Tributary Water Quality - Oil Sands Region

Water Quality Monitoring on Tributaries in the Athabasca River Oil Sands Region

Ells River (EL1, ELLS RIFF 2, ELLS RIFF5 [2012-2015]) Mackay River (MA1 [2012-2015], MA2 [2013-2015]) Steepbank River (STB RIFF1, STB WSC, STB RIFF7, STB RIFF10 [2012-2015]) Firebag River (FI1, FI WSC [2012-2015]) Muskeg River (MU1 [2012-2015]), MU6 [2012-2015]), MU7 [2012]) High Hills River (HIHI1 [2013-2015])

Water quality of tributaries in the Athabasca River oil sands region is heavily influenced by the presence of the underlying Cretaceous bedrock, which is comprised of shale, sandstone and limestone. The waters are moderately hard (average alkalinity of 114 mg l-1 CaCO3) because of their mineral content, particularly magnesium (average 8.62 mg l-1), calcium (average 28.06 mg l-1) and bicarbonate (138.53 mg l-1). This mineral content results in an average conductivity of 245 +/- 4 µS cm-1 and total dissolved solids concentration of 140 +/- 2 ppm. Concentrations of nitrogen and phosphorus (indicators of nutrient status) are typically low to moderate, averaging 0.14 mg l-1 total phosphorus, 0.03 mg l-1 total dissolved phosphorus, 0.92 mg l-1 total nitrogen, 0.09 mg l-1 nitrogen as nitrate+nitrite, and 0.04 mg l-1 nitrogen as total ammonia.

Seasonal variation for the majority of water quality constituents within the Athabasca tributaries can be strong and is highly reflective of hydrological discharge (i.e., highest concentrations typically occur during snowmelt periods, especially for parameters that are bound to particulate matter). Spatial variation of parameters within tributaries general showed an increasing trend from upstream of development to samples collected downstream of development (near mouth of a tributary).

Of the 45 water quality constituents (physical characteristics, major ions, metals, metalloids, selenium) and 52 Polycyclic Aromatic Compounds (PACs) analyzed, 28 have Guidelines for the Protection of Aquatic Life (Canadian Council of Ministers of the Environment – CCME). Only a few parameters were classified with frequent exceedances (i.e., >10% of of the approximately 1430 samples): total iron, 99% of all samples; total aluminum, 61%; total suspended solids, 39%; and total copper, 17%. All measurements of total mercury were below the CCME guideline; only pyrene from the PACs showed occasional exceedances (2% of samples) for established guidelines. Exceedances of guidelines are not uncommon in many river systems within and outside of the Oil Sands region and, in general, are associated with high flow events when suspended solids and contaminant loads are the greatest. High concentrations of suspended sediment (measured as total suspended solids) were observed during high flow events, such as occur during snowmelt and summer rainfall events. The high percentage of exceedances for iron was expected as these waters are known to have naturally-occurring high concentrations of iron.

Mercury in Tributaries

This data set includes river water concentrations of total mercury (THg; all forms of mercury in a sample) and methyl mercury (MeHg; the form of mercury that bioaccumulates through food webs) in five Athabasca River tributaries (Ells, Steepbank, Firebag, Muskeg and MacKay rivers).

No samples exceeded the Canadian Council of Ministers of the Environment guidelines for THg and MeHg.