Water quality overview of Athabasca River Basin

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  • This report overviews major water quality patterns and trends for the Athabasca River and its major tributaries. In doing so it compares water quality data with surface water quality objectives, identifies spatial and temporal patterns, defines major factors affecting water quality, characterizes the relationship between basin hydrology and water quality and identifies river reaches with similar water quality characteristics. The data analyzed for this overview assessment include historical water quality records collected since 1970 at three fixed station network locations (Jasper, Town of Athabasca and Ft. McMurray), and the results of six basin wide synoptic sampling surveys done seasonally during 1984 and early 1985. The historical data define long term trends, whereas the synoptic surveys provide information on spatial patterns. Results indicate that except for the St. Regis Pulp Mill at Hinton, point source effluents from municipal and industrial plants have no broadly based influence on river water quality. In almost all instances, tributary streams account for 90% or more of all measured constituent 1oadings. At low river flows the Hinton Pulp Mill does affect river water quality for a distance of 50 to 75 km. Many of the Alberta Surface Water Quality Objectives (ASWQUO) are regularly exceeded, however most of these exceedances are not attributable to point or nonpoint source impacts. These provincial objectives do not account for regional variations in natural water quality. Comparison with Environment Canada's use specific water quality objectives indicate Athabasca River water can be used for all beneficial uses except contact recreation, which is 1imited much of the year by low water temperatures and high turbidity. Certain objectives for aquatic life and wildlife are occasionally exceeded, however, these violations are due to natural causes and pending further investigation are not thought to be significant. Three water quality zones can be defined for the Athabasca River. The Foothills Reach, between Jasper Park boundary and Ft. Assiniboine, is characterized by fast flow and good overall water quality conditions. Alkalinity and hardness 1evels are elevated, reflecting the mountain origin of the water; yet the suspended solids, organic carbon and nutrient contents are low. The Hinton pulp mill is the only significant anthropogenic impact. Coal mining activity in the upper tributaries has no broad based effect on the mainstem river system. In contrast, very different water quality conditions are experienced in the river reach situated between Ft. McMurray and Lake Athabasca. Suspended solid 1evels are high much of the year, as are associated parameters like organic carbon, particulate nutrients and metals. These constituents are derived from upstream tributaries and channel re-suspension, rather than municipal or industrial effluents. The lower reach al so has a unique major ion chemistry created by 1oadings from the Clearwater River. The intermediate reach between Ft. Assiniboine and Ft. McMurray is a transition zone. Along this stretch, alkalinity and hardness levels decrease, while most other constituent concentrations increase due to tributary loadings. Based upon statistical analysis of the historical water quality database three distinct water quality seasons are defined. These include the ice cover interval, and two open water periods, from ice off to July 31 and August 1 to freeze-up. Water quality in the early openwater season is controlled by local and mountain snowmelt runoff and a rising hydrograph. The 1ate openwater season is affected by a falling hydrograph, summer rainstorms in the Interior Plains and maximum instream biological activity. Except for some tributaries the existing database adequately defines baseline water quality conditions throughout the basin. Future work should emphasize expansion of the fixed station water quality monitoring network, definition of river assimilation processes, development of basin specific water quality objectives, further work on trace organic compounds and more detailed definition of parameter inter-correlation and discharge dependence.

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