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What Does the Index Show?

Water quality can be expected to vary 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, which in turn results in less movement of contaminants from the land to the river. However, most persistent trends can be linked to human influence. Any activity that changes water quantity or affects inputs from either point sources (e.g., sewage outfalls) or non-point sources (diffuse sources; e.g., agricultural run-off) will influence water quality.

Upgraded municipal wastewater treatment has generally improved water quality downstream of major cities, such as Lethbridge, Calgary, Red Deer, and Edmonton; the Bacterial sub-Index reflects this improvement.

River Water Quality Index Results for 2005-2006 PDF 16KB

Alberta River Water Quality Index Map (2005-2006)

Alberta River Water Quality Index Map - Pesticides (2005-2006)

Alberta River Water Quality Index Map - Bacteria (2005-2006)

Alberta River Water Quality Index Map - Nutrients (2005-2006)

Alberta River Water Quality Index Map - Metals (2005-2006)

River Water Quality Sub-Index Values for Northern and Southern Rivers (2005-2006) PDF 14KB

River Water Quality Index Graphs (April 1995 – March 2006) PDF 20KB

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How is the Index Used?

The 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 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 each June. Twelve sites from six major river systems are presented in that report. The Index also appears in the Ministry of Environment's "Annual Report".

Alberta Government Annual Report 2006-07: Measuring Up.

Alberta Environment Annual Report 2005-06.

A number of natural and human factors can influence Index values: 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 the Government of Alberta's Water for Life Strategy. Using this approach, continued 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 populations and intensifying agriculture, combined with potentially lower river flows. Over time, the River Water Quality Index should reflect activities that significantly change water quantity or cause changes in inputs to rivers from either point (discrete) or non-point (diffuse) sources.

A brief history of the Alberta River Water Quality Index reporting from 1996 to present is presented here.

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Frequently Asked Questions

Which Index variables are most likely to not meet guidelines in surface water? What are the potential health effects of these variables?

The variables that are 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 the suitability of water for 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 cause algal growth. In large quantities, however, it can be toxic to aquatic life and may render water unsuitable for livestock and plant consumption. Guidelines for these three variables are met more frequently upstream of developed areas than downstream.

Compliance with the total phosphorus guideline varies from year to year at all sites. However, upgrades to wastewater treatment facilities in major centers such as Lethbridge, Calgary, Red Deer, and Edmonton have generally helped decrease the amounts of 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 had been in the past.

Yearly 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 likely 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 recent years, however, Calgary and Edmonton have begun to disinfect their wastewater with ultra-violet light. This has generally resulted in improved compliance with the fecal coliform guidelines, as illustrated by the bacterial sub-index. Lower bacterial sub-index ratings downstream of Edmonton over the past 3-4 years appear unrelated to municipal wastewater treatment and are currently under investigation by AENV

It is important to note that some water quality test results not meeting relevant guidelines may reflect the impact of natural factors on water quality. During spring runoff, for example, levels of nutrients and metals in undisturbed river reaches may exceed guidelines, simply because these substances are present in soil and sediment that is 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 2006. At most sites, overall index values reveal no significant overall improvement or degradation over this time period. 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 the present 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. A recent decline in the bacterial sub-index downstream of Edmonton appears unrelated to wastewater treatment at Gold Bar and is currently the subject of investigation by AENV.

Another site that has shown substantial improvement 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, and from non-point source (e.g., agricultural) runoff. Dry conditions have led 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.

In the current (2005-2006) reporting period, rivers in central and southern Alberta, including the North Saskatchewan, Red Deer, Bow, Oldman, and Milk, have shown a general decline in Index ratings relative to previous years. This is primarily a result of significant rainfall events during the summer of 2005. Such events are typified by increased surface runoff or overland flow, which tends to collect nutrients, bacteria, metals, and other materials as it travels. These potential contaminants, which may be naturally occurring or of human origin, are ultimately deposited in receiving rivers as non-point source effluents. If water is sampled during such a high flow event, chemical analyses will detect higher concentrations of a variety of these substances, many of which may exceed guidelines. Hence, the Index rating may be affected.

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 period can be statistically evaluated for individual water quality variables. For example, phosphorus removal at the City of Calgary's wastewater treatment plants in the early 1980s has lead to decreased concentrations of this nutrient being detected in the Bow River downstream of Calgary. Statistical analysis of trends for water quality variables measured at all the long-term river network stations is 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 from human sewage. 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., Alberta Agricultural Water Quality Index, 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 narrative statement. However, the index is not meant to 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 (CWQI) through its continued participation in a national technical sub-committee under the direction of the Canadian Council of Ministers of the Environment (CCME). The CWQI has been officially identified by the National Round Table on Environment and the Economy (NRTEE) 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 (RWQI) is a department- and government-wide performance measure that is used to indicate the relative water quality at sites located 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 RWQI will therefore 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 RWQI method, and a general index value of 87 using the Oldman method.

Alberta Agriculture and Food (AAF) is also using the CWQI formula in its application of the index concept to small streams in agricultural watersheds. The AAF (Alberta Environmentally Sustainable Agriculture; AESA) method, which has an agricultural focus, uses variables, objectives, and a classification scheme that differ from both the Alberta and Oldman Indices. Again, care should be taken to avoid direct comparisons between these different indices.

Links to additional information:

CCME Water Quality Index Website.

Alberta's State of the Environment Website.

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