Fresh water quality refers to the chemical, biological and physical characteristics in rivers, streams, creeks, lakes and other water bodies. These can be affected by natural processes as well as by people, and they may change considerably over the seasons, or over even shorter periods of time.

Some of the commonly measured chemical characteristics of water include:
  • Nutrients (e.g. nitrates and phosphates), which are required for plant growth but in excess can cause algae blooms that rob the water of oxygen
  • Dissolved oxygen, which is important for aquatic organisms such as fish and invertebrates
  • pH, a measurement of whether the water is acidic or basic, and determines what organisms can survive
  • Pollutants such as metals, pesticides and PCBs, that can enter the water and be taken up by plants and animals through a variety of pathways, often resulting in poor health or death (see also Pollution)
In terms of biological characteristics, the presence and levels of certain types of organisms such as invertebrates, bacteria, algae, viruses and protozoa, are monitored for ecosystem and human health. Physical characteristics include the temperature, relative density, turbidity and the amount of suspended solids in the water. All of these factors can affect the health of aquatic and riparian plants and animals, as well as those animals (including humans) that drink from fresh water sources.

Fresh water flows are the characteristics of moving water: the velocity, discharge, levels (high or low flows) and the variation of these characteristics over time. All streams and rivers have evolved to achieve a balance within their landscape. When their physical nature is altered, for example by channelization or damming, the energy of the flowing water is changed, and this can have profound effects on water quality as well as on the surrounding land area and ecosystems.

Fresh water quality and flow in the Capital Region

Here in the Capital Region, we are fortunate in having a reliable and safe source of drinking water. The drinking water for most of the region comes from the Sooke Lake Reservoir, and much of the watershed surrounding this reservoir is protected.

However, many of our local streams, lakes and wetlands are subject to water pollution and altered flows, which can affect the health of aquatic and riparian ecosystems and result in shellfish harvesting bans. These problems arise from a few main sources:
  • Chemicals such as oils, gasoline and heavy metals are washed into storm drains, and subsequently into streams and the ocean, from impervious surfaces such as roads, parking lots and driveways.
  • Runoff from urban areas with a high percentage of impervious surfaces also disrupts water flows, by causing sudden “flash” floods that can damage stream channels and cause erosion.
  • Pesticides and fertilizers are washed off agricultural fields, lawns and gardens and flow into streams and the ocean.
  • Some people still dispose of hazardous and toxic substances in storm drains (which feed into streams and marine bays and harbours) or in household drains (which are connected to the sewage lines that discharge into the Juan de Fuca Strait).
  • Sewage may enter streams, lakes and marine areas through improperly functioning septic systems and by “cross-connections” between sewage lines and storm drains (this latter problem is gradually being reduced as lines are upgraded and replaced).

Effects of Degraded Fresh Water Quality & Flows on Ecosystems

Chemical pollution

Chemical pollution can result in degraded water quality in a number of different ways, depending on the substance in question. Some chemicals are easily dissolved in water and can be absorbed directly through the tissues of aquatic plants and animals. For example, when fish respire, they draw water across their highly sensitive gill tissues, creating an entry pathway for toxic chemicals. Other substances tend to sink to the bottom of fresh and marine water bodies, where they become bound to sediments and may persist for years or even centuries before breaking down. Here they may be ingested by bottom-dwelling animals such as invertebrate larvae and crabs. Some of these persistent chemicals undergo biomagnification, which causes them to become more concentrated (and toxic) as they move up the food chain from small animals to larger predators. (See Pollution for more details about specific chemicals and how they affect plants and animals.)

Nutrient pollution

Nutrient pollution can be caused by excess nitrates and phosphates from sources such as sewage, detergents, fertilizers and livestock manure. This can lead to explosive algae growth; as bacteria break down the algae, they use up oxygen in the water, “robbing” it from fish and other aquatic organisms. During algae blooms, light penetration of the water is also reduced, preventing aquatic and marine plants from obtaining enough light to survive.


The amount of sediment in water bodies has important consequences for ecosystems. Too much sediment may be caused by erosion of the land in the surrounding watershed (e.g. due to activities such as construction and logging), or destruction of stream channels due to unnatural water flows in urbanized areas. Excess sediment can decrease the amount of light that penetrates the water, to the detriment of aquatic plants. It can also clog the gills of fish, and irritate their skin and eyes. When the sediment is deposited, it may bury salmon spawning beds, eelgrass meadows and other bottom habitats of fresh and marine water bodies. On the other hand, dams may block natural sediment transport, which is important for replenishing floodplains, deltas, mud flats and estuaries, all of which are important and productive ecosystems. Both excess and insufficient sediment supply can therefore create problems.

Water temperature

The water temperature is another important factor for maintaining the health of aquatic ecosystems. Warmer water contains less oxygen than cool water, since more dissolved oxygen molecules tend to escape (evaporate) from the liquid at higher temperatures. Some fish, notably salmonids such as Pacific Salmon and Cutthroat Trout, as well as their prey, require cool water and are particularly sensitive to changes in water temperature. Trees and shrubs growing on the banks of streams, lakes and wetlands shade the water and keep it cool (they also protect the banks from erosion and provide hiding places for fish). When this vegetation is removed, the resulting rise in water temperature can be quite dramatic. Many types of fish cannot survive in the altered conditions, while algae growth (and oxygen depletion) increases.


Fresh water flows are naturally variable, depending on the local climate, the characteristics of the watershed and the changes that occur during different seasons. The timing, magnitude and frequency of the changes in flow are also important. For example, high flows help to replenish floodplains with sediment, shape stream channels, flush away wastes and provide a spawning signal for fish. Low flows trigger insect breeding, provide sheltered pools for juvenile fish to grow and allow vegetation to colonize the floodplain. Water flows are disrupted by human-made infrastructure including impervious surfaces, dams, retaining walls, dykes and levees. Clearing the land of forest and natural vegetation, for the purposes of logging, construction and agriculture, also alters water flows (Related Information)

Effects of Degraded Fresh Water Quality & Flows on People

Many of the ecosystem effects of altered water quality and flows also affect people. As aquatic ecosystems are degraded, they are less able to provide many of the ecosystem services we rely on. For example, healthy riparian vegetation helps to filter and purify water that flows off the land, before it enters water bodies; it also soaks up excess water and prevents flooding.

Altered water flows can lead to property damage due to erosion, flooding and sediment deposition. Fish habitat can also be destroyed. Many salmon stocks in British Columbia are currently endangered, due in large part to the loss and degradation of spawning habitat. The Pacific Salmon is important as a keystone species, a prized food source, a commercially important industry, and a utilitarian as well as spiritual element of First Nations culture.

Drinking water quality is of course a major concern for human health. According to the United Nations, over one billion people on Earth do not have access to safe drinking water. Some types of bacteria, viruses and protozoa may cause illness or death, while algae and sediment can reduce the effectiveness of water purification treatments and place a strain on filtering devices. Most treatment systems effectively remove or inactivate microorganisms; however, there are chemicals that many systems do not remove, including pesticides, hydrocarbons, some metals and pharmaceutical drugs. In this area, we are fortunate enough to have a clean source of drinking water, as well as an effective treatment system.

Improving Fresh Water Quality & Flows

goldstream_waterfall 166x268  tallWays to Reduce Your Impact

  • Never dispose of hazardous household wastes down the drain or in storm drains. The CRD Recycling Guide contains information on disposal locations for items such as paint, used motor oil, pesticides and cleaners.
  • Reduce or eliminate the use of pesticides and fertilizers in your garden and on your lawn. Learn more about natural alternatives for pest control, composting techniques and native plants (which require less maintenance and chemical supplements). City Green
  • Wash your car over the lawn or a gravel area to prevent detergents from flowing directly into storm drains, which discharge into local streams and the ocean.
  • Help to reduce impervious surfaces around your home and in your neighbourhood by using pervious alternatives to asphalt and pavement, constructing narrower streets, driveways and paths, and installing native plant gardens in place of a standard lawn. Green Stormwater Infrastructure
  • When you undertake a construction project on your property, ensure that soil and sediment is not tracked onto the roads by vehicles, or otherwise washed into storm drains.
  • Use a broom instead of a pressure washer to clean your driveway and walkways; dirt and sediment washed into storm drains ends up in streams, where it can degrade water quality and damage fish habitat.
  • Encourage local businesses, developers, institutions and governments to adopt "best management practices" that protect water quality and flows.
  • Encourage the protection of natural streams and wetlands, which store water during times of high flow, and filter contaminants washed off the land.
  • Make sure your septic system is regularly inspected and maintained (see the CRD Septic Savvy Kit), to prevent water pollution with microorganisms and excess nutrients.
  • If you have a stream on your property, protect or restore the natural vegetation along the banks. This helps to prevent erosion, filters contaminants and provides wildlife habitat. Resist the urge to "tidy up" the stream by removing large woody debris, such as fallen trees, unless it poses a definite safety hazard in some way; this material helps to dissipate the energy of the water, prevents erosion, and provides sheltered areas for fish.
  • If you own livestock and have a stream on your property, consider installing a fence along stream banks to prevent the animals from causing erosion and pollution. Make sure manure is stored under cover, to prevent pollution of surface or groundwater with microorganisms and excess nutrients. Sustainable Agriculture
  • Get involved with a local stewardship group that conducts stream restoration and monitoring activities in your area.

Related Information

Emergency Contacts

Emergency Management of BC 1.800.663.3456
Report a Spill

Quick Links