What does the indicator show?
In 2005-2006, water quality ratings for LTRN sites on major rivers in Alberta ranged from fair to excellent. In general, rivers in the northern part of the province, including the Smoky, Wapiti, Peace, and Athabasca, demonstrated good to excellent water quality. Central and southern sites, including those on the North Saskatchewan, Battle, Red Deer, Bow, Elbow, Oldman, South Saskatchewan, and Milk Rivers had fair to good Index ratings. Overall, Index ratings for 10 of 24 LTRN sites increased over the previous (2004-2005) reporting period, while12 decreased, and two remained unchanged. Decreases, the majority of which occurred in rivers south of the Athabasca, can be directly linked to major rainfall events in 2005. When they occur, such events may cause significant overland flow, raising the relative contribution of non-point source runoff to rivers and other surface waters. As it travels overland, this runoff may collect nutrients, bacteria, metals, and other contaminants, which are subsequently introduced to the receiving river. Although some of these contaminants may be attributable to human activities in a given river basin, many occur naturally in soils.
Over the long term, Index values show no discernible tendency towards degradation in water quality. In the case of some northern rivers (Athabasca, Peace, Smoky), 2005-2006 Index scores for both upstream and downstream sites are higher than those for the previous year, likely because of reduced precipitation and associated flow. Less precipitation results in reduced surface runoff and, therefore, decreased movement of materials from the land to the water in some areas. During times of elevated flows, as experienced by the more southerly rivers during 2005, lower ratings can be expected due to increased movement of potential contaminants, whether naturally occurring or as a result of human activity, from the land to the water.
A number of natural and human factors can influence Index values. Flow volume, climatic conditions, local geology, degree of development in the basin, non-point sources of runoff (such as agricultural fields), and point sources of effluent can all affect water quality ratings. For example, during spring runoff, concentrations of nutrients and metals may exceed guideline values, even in “natural” areas, simply because these substances are present in soils that are washed into rivers.
Water quality tends to be poorer downstream of areas with significant urban, industrial, or agricultural development. However, in recent years, substantial improvements in water quality below major developments have resulted from enhanced point source control. This is reflected by higher index values downstream of some of Alberta’s major centres. To view charts showing index ratings for multiple Alberta rivers over the past several years, click here.
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Why is this indicator important?
The River Water Quality Index is an environmental indicator that summarizes chemical, biological, and physical data into a simple composite descriptor of water quality. The Index is not meant to replace the conventional scientific process of analyzing and interpreting technical data, but does provide a standardized index of annual water quality conditions in various rivers of the province. The purpose of the RWQI is to show relative differences between sites and over time, and to help identify degradation or improvement that may have a human cause.
Note that the River Water Quality Index evaluates water quality only and does not describe sediment quality, aquatic biota, or habitat conditions in Alberta rivers. Aquatic biota can be influenced by a number of factors that are not accounted for in this index. For this reason, the RWQI is not a comprehensive indicator of overall aquatic ecosystem health.
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What actions are being taken?
A number of natural and human factors can influence index values. These include the volume of river flow, climatic conditions, local geology, the degree of development along rivers, non-point sources of runoff (such as agricultural fields), and point sources of effluent that discharge into rivers. Alberta's Water for Life strategy intends that all these factors will be considered in the protection of water quality and aquatic ecosystems, as part of the watershed approach. In keeping with this approach, continuous improvements to river water quality are being pursued through upgrades to municipal wastewater treatment facilities and infrastructure, through enhanced land use practices, and via various other means.
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