The Canadian Water Quality Index (CWQI) is an effective method to rate the water quality and determine its suitability for drinking purposes. CWQI measures a wide variety of parameters of water quality and then cumulatively translates them into one score.
The CWQI method requires a group of parameters that have drinking water objectives that have been set either by the Canadian government or a province to ensure that the water intended for human consumption.
Health-Related Standards: shall not contain disease-causing organisms or unsafe concentrations of toxic chemicals.
Aesthetic Objectives: should be aesthetically acceptable and palatable.
Operational Guidelines: should not contain undesirable concentrations of parameters that, if not controlled, may negatively affect the efficient and effective treatment, disinfection, and distribution of water
The CWQI calculates three factors based on these objectives:
A summary of results comes in two charts. First one shows CWQI and the second one shows which and how parameters influence CWQI.
The colouring system is represented by:
The sample example provided has a CWQI of 68 (out of 100). The quality is FAIR.
The My Water Quality Report Card also provides a detailed summary of the parameters tested, why each parameter is important, and treatment options. This information can be found in Appendix A of each report card.
Your untreated water contains Total Coliform bacteria.
Your water contained elevated concentrations of Lead.
Your CWQI result for health parameters in your raw, untreated, water is Marginal
Your untreated water contained elevated concentrations of Total Coliform.
Your CWQI result for health parameters in your raw, untreated, water is Poor
Your water contained elevated concentrations of True Colour, Total Hardness (as CaCO3), Total Dissolved Solids.
Your CWQI result for aesthetic and operational parameters in your raw, untreated, water is Fair
Your water contained elevated concentrations of True Colour, Sodium, Total Hardness (as CaCO3), Total Dissolved Solids.
Your CWQI result for aesthetic and operational parameters in your raw, untreated, water is Poor
Maximum Acceptable Concentration [MAC objective] is established for parameters which when present above a certain concentration, have known or suspected adverse health effects.
| Parameter | Unit | MAC Objective | Your Result (Treated) | Your Result (RAW) |
|---|---|---|---|---|
| Fluoride | mg/L | 1.5 | <0.05 | <0.05 |
| Nitrate (as N) | mg/L | 10 | 3.93 | 3.98 |
| Nitrite (as N) | mg/L | 1 | <0.05 | <0.05 |
| Escherichia coli | CFU/100mL | 0 | 0 | 0 |
| Total Coliform | CFU/100mL | 0 | 0 | 29 |
| Free Cyanide | mg/L | 0.2 | 0.001 | 0.002 |
| Aluminum | ug/L | 2.9 | 2 | 2 |
| Antimony | ug/L | 0.006 | <0.5 | <0.5 |
| Arsenic | ug/L | 0.01 | <1 | <1 |
| Barium | ug/L | 1 | <1 | 144 |
| Boron | ug/L | 5 | 23 | 24 |
| Cadmium | ug/L | 0.005 | <0.1 | <0.1 |
| Chromium | ug/L | 0.05 | 4 | 4 |
| Copper | mg/L | 2 | 26 | 13 |
| Lead | ug/L | 0.005 | 105 | 0.1 |
| Manganese | mg/L | 0.12 | <1 | <1 |
| Mercury | ug/L | 0.001 | <0.1 | <0.1 |
| Selenium | ug/L | 0.01 | <0.2 | 0.5 |
| Strontium | ug/L | 7 | <1 | 240 |
| Uranium | ug/L | 0.02 | <1 | <1 |
| Zinc | mg/L | 3 | 5 | 9 |
| Parameter | Description | Health Effects |
| Lead | Lead is a naturally occurring element. However, naturally occurring lead is rarely found dissolved in drinking water sources. The main source of lead in drinking water is through corrosion of plumbing materials with lead or brass components, such as in some pipes, solder, faucets, fittings, and older galvanized well liners. | Health basis of MAC: Reduced intelligence in children measured as decreases in IQ is the most sensitive and well established health effect of lead exposure. There is no known safe exposure level to lead. Other: Possible effects include behavioral effects in children. Reduced cognition, increased blood pressure, and renal dysfunction in adults are also possible. Classified as probably carcinogenic to humans |
Aesthetic Objective (AO) AOs are established for parameters that may impair the taste, odour or colour of water or which may interfere with good water quality control practices. For certain parameters, both aesthetic objectives and health-related MACs have been derived.
Operational Guidelines (OG) OGs are established for parameters that, if not controlled, may negatively affect the efficient and effective treatment, disinfection and distribution of the water.
| Parameter | Unit | AO/OG Objective | Your Result (Treated) | Your Result (RAW) |
|---|---|---|---|---|
| Chloride | mg/L | 250 | 161 | 163 |
| Sulphate | mg/L | 500 | 14.4 | 14.7 |
| True Colour | TCU | 5 | 5.1 | 6.9 |
| Dissolved Organic Carbon | mg/L | 5 | 2.7 | 2.9 |
| Copper | mg/L | 1 | 26 | 13 |
| Iron | mg/L | 0.3 | 33 | 100 |
| Manganese | mg/L | 0.02 | <1 | <1 |
| Sodium | mg/L | 200 | 239.0 | 75.4 |
| Zinc | mg/L | 5 | 5 | 9 |
| pH | pH | 6.5 - 8.5 | 7.61 | 7.48 |
| Total Hardness (as CaCO3) | mg/L | 80 - 100 | 0.9 | 334 |
| Total Dissolved Solids | mg/L | 500 | 640 | 750 |
| Parameter | Description | Treatment Options |
| True Colour | The aesthetic objective for colour in drinking water is 5 TCU (True Colour Units). Water can have a faint yellow/brown colour which is often caused by organic materials created by the decay of vegetation. Sometimes colour may be contributed to by iron and manganese compounds produced by processes occurring in natural sediments or in aquifers. The presence of organic materials is the main cause of disinfection by-products when water is treated with chlorine. | Water Softener |
| Sodium | Sodium is a common element in the natural environment and is often found in food and drinking water. In drinking water, sodium can occur naturally or be the result of road salt application, water treatment chemicals or ion-exchange water-softening units. At concentrations greater than 200 mg/L the water will have a strong salty taste. | Distillation, Reverse Osmosis |
| Total Hardness (as CaCO3) | The operational guideline for hardness in drinking water is set at between 80 and 100 mg/L as calcium carbonate. Hardness is caused by dissolved calcium and magnesium, and is expressed as the equivalent quantity of calcium carbonate. On heating, hard water has a tendency to form scale deposits and can form excessive scum with regular soaps. However, certain detergents are largely unaffected by hardness. Conversely, soft water may result in accelerated corrosion of water pipes. Hardness levels between 80 and 100 mg/L as calcium carbonate (CaCO3) are considered to provide an acceptable balance between corrosion and incrustation. Water supplies with a hardness greater than 200 mg/L are considered poor but tolerable. Hardness in excess of 500 mg/L in drinking water is unacceptable for most domestic purposes. | Water Softener, Distillation |
| Total Dissolved Solids | Naturally occurring; sewage, urban and agricultural runoff, industrial wastewater. TDS above a concentration of 500 mg/L can effect taste and result in excessive scaling in water pipes, water heaters, boilers and appliances. | Reverse Osmosis |
