Cumulative effects are defined by the Canadian Council of Ministers of the Environment (CCME, 2014, p.1) as “a change in the environment caused by multiple interactions among human activities and natural processes that accumulate across space and time”. In partnership with the Northwest Territories Cumulative Impact Monitoring Program (NWT CIMP), a division of the Government of the Northwest Territories, this project was designed to provide a better understanding of cumulative effects to water quality in the Upper Coppermine River basin. A better understanding of impacts due to current or past natural or anthropogenic disturbances, along with an accurate geochemical baseline, will provide policy makers and stakeholders, with the knowledge and skills required to monitor and manage future impacts to water quality in the Upper Coppermine.
This project had three overall objectives: 1) to determine the current state of knowledge of cumulative effects to water quality in the Upper Coppermine and similar regions by conducting a systematic literature review; 2) to establish baselines for key water quality parameters in the Upper Coppermine River basin using nearly 20 years of water quality data supplied by the Government of the Northwest Territories’ department of Environment and Natural Resources (GNWT ENR); and 3) to evaluate a cumulative effect indexing tool, previously developed for NWT CIMP, using information from the first two objectives. Findings from each of these three objectives are detailed in the three separate chapters of this report.
The first chapter details results of the first objective. They showed a lack of published literature specific to cumulative effects to water quality in the Upper Coppermine, and highlighted the need for more research. However, cumulative effect research in similar regions provided valuable insight and transferrable knowledge useful for our understanding of the Upper Coppermine. A broad search using Web of Knowledge publications, referencing similar ecozones to the Upper Coppermine, and a range of impacts, returned 42 results. The majority of those publications focus on effects from climate change such as permafrost thaw. A small proportion of studies report effects due to mining and road building. Future monitoring strategies should pay attention to increases in major ions, DOC and pH in surface waters, which have been shown to arise as a result of permafrost slumping in the basin. Further, increases in conductivity might indicate impacts from road building, while increases in strontium might signify diamond mine effluent.
To address the second objective, an ambient baseline was determined for 25 water quality parameters at four major lakes in the Upper Coppermine: Daring Lake, Desteffany Lake, Lac de Gras and Rocknest Lake. The ambient baselines were determined using two non-parametric statistical techniques: Tukey’s Inner Fence and Median+2MAD. The baseline results can be used by the NWT CIMP to monitor the levels of these parameters in future sampling programs in the Upper Coppermine and to identify potential exceedances at these lakes. A Mann-Kendall trend analysis was also completed for each parameter at each lake. The results show significant increases in strontium, chloride, sodium, pH and conductivity at Lac de Gras and Desteffany Lake. It is hypothesized that the changes are caused by the upstream anthropogenic (diamond mining) activity in the Lac de Gras sub-basin.
Finally, the third chapter details the results of an evaluation of the cumulative effect indexing tool, developed by Ecofish Research Ltd. for the NWT CIMP to predict cumulative impacts on water quality. The tool uses spatial data on various anthropogenic and climate change-induced disturbances, as well as a lake vulnerability metric, to predict spatial variation in cumulative impacts to surface waters. The evaluation compared the predicted output from the tool (high, medium, or low relative risk of cumulative impact for individual lakes) with the observed water quality data analyzed in Chapter 2 for the baseline assessment. The tool predicts that Daring Lake and Desteffany Lake have a low cumulative effect risk, and Lac de Gras has a high cumulative effect risk. The observed long term water quality data indicates that Daring Lake has a low cumulative effect risk, but suggests that both Desteffany Lake and Lac de Gras share a medium risk due to long term changes in certain parameters. It appears that the both the tool and long-term water quality data lack evidence of natural disturbances at these lakes and therefore most risk is from anthropogenic activity. It is recommended that a permafrost slump metric is added to the natural disturbance category of the tool.
Ultimately, the analyses undertaken in this report aids the NWT CIMP in understanding cumulative impacts to water quality in the Upper Coppermine. The report identifies and summarizes current knowledge; creates a baseline for certain water quality parameters which can be used to identify future changes and as a threshold to identify future exceedances; and evaluates a cumulative effect indexing tool being used by the NWT CIMP.