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Water – How good is it?


What do we mean by water quality?

Water quality is defined in terms of the chemical, physical, and biological content of water. The water quality of rivers and lakes changes with the seasons and geographic areas, even when there is no pollution present. There is no single measure that constitutes good water quality. For instance, water suitable for drinking can be used for irrigation, but water used for irrigation may not meet drinking water guidelines. Canadian water quality guidelines provide basic scientific information about water quality parameters and ecologically relevant toxicological threshold values to protect specific water uses.

For information on drinking water guidelines and recreational water quality, visit Health Canada's Web site. 

For information on the Canadian water quality guidelines for the protection of aquatic life and for agricultural water uses (irrigation and livestock water), contact:

National Guidelines and Standards Office
Environment Canada
Ottawa, ON  K1A 0H3
Tel.: 819-953-1550
Fax: 819-953-0461
E-mail: ceqg-rcqe@ec.gc.ca
Web site: Canadian Water Quality Guidelines 


What are the key factors that influence water quality?

Many factors affect water quality. Substances present in the air affect rainfall. Dust, volcanic gases, and natural gases in the air, such as carbon dioxide, oxygen, and nitrogen, are all dissolved or entrapped in rain. When other substances such as sulphur dioxide, toxic chemicals, or lead are in the air, they are also collected in the rain as it falls to the ground.

Rain reaches the earth's surface and, as runoff, flows over and through the soil and rocks, dissolving and picking up other substances. For instance, if the soils contain high amounts of soluble substances, such as limestone, the runoff will have high concentrations of calcium carbonate. Where the water flows over rocks high in metals, such as ore bodies, it will dissolve those metals. In the Canadian Shield, there are large areas with little soil and few soluble minerals. Consequently, the rivers and lakes in these areas have very low concentrations of dissolved substances.

Another factor influencing water quality is the runoff from urban areas. It will collect debris littering the streets and take it to the receiving stream or water body. Urban runoff worsens the water quality in rivers and lakes by increasing the concentrations of such substances as nutrients (phosphorus and nitrogen), sediments, animal wastes (fecal coliform and pathogens), petroleum products, and road salts.

Industrial, farming, mining, and forestry activities also significantly affect the quality of Canadian rivers, lakes, and groundwater. For example, farming can increase the concentration of nutrients, pesticides, and suspended sediments. Industrial activities can increase concentrations of metals and toxic chemicals, add suspended sediment, increase temperature, and lower dissolved oxygen in the water. Each of these effects can have a negative impact on the aquatic ecosystem and/or make water unsuitable for established or potential uses.


How do we measure water quality?

The quality of water is determined by making measurements in the field or by taking samples of water, suspended materials, bottom sediment, or biota and sending them to a laboratory for physical, chemical, and microbiological analyses. For example, acidity (pH), colour, and turbidity (a measure of the suspended particles in the water) are measured in the field. The concentrations of metals, nutrients, pesticides, and other substances are measured in the laboratory.

Another way to obtain an indication of the quality of water is biological testing. This test determines, for example, whether the water or the sediment is toxic to life forms or if there has been a fluctuation in the numbers and kinds of plants and animals. Some of these biological tests are done in a laboratory, while others are carried out at the stream or lake.


How does water quality in Yukon compare with that in Northwest Territories?

The Yukon has much more variable water quality and generally higher levels of sediment than the Northwest Territories, except for the mountainous western part of the Mackenzie River basin. This is due in part to the more rugged terrain in the Yukon, which has several large mountain ranges (such as the St. Elias on the west and the Mackenzie Mountains on the east). Much of the rest of the Northwest Territories is dominated by Canadian Shield terrain, which is much older, has less relief, and is largely scraped bare of readily erodible material by continental glaciation. The extreme seasons in the Yukon, combined with its complex geology, glaciation, and sources of erodible material, are also a contributing factor.


What is good quality drinking water?

Good quality drinking water is free from disease-causing organisms, harmful chemical substances, and radioactive matter. It tastes good, is aesthetically appealing, and is free from objectionable colour or odour. The guidelines for Canadian drinking water quality specify limits for substances and describe conditions that affect drinking water quality.

For a copy of Guidelines for Canadian Drinking Water Quality, visit Health Canada's Web site. 


How can we be sure that water is safe to drink?

Municipalities have the responsibility to provide their citizens with safe drinking water and to provide sufficient warning about pollution risks related to recreational uses. Samples are regularly collected and analyzed to check drinking water quality. The results of these analyses are compared with the Canadian drinking water quality guidelines to decide whether or not the water is safe to drink.

It should be noted that there is a difference between "pure water" and "safe drinking water".

Pure water, often defined as water containing no minerals or chemicals, does not exist naturally in the environment. Under ideal conditions, water may be distilled to produce "pure" water.

Safe drinking water, on the other hand, may retain naturally occurring minerals and chemicals, such as calcium, potassium, sodium, or fluoride, which are actually beneficial to human health and may also improve the taste of the water. Where the minerals or chemicals occur naturally in concentrations that may be harmful or displeasing, then certain water treatment processes are used to reduce or remove the substances. In fact, some chemicals are actually added to produce good drinking water; the best examples of chemical addition are chlorine, used as a disinfectant to destroy microbial contaminants, and fluoride, used to reduce dental cavities.


Some of my friends buy bottled water for drinking and cooking. What is my assurance that bottled water is good quality drinking water?

Sales of bottled water continue to increase each year. The Canadian Bottled Water Association reports that 1998 consumption was estimated at 703 million litres. Recently, the bottled water industry provided Canadians with potable drinking water during times of crises -- the floods in Quebec and Manitoba and the ice storm in Ontario and Quebec.

Bottled water is regulated as a food product under the Food and Drugs Act. Federal food inspectors regularly audit the operations of bottled water companies to ensure compliance. Members of the Canadian Bottled Water Association (CBWA) produce about 85% of the bottled water in Canada. Since 1990, these members are subject, not only to federal and provincial regulations, but also to third-party inspections, water testing and analysis, and adherence to the CBWA Model Code. For additional information on the standards required of CBWA members, contact:

Canadian Bottled Water Association 
70 East Beaver Creek Road, Suite 203-18
Richmond Hill, Ontario  L4B 3B2
Tel.: 905-886-6928
Fax: 905-886-9531
E-mail: info@cbwa-bottledwater.org


Are drinking water supplies in urban areas better or worse than those in rural areas?

The answer to this is not a simple "yes" or "no". In general, one can say that the quality of water in rural areas is better because these areas are removed from industrial activities, which may result in the degradation of the quality of river water, lake water, or groundwater. There are, however, many exceptions. In areas with intensive agricultural activity, mining, and logging, the impacts on water quality can be severe.


If we could boil all the water we consume, could we eliminate pollution?

No. Boiling water kills germs but will not remove heavy metals and chemicals.


Is chlorine in the water supply necessary, and could it become a health hazard?

Chlorine was introduced as a disinfectant in water treatment around 1900. It has since become the predominant method for water disinfection. Apart from its effectiveness as a germicide, it offers other benefits such as colour removal, taste and odour control, suppression of algal growths, and precipitation of iron and manganese. In addition, chlorine is easy to apply, measure, and control. It is quite effective and relatively inexpensive.

Chlorine as a disinfectant in water treatment can be a health hazard if its concentration or the concentrations of certain by-products (e.g., trihalomethanes, a chlorinated organic compound) are greater than the Canadian drinking water quality guidelines allow. If the maximum acceptable concentrations are exceeded, the authorities responsible for public health should be consulted for the appropriate corrective action.


Some people say that you shouldn't pour solvents and other household chemicals down the drain because they pollute the rivers and lakes. Is that true? How else can I get rid of them?

While household chemical products are generally safe for the uses they are designed for, some may become harmful to the environment as they accumulate in it. For this reason you should not put these products down a drain. Most sewage treatment facilities are not capable of removing such toxic substances. You should also be aware, in most instances, that anything put into the storm sewer system goes directly to the receiving lake or river completely untreated. So, before you dump anything down a drain or into a storm sewer, remember that you or others may be drinking it some day.

For those substances that you have at home now and want to get rid of, such as old paint, find out whether there is a hazardous waste disposal site in your community and take them there. You may also contact your local environmental health officer for assistance. Make sure the containers are labeled to indicate the contents.


As a responsible consumer how can I tell if the products I buy are potentially harmful to the environment?

Most household chemical products and pesticides sold in Canada have warning labels. These labels tell us whether the product is flammable, poisonous, corrosive, or explosive. The labels usually also give first aid instructions.

Keep in mind that some products that are hazardous do not require warning labels. Canadian laws for hazardous household chemicals are regulated by Health Canada. The laws for pesticides (such as mothballs, house and garden pesticides, or insect repellents) are controlled by Agriculture and Agri-Food Canada. The symbols used on hazardous household chemical products are shown below:

Symbols used on hazardous household chemical products.

Details can be found below

Symbols used on hazardous household chemical products

The warning symbols are based on shape: the more corners a symbol has, the greater the risk. When shopping for household chemical products, always look for these symbols. Read the label to find out how to use the product safely and what precautions to take for its disposal.

For more information on product safety, visit Health Canada's Web. 


What happens to water that drains out of our home?

Sewers collect the liquid waste and discharge it into lakes, streams, or the ocean. Most, but not all, municipalities treat their sewage using mechanical and/or biological processes before discharging it. Regardless of the process, sewage treatment plants concentrate the sewage into a solid called "sludge", which is then used on agricultural land, disposed of in a landfill site, or incinerated. Residents of rural areas, the North, and cottage country may have individual septic systems or have sewage collected by truck. Waste from outdoor privies slowly percolates through the ground along with other groundwater. It can end up infecting lakes, streams, or wells if located too close to these sources of water.


How effective are wastewater treatment plants in eliminating water pollution?

Conventional wastewater treatment plants remove suspended solids and some of the organic matter. More advanced plants also remove phosphorus and nitrogen, which are nutrients for aquatic plants. Both of these nutrients are present in human sewage as well as in runoff from agricultural areas. Laundry detergents were once a major source of phosphorus, but regulations controlling its use in detergent manufacturing have minimized its impact on receiving waters in Canada.


Who determines whether or not a beach should be closed?

Regional health officers determine whether or not a beach should be closed using the guidelines for Canadian recreational water quality developed jointly by federal and provincial experts. These guidelines deal mainly with health hazards in instances where people have direct recreational contact with water. This includes infections transmitted by pathogenic microorganisms, such as microbes and viruses, and injuries due to impaired visibility in muddy waters. When a public beach is unsafe for swimming, warning posters are displayed in visible locations.

For a copy of Guidelines for Canadian Recreational Water Quality, visit Health Canada's Web site. 


Eutrophication is a form of pollution. What is a eutrophic lake?

Eutrophication is the natural aging process of lakes as they become better nourished, either naturally or artificially. Eutrophication occurs naturally with the gradual input of nutrients and sediment through erosion and precipitation, resulting in a gradual aging of the lake. Humans speed up this natural process by releasing nutrients, particularly phosphorus, into rivers and lakes through municipal and industrial effluent and through increased soil erosion resulting from poor land use practices. Eventually, a lake will develop high nutrient concentrations and dense growths of aquatic weeds and algae. These plants die and decompose, causing depletion of dissolved oxygen in the water. This process often results in fish kills and changes in a lake's fish species. Ultimately, eutrophication will fill the lake with sediment and plant material.


How does irrigation affect water quality?

Irrigation affects water quality in different ways, depending on the original water quality, the type of soil, the underlying geology, the type of irrigation, the crop grown, and the farming methods used.

Although a large portion of irrigation water is used by plants (evapotranspiration) or evaporates from the soil, part of it is returned to the source. As is often the case with water use, when the water returns to the stream or water body, the quality has been lowered. The water that runs off the fields carries with it sediments, fertilizers, herbicides, pesticides (if these chemicals are used on the fields), and natural salts leached from the soil, and eventually these substances enter our rivers, lakes, and groundwater supplies.


Is the discharge of cooling water from electrical power plants a form of pollution?

Yes; it is called "thermal pollution". In 1996 -- the last year for which national estimates are available -- thermal and nuclear power plants in Canada discharged 28 billion cubic metres of water. Almost all of this had been used for condenser cooling. However, most of these facilities have controls on the maximum temperature of their discharge waters, and many of them use cooling ponds or towers.

Thermal pollution, when not regulated, can be a problem. Artificially heated water can promote algae blooms, threatening certain species of fish and otherwise disturbing the chemistry of the receiving water body. When this water is not reused by industries or for heating in nearby communities, large amounts of energy and potential dollar savings are lost. When it is reused, it can also have an improved effect on climate change by displacing the use of some fossil fuels.


What effect can a dam have on the water quality of a river system?

Generally, rivers are dammed to create reservoirs for power production, downstream flood control, recreation, or irrigation. When a dam is constructed, the land behind it is flooded. This may mean the loss of valuable wildlife habitat, farmland, forests, or town sites. Accumulation of sediments in the reservoir can have a detrimental effect on water quality by creating increased concentrations of harmful metal and organic compounds in the reservoir. If vegetation is not removed behind the dam before flooding, other problems can occur. For example, the eutrophication process may occur at a faster rate and adversely affect the water quality.


What is dredging?

Dredging is the removal of sediments or earth from the bottom of water bodies using either a type of scoop or a suction apparatus. This material, often called "spoils", is then deposited along the shore, formed into islands, or transported elsewhere away from the site. Dredging is usually done to increase the depth or width of water channels for navigation or to allow increased flow rates to accommodate larger volumes of water.


Can dredging do any harm?

Dredging can disturb the natural ecological balance through the direct removal of aquatic life. For example, in estuaries (part of the river mouth where fresh water and seawater are mixed), oyster beds can be destroyed; in the freshwater environment, those bottom-dwelling organisms on which fish depend for food may be eliminated from the food chain. In addition, when spoils are deposited directly in a water system, they may smother the remaining organisms, and silt or sediments released from dredging activities can cover and destroy fish feeding and breeding habitats.

Furthermore, contaminants accumulate over long periods of time in the sediments. Some toxic substances which may reside in the sediment (e.g., mercury) can re-enter the water system when the sediments are dredged. Such contaminants then endanger the health of water users, particularly the organisms that live in the body of water. Nutrients are also released by dredging. These can cause eutrophication of the system, resulting in oxygen depletion and possibly the death of fish and other aquatic organisms.


Can dredging be beneficial to the aquatic ecosystem?

Yes, in some instances, dredging is beneficial to the environment. Dredging can be used to enlarge or create wetlands and provide more habitat opportunities and greater biological diversity within targeted geographic area. In some cases, disturbed lake and river bottoms can be re-colonized once the actual dredging activities have stopped. Dredged spoils can be used to create islands and contoured shorelines which can provide nursery habitat for fish, nesting and staging habitat for waterfowl, and winter habitat for furbearing mammals. In many cases, however, the material removed by dredging (i.e., dredgeate) requires containment or treatment and would not be suitable for wildlife habitat creation.

Although dredging can disturb the normal balance and productivity of an aquatic ecosystem, proper attention to mitigation and construction procedures may result in the beneficial effects of dredging outweighing the negative effects.


What is acid rain?

Acid rain refers to rainwater that, having been contaminated with chemicals introduced into the atmosphere through industrial and automobile emissions, has had its acidity increased beyond that of clean rainwater. Acidity is measured on a pH scale. For example, vinegar, an acid, has a pH of 3, and lemon juice, another acid, has a pH of 2. It is generally accepted that rain with a pH less than 5.3 is acidic. 

The pH scale

Details can be found below

The pH scale. The illustration of the pH scale is marked to show the alkalinity or acidity of a number of different substances, as follows: lye: pH 13 ammonia: pH 12 milk of magnesia: pH 10.5 baking soda, sea water: pH 8.5 milk: pH 6.5 vinegar: pH 3 lemon juice: pH 2 battery acid: pH 1 The illustration also shows that the normal range of stream pH is 6 to 8; the normal range of precipitation pH is 5 to 6.5; fish reproduction is affected at pH 4 to 5; adult fish die at pH 3 to 4; and the pH range of acid rain is 1 to 5.

Emissions of sulphur and nitrogen oxides from a variety of sources enter the atmosphere everyday. While in the atmosphere, these compounds combine with atmospheric water to form acids. The most common acids formed in this manner are sulphuric acid and nitric acid. When mixed with rain, these acids fall as wet deposition (acid rain). In the absence of rain, the particulate matter slowly settles to the ground as dry deposition. Together, wet and dry deposition of acidic substances is known as acid precipitation.


How does acid deposition affect water quality?

The effects of acid deposition on water quality, although complicated and variable, have been well documented. Impacts from these acidic compounds in the atmosphere can occur directly, by deposition on the water surface, or indirectly, by contact with one or more components of the terrestrial ecosystem before reaching any aquatic system. The interactions of acid deposition with the terrestrial ecosystem, including vegetation, soil, and bedrock, result in chemical alterations of the waters draining these watersheds, eventually altering conditions in the lakes downstream.

The extent of chemical alteration resulting from acidic deposition depends largely on the type and quantity of the soils and the nature of the bedrock material in the watershed, as well as on the amount and duration of the precipitation. Watersheds with soils and bedrock containing substantial quantities of carbonate-containing materials, such as limestone and calcite, are less affected by acidic deposition because of the high acid-neutralizing capacity derived from the dissolution of this carbonate material. Thousands of lakes in Canada, however, lie on the Precambrian Shield. This vast expanse of bedrock possesses few limestone-type materials and, consequently, has only a limited ability to neutralize acidic deposition. Consequently, lakes and rivers in these areas generally show acidification effects, including decreasing pH levels and increasing concentrations of sulphate and certain metals such as aluminum and manganese.


What is acid mine drainage?

Acid mine drainage or, more generally, acid rock drainage, results when rock containing metallic sulphides, such as pyrite, become exposed to water and air. Examples of this are mine tailings and excavation of acid rock through highway construction. The rate of acid generation is greatly enhanced by the presence of sulphur-oxidizing bacteria.

The impact of this process is increased acidity and metal levels in receiving waters (surface water and groundwater) to the detriment of fish and other organisms, as well as to drinking water supplies.


Our northern rivers and lakes have long been considered to be of pristine quality. Is this still true?

The quality of Canada's northern rivers and lakes is generally good in comparison with the extensively utilized watercourses in the heavily populated regions of southern Canada.

Some pollution concerns do exist in the North, and these must be closely monitored to ensure that good water quality is conserved. The North contains significant reserves of gold, silver, uranium, other metals, and diamonds, which have led to the development of a number of mining operations throughout the North. By-products from the mines can include metals such as copper, lead, zinc, arsenic, and cyanide, which are discharged into receiving waters. A number of large uranium ore bodies have been discovered in the southern Keewatin part of Nunavut, but none have been developed yet, due to public concerns about the potential for negative environmental impacts.

The operation of oil and gas facilities in northern Alberta and in the Mackenzie valley, could lead to a degradation of water quality either through accidental spills in the refinery or along the transportation route. Monitoring of water, suspended sediments, and instream biota is required to ensure that water quality is not deteriorating.

Toxic organic compounds such as organochlorine pesticides and PCBs (polychlorinated biphenyls) have also been detected in snow and in fish in the Northwest Territories. The exact pathways for entry of these compounds into northern waters have not yet been identified, but they likely include long-range atmospheric transport from agricultural and industrial sources in the south or from other continents.

Long-term comprehensive monitoring for northern rivers and lakes is essential to keeping governments, the public, developers, and industrial users informed on the quality of northern rivers and lakes. This information is required by regulatory agencies to ensure that water quality concerns can be addressed before they become problems. The marine water system in the North, in contrast to the freshwater one, has had significant inputs of contaminants from various global sources, including long-range air and sea transport. The resultant contamination of water and especially of country (native) foods is of particular concern to the Inuit, many of whom live near the sea and depend on it for their food.

To learn more about research into contaminants in the North, visit the National Water Research Institute's Web site.


Has water quality in Canada improved or deteriorated in the last ten years?

In some aspects it has improved, while in others it has deteriorated. Some problems identified 10 or 20 years ago have been partly solved. However, we have also identified new problems. For example, although the problem of accelerated eutrophication has not disappeared as a threat to our aquatic ecosystems, we can say that this problem is now largely under control in the Great Lakes basin where regulations have proven effective. Although we must continue to take great care in limiting the discharge of phosphorus into our lakes and rivers, attention is now being directed more toward addressing issues associated with toxic chemicals.

Today, in terms of water quality, toxic chemicals overshadow all other problems in the Great Lakes and in many other water bodies in Canada. Although we are striving to solve this threat to water quality, we still have a long way to go before it is under control.


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