ECCC Main Stem Water Quality

Athabasca River (includes sites M2, M3, M4, M5, M6, M7 [2011-March 2018]) Water quality chemistry data for 17 sites in the lower Athabasca River (LAR), the Peace and Slave rivers, and their tributaries, including measurements of major ions, nutrients, metals (dissolved and total) and organics (including BTEX, cyanide and polycyclic aromatic hydrocarbons (PAHs).

An interpretive report (Glozier et. al., 2018) was released in 2018, which included assessments of the water quality status and trends for data from 2012-2015. An excerpt from the executive summary is provided below and the full report can be found online at https://open.alberta.ca/publications/9781460140284

“During the three year JOSM period, over 1300 water quality samples were collected from 21 locations representing a nearly 5-fold increase in overall sampling effort in the Lower Atahbasc river (LAR), Peace River (PR), Slave River (SR) and Peace Athabasca Delta (PAD). Status and spatial patterns among sites were examined for each parameter type including major ions, nutrients, mercury, and metals.

The major spatial patterns of interest included:

1. Extensive overlap in concentration of major ions, mercury, nitrogen and carbon along the LAR and main stem sites within the PAD;

2. Extensive overlap in concentration for metals along the LAR but a range of patterns among PAD mainstem sites.

• The most common pattern showed consistent concentration values for all main stem sites from the LAR at M3 though to the outlet of the SR at SL2.

• Similar to above, a second pattern showed similar concentrations along the length of the LAR main stem through to the interconnecting channel (i.e., M3-M10), but various patterns along the remaining main stem locations.

1. Range of concentration for parameters among the PAD tributary sites.

• In general, concentrations of metals, phosphorus and mercury in the McIvor and Birch rivers were higher than the other tributaries. Given the highly variable nature of water chemistry within and between PAD tributary sites, ongoing sampling will be required to adequately characterize the status and patterns of these new sites.

1. Patterns in phosphorus concentration

• Along the course of the LAR, the largest step increase for phosphorus occurred between M2 and M3, with concentrations remaining similar from M3-M9.

• Dissolved phosphorus values in the PR (M12) were the lowest; with the SR (M11A-SL2) appearing to be a mixture of the differential concentrations of the two main contributors.

1. Patterns in dissolved selenium

• In contrast to patterns discussed for other parameters, dissolved selenium concentrations showed statistically significant gradual increases in concentration between M3 and M6 after which concentrations stabilised at downstream sites (M7-M9). This pattern was dependent on the time year and most evident under high flow conditions during freshet.

All but one parameter had consistent concentrations along the main stem of the LAR from M3 to the downstream site M9. Thus, spatial patterns (other than for dissolved selenium) that were observed were attributed to changes in non-oil sands related inputs such as municipal or other industrial inputs or differences in geological sources. The increasing dissolved selenium pattern from M3-M6 may be linked to higher tributary inputs during freshet as reported by Chambers et al., 2017.

Seasonal patterns and temporal trends examined showed:

1. Typical seasonal patterns in water quality concentration included dissolved parameters exhibiting a pattern inverse to the hydrograph (with minimum concentrations occurring during high discharge periods and maximum concentrations occurring in low flow, under ice) while particulate associated parameters generally had higher concentrations during high flow spring/summer periods when suspended sediment loads were high.

2. Long-term trend analysis on data from M9 showed that, for the most recent period (2000-2014), several parameters including dissolved phosphorus and ammonia exhibited reductions in concentration while total phosphorus concentrations (which previously had been increasing) are now stable. Several changes in anthropogenic inputs are associated with these trends and include upgrades to facilities and the subsequent reductions to total loadings within the Athabasca River basin.

3. For several major ions and dissolved metals which displayed increasing trends at M9, results were similar when we examined trends at other sites in northern areas of Canada not directly downstream of the OSMA. As such, the increasing trends reported may have a broader regional pattern and are thus not likely directly related to upstream oil sands activities.

Evaluation of the data against 39 water quality guidelines revealed that nineteen of the parameters showed no values above guidelines (i.e., no exceedances). Some metals (namely iron and aluminum) commonly (>75%) showed values higher than the guideline, particularly during periods of high suspended sediment concentrations. Total mercury samples showed occasional (<6%) exceedances but, similar to total metals, these values were associated with high suspended sediment values. Site specific guidelines may be more appropriate and provide a better warning of changes to water quality, particularly for parameters which are associated with the commonly occurring high suspended sediments."