recreational
opportunities, degraded aesthetic values, and reduced the abundance
and diversity of marine life. Victoria and Esquimalt harbours
remain closed to commercial crab harvesting due to dioxin/furan
contamination. Beach closures have been common throughout the
CRD, primarily due to fecal matter discharged into stormwater
systems. Although recent identification and elimination of sources
of pathogens in storm drains that discharge near beaches has allowed
beaches to reopen, several dozen storm drains remain a significant
concern. In Saanich Inlet, most embayed areas are closed to shellfish
harvesting due to fecal contamination associated with agricultural
runoff, onsite sewage systems, and stormwater runoff. High levels
of heavy metals have been measured in sediments near stormwater
outfalls. These contaminants can cause sublethal toxicity to bottom-dwelling
In areas of the Lower Fraser Valley, east from Vancouver, the
most significant potential for NPS water pollution is the agriculture
industry. The Abbotsford-Sumas aquifer is contaminated with nitrate
leached from manure and other fertilizers applied to crops and
fallow fields. Nitrate contamination is also evident in other
aquifers, including Hopington and Brookswood, due to agricultural
activities and onsite sewage disposal.
the eastern Fraser Valley and in less urbanized areas of Langley
and Surrey exhibit depressed oxygen levels caused by agricultural
runoff. Low oxygen levels have contributed to coho salmon kills
in the Nicomekl, Serpentine, and Little Campbell Rivers near Boundary
Bay in the 1980's. The same conditions exist in Matsqui Slough.
In the more
urbanized areas of the Lower Mainland, the negative impacts of
stormwater runoff, combined sewer overflows, and occasional toxic
spills have been significant. Fish kills have occurred. Nutrients
and fecal contamination have reduced aesthetic values and recreational
use of urban lakes. Stormwaters and combined sewer overflows contribute
a significant contaminant load to Burrard Inlet, where toxic metals
and organic chemicals in the sediments are potentially toxic to
sewage treatment to control point-source phosphorus loading to
the Okanagan Lakes over the past 25 years has led to significant
improvements in water quality in most lakes. However, phosphorus
inputs from non-point sources in this area remain a concern, and
account for over 90% of total phosphorus loadings in the Okanagan
In the Armstrong,
Osoyoos, and Grand Forks areas, ground water has been contaminated
with nitrates from chemical fertilizers leaching from orchards
and other crops. Corrective action should reduce the problem,
but unless other NPS pollution from agriculture, forestry and
stormwater are also controlled, deteriorating ground water quality
from increasing nitrate levels could continue.
In the cattle
ranching areas of the Northern and Southern Interior, water pollution
from agriculture is widespread. Phosphorus loadings in runoff
from cattle over-wintering areas have contributed to the eutrophication
of Williams Lake in the Cariboo, with blooms of blue-green algae
and critical oxygen depletion in lake bottom waters. Agricultural
runoff has also affected the Thompson River and its tributaries-the
Bonaparte, Nicola, and Salmon rivers. Where cattle have direct
access to streams, bank erosion leads to vegetation loss, bank
destabilization, and damaging sedimentation. Cattle manure can
contaminate drinking water and harm fish by depleting dissolved
areas, localized discharges from boats and marinas, storm drains,
onsite sewage systems, and agricultural runoff affect enclosed,
poorly-flushed bays, forcing shellfish harvesting closures to
prevent health risks.
areas of British Columbia, NPS pollution tends to be localized
rather than widespread, generally associated with land development
and population growth. Land development not only increases NPS
pollution directly through erosion and sedimentation from land
clearing and excavation, but also increases the opportunities
for NPS pollution from other sources.
effects of non-point source water pollutants, along with regulated
point sources, may exceed the carrying capacity of surface and
ground waters. Understanding the connection between land use, the
degree of development, and water quality is important. This allows
us to target sensitive areas and apply preventative solutions
such as changing public behavior, applying alternate business
practices or investing in innovative technologies.
Causes of Non-Point Source Water Pollution in British Columbia
contaminants in water, the greater the risk to humans, fish, and
animals. Even small amounts of contaminants in small amounts of
runoff result in cumulative effects over an entire watershed and,
building up over time, can have a significant impact. Locating
the sources of pollution and removing contaminants before they
reach the water provides the best assurance of clean water in
The main potential causes of non-point source water pollution
in British Columbia are:
Development: has its greatest effect in the major urban
regions — the Lower Mainland, east coast of Vancouver
Island, and the Okanagan Valley.
can affect water quality in the Lower Fraser Valley, Cariboo,
Thompson, and Okanagan basins, and the east coast of Vancouver
Runoff: stormwater runoff often contaminates receiving waters
in all urban areas of the province, but is of greatest concern
in the Greater Vancouver and Capital Regional Districts.
Sewage Systems: poorly maintained and poorly located on-site
systems primarily affect populated inland lakes, enclosed marine
bays, and vulnerable aquifers.
can affect fish, fish habitat and drinking water throughout
the province when it causes an increase in sedimentation.
Deposition: includes dustfall, acidic rainfall, and air
emissions. Water quality effects are primarily felt down-wind
from urban areas, but long-range transport of persistent organic
pollutants can occur.
and Marine Activities: primarily affects waters around major
commercial ports, boat yards, and poorly-flushed marine and
Non-Point Source Water Pollution in British Columbia: An Action
Plan. 1999. Ministry of Environment, Lands and Parks (now
called Ministry of Water, Land and Air Protection).