Alberta river water quality index
- Rating System
- What Does the Index Show?
- How is the Index Used?
- Frequently Asked Questions
An index, whether it is for water quality, air quality or the stock market, is a mathematical way of combining a number of variables into one easily understood value. The Alberta River Water Quality Index was developed specifically as a way to summarize physical, chemical and biological data into a simple descriptor of water quality. The Index provides a simple snapshot of annual water quality conditions in major rivers of the province.
Alberta Environment monitors surface water quality at many river and lake locations each year, but only data collected as part of the province's Long-term River Network are currently used for the Index. Index values are calculated annually for each site based on data collected monthly or quarterly from April to March. Sites are chosen to represent water quality conditions up- and downstream of areas of significant human activity.
The Alberta River Water Quality Index is based on the average of four sub-indices calculated annually for four variable groups:
- Metals (up to 22 variables measured quarterly);
- Nutrients (6 variables measured monthly);
- Bacteria (2 variables measured monthly); and
- Pesticides (17 variables measured 4 times during open-water season).
Variables in the first three groups are compared to Alberta and federal water quality guidelines. Variables in the fourth group (pesticides) are evaluated based on if they can be detected in a water sample. This conservative approach was adopted because some pesticides do not yet have official guidelines and, unlike metals, nutrients and bacteria, pesticides do not occur naturally in the environment.
Following are the variables used in the River Water Quality Index:
|Metals & Ions|
|Nutrients & Related Variables|
|Dissolved Oxygen||Total Phosphorus||Nitrite-Nitrogen (NO2-N)|
|pH||Total Nitrogen||Ammonia Nitrogen|
|Fecal Coliforms||Escherichia coli|
To view objectives used in the Index calculation, click here.
The formula used to calculate the individual sub-indices is the same as that used for the Canadian Council of Ministers of the Environment Water Quality Index. However, the method for compiling the overall Index is tailored to Alberta.
The Index formula is based on three aspects of water quality that relate to water quality objectives:
- Scope (F1)- how many variables do not meet objectives?
- Frequency (F2)- how frequently do measurements not meet objectives?
- Amplitude (F3)- by how much do measurements not meet objectives?
Formulation PDF 67 Kb
Index results are reported as a number between 0 and 100, where 100 represents the best quality, relative to objectives. The numbers are further ranked into five categories:
96 - 100
|Excellent - Guidelines almost always met; best quality|
81 - 95
|Good - Guidelines occasionally exceeded, but usually by small amounts; threat to quality is minimal|
66 - 80
|Fair - Guidelines sometimes exceeded by moderate amounts; quality occasionally departs from desirable levels|
46 - 65
|Marginal - Guidelines often exceeded, sometimes by large amounts; quality is threatened, often departing from desirable levels|
0 - 45
|Poor - Guidelines almost always exceeded by large amounts; quality is impaired and well below desirable levels; worst quality|
Index values are calculated for the four variable groups (metals, nutrients, pesticides and bacteria). These are then averaged, as in the following example, to produce an overall River Water Quality Index:
Water quality varies naturally from site to site and from year to year. For example, water quality may appear better in drier years, since dry conditions cause less surface runoff and fewer contaminants coming from the land to the river. However, most persistent trends can be linked to human influence. Any activity that alters water quantity or affects inputs from point sources (e.g., sewage outfalls) or non-point sources (e.g., agricultural run-off) has the potential to influence water quality. Upgraded municipal wastewater treatment has improved water quality downstream of major cities, such as Lethbridge, Calgary, Red Deer and Edmonton; the Bacterial sub-Index reflects this improvement.
Index results are used to evaluate the general quality of river water with respect to four groups of variables: metals, nutrients, bacteria and pesticides. River water quality is reported because the effects of human activities are often more evident in rivers than they are in lakes.
The Alberta River Water Quality Index is included as a provincial performance indicator in the Alberta Government's Annual Report, "Measuring Up," published by the Ministry of Finance and Enterprise each June. Twelve sites from six major river systems are presented in that report.
A number of natural and human factors can influence Index values. These include the volume of river flow, local geology, climatic conditions, the degree of development along rivers, non-point sources of runoff (such as agricultural fields) and point sources of effluent that discharge into rivers. These factors are considered in the protection of water quality and aquatic ecosystems as part of the watershed approach outlined in Alberta's Water for Life Strategy. Using this approach, continuous improvements to river water quality may be expected as municipal wastewater treatment facilities and infrastructure are upgraded and as land use practices evolve. However, such enhancements can be offset by expanding human populations and intensified agricultural activity, combined with potentially lower river flows. Over time, the River Water Quality Index should reflect the impact of activities that significantly change water quantity or cause changes in inputs to rivers from either point or non-point sources.A brief history of the Alberta River Water Quality Index reporting from 1996 to present is presented here.
Which Index variables are most likely to not meet guidelines in surface water? What are the potential health effects of these variables?
The variables most likely to not meet guidelines are fecal coliform bacteria, phosphorus and nitrogen. Fecal coliform bacteria may indicate potential health risks to swimmers and may affect crop irrigation and livestock watering. Phosphorus is an important nutrient for plant growth but, if present in high concentrations, can also be responsible for the unsightly growth of nuisance algae and rooted aquatic plants. Total nitrogen, which includes ammonia, can also promote algal growth. In large quantities, however, it can be toxic to aquatic life and may render water unsuitable for livestock consumption and plant irrigation. Guidelines for these three variables are met more frequently upstream of developed areas than they are downstream.
Compliance with the total phosphorus guideline varies from year to year at all sites. Upgrades to wastewater treatment facilities in major centers such as Lethbridge, Calgary, Red Deer and Edmonton have helped decrease the total phosphorus downstream of these cities. For example, since Calgary's wastewater treatment plants began reducing phosphorus in their effluent in the 1980s, a noticeable change in phosphorus compliance has been seen in the Bow River downstream of Calgary. This guideline is currently exceeded far less frequently below Calgary than it was in the past.
Annual compliance with the total nitrogen guideline also varies naturally but is generally lower downstream of major centres. The total nitrogen guideline is almost always met in the North Saskatchewan and Bow rivers, upstream of Edmonton and Calgary.
Recent and planned upgrades to wastewater treatment facilities in a number of Alberta cities will help improve guideline compliance at downstream sites.
Numbers of fecal coliform bacteria almost always meet guidelines at sites upstream of Edmonton and Calgary. Downstream of these cities, the guideline value was often exceeded in the past. In more recent years, Calgary and Edmonton began to disinfect their wastewater with ultra-violet light. This resulted in improved compliance with the fecal coliform guidelines, as illustrated by the bacterial sub-index. Lower bacterial ratings downstream of Edmonton over the past four to five years appear to be driven by a variety of factors and are currently under investigation by Alberta Environment.Some water quality test results that do not meet relevant guidelines may reflect the impact of natural influences on water quality. During spring runoff, levels of nutrients and metals may exceed guidelines simply because these substances are present in soil and sediment washed into the river.
Which of the rivers identified in the Index have shown the most improvement or degradation? Why?
The River Water Quality Index has been calculated for data from April 1995 through March 2010. At most sites, overall index values reveal no clear tendency toward improvement or degradation. The majority of year-to-year differences are likely the result of natural variation in runoff and river flows. However, the addition of ultra-violet disinfection to Calgary's Fish Creek wastewater treatment plant in 1997 is reflected in improved bacterial sub-index values for 1997 to 2005 in the Bow River downstream of Calgary. Similarly, an upgrade to Edmonton's Gold Bar wastewater treatment facility in 1998 led to higher Index ratings for the North Saskatchewan River in subsequent years. More recent declines in the bacterial sub-index downstream of Edmonton, Red Deer, and Calgary appear to be linked to precipitation events and non-point source runoff.
A water quality monitoring site that has demonstrated substantial improvement in the past is the Oldman River upstream of Lethbridge. In 1995-96, this site was ranked as marginal, reflecting high river flows. In 2001-02, it was ranked as excellent. Because city storm drains influence this site, its water quality varies with the amount of runoff entering the river from the drains. Non-point source (e.g., agricultural) runoff also impacts the river. Dry conditions in the region lead to less runoff, resulting in reduced movement of contaminants from the land to the river. In a wet year or during a runoff event, conditions can again become fair or marginal. This is exemplified by the 2005-06 Index rating, which is largely related to significant summer rainfall events.
River Water Quality Index ratings for the 2009-10 reporting period remained very similar to the previous (2008-09) period, with all but three monitoring stations achieving ratings of good to excellent. Water Quality at three sites in the province, including the Athabasca River (at Athabasca), North Saskatchewan River (at Devon), and Red Deer River (u/s Red Deer) improved from good to excellent, while a single site on the Red Deer River (at Jenner) increased from fair to good.
Three provincial water quality monitoring stations received a rating of fair for the 2009-2010 reporting period. Of these, only the Oldman River at Highway 36, which received a rating of good for the previous (2008-09) period, demonstrated a decline in rating categories. This is likely due to a series of episodic rainfall events during the summer of 2009, which may have contributed to increased runoff and subsequent guideline exceedances for nutrients, pesticides, and bacteria in the river. The other two sites receiving ratings of fair are both located on the Battle River. Flows in the Battle River are typically very low, which provides limited dilution capacity. As a result of this and fairly intensive agricultural activity in the basin, the system tends to experience water quality guideline exceedances for nutrients, pesticides, and bacteria. Hence, the two monitoring stations on the Battle River have typically achieved Water Quality Index ratings of fair.
Why do Index results not show historical data before 1995?
An overall index value cannot be calculated for data prior to 1995, since pesticides were not part of the sampling program at that time. Long-term trends in overall index values will be difficult to assess until a few more years of data have been collected.
Trends over a longer time period can be statistically evaluated for individual water quality variables. For example, phosphorus removal technologies introduced to the City of Calgary's wastewater treatment plants in the early 1980s have led to decreased concentrations of this nutrient in the Bow River downstream of Calgary. Statistical analyses of trends for water quality variables measured at all the long-term river network stations are ongoing. Trend analysis results will provide a more in-depth picture of the complex state of water quality in Alberta rivers. This information is posted on the Alberta Environment Water website as it becomes available.
Some sites are reported as having 'excellent' water quality. Is it safe to drink this or any other surface water?
The Index refers to the condition of untreated surface water. Surface water should never be consumed without first being treated. Even so-called ‘pristine’ water can contain pathogens (microorganisms such as Giardia, Cryptosporidium, etc.) that may cause illness in humans. The source of these organisms is fecal matter from domestic and wild animals, as well as humans. Freezing will not kill these organisms. Any raw surface water can be contaminated and must undergo chemically-assisted filtration and disinfection as a minimum treatment for Alberta municipal waterworks systems.
Why is the Index reported for a fiscal year (March to April), rather than for a calendar year and why is it always more than a year old?
Because of the lengthy and complex process of sample collection, chemical analysis, data entry, Index calculation, and subsequent auditing, the Index can never be completely up-to-date and aligned with all government reporting. A fiscal year presentation allows us to be more current (i.e., 2005-06 data in 2007). The fiscal year also approximates a 'water year' (starting in Spring).
How does the Alberta River Water Quality Index differ from other WQ Indices used in the province (e.g., Oldman River Basin Water Quality Index)? Can numbers calculated for various water quality indices be compared?
A water quality index is simply a method for combining complex water quality data into a single number or statement. The index does not replace the conventional scientific process of analyzing and interpreting technical data. Alberta has made a significant contribution to the development of a Canadian Water Quality Index through its continued participation in a national technical sub-committee under the direction of the Canadian Council of Ministers of the Environment. The Canadian Water Quality Index has been officially identified by the National Round Table on Environment and the Economy as an indicator of freshwater quality, and the concept has already been applied in Alberta for a number of different purposes. These applications all use the same mathematical formula (calculation of scope, frequency and amplitude) but differ in the monitoring programs that support them, the variables and objectives they use, the format they are presented in and their specific purpose.
The Alberta River Water Quality Index is a department- and government-wide performance measure used to indicate the water quality at sites on major provincial rivers. The index formula has also been adapted for use specifically in the Oldman River and its tributaries as a reporting tool for the Oldman River Basin Water Quality Initiative. The Oldman Index uses fewer variables than the province-wide measure (no metals are included) and consists of a general index and a separate pesticide index. Index values calculated for the River Water Quality Index will not necessarily match those calculated at the same site using the Oldman method. However, each method should deliver a relatively consistent description of water quality at that site. For example, in 1998-99, the Oldman River at Highway 3 was given an overall index value of 89 (Good) using the River Water Quality Index method, and a general index value of 87 using the Oldman method.
Links to additional information: