Oil Sands Monitoring Program Technical Report Series

Assessments of Groundwater Influence on Selected River Systems in the Oil Sands Region of Alberta

1.5 Report Series

Assessments of Groundwater Influence on Selected River Systems in the Oil Sands Region of Alberta

G. Bickerton¹, J.W. Roy¹, R.A. Frank¹, J. Spoelstra¹, G. Langston2, L. Grapentine¹, and L.M. Hewitt¹

¹Environment and Climate Change Canada 2Alberta Environment and Parks

This publication can be found at: https://open.alberta.ca/publications/9781460140291

Recommended citation: Bickerton, G., Roy, J.W., Frank, R.A., Spoelstra, J., Langston, G., Grapentine, L. & L.M. Hewitt. . 2018. Assessments of Groundwater Influence on Selected River Systems in the Oil Sands Region of Alberta. Oil Sands Monitoring Program Technical Report Series No. 1.5. 32 p.

June 2018 ISBN 978-1-4601-4029-1

ForewordSince February 2012, the governments of Alberta and Canada have worked in partnership to implement an environmental monitoring program for the oil sands region. In December 2017 both governments renewed their commitment to working together with Indigenous communities in the region by the signing the Alberta-Canada Memorandum of Understanding (MOU) Respecting Environmental Monitoring in the Oil Sands Region. The MOU establishes the foundation for an adaptive and inclusive approach to program implementation ensuring that the program is responsive to emerging priorities, information, knowledge, and input from key stakeholders and Indigenous peoples in the region.

The Oil Sands Monitoring Program is designed to enhance the understanding of the state of the environment and cumulate environmental effects as a result of oil sands development in the region though monitoring and publically reporting on the status and trends of air, water, land and biodiversity. Its vision is to integrate Indigenous knowledge and wisdom with western science to design, interpret, assess, report and govern the program.

Canada and Alberta have provided leadership to strengthen program delivery, and ensure that necessary monitoring and scientific activities meet program commitments and objectives. The oil sands industry provides funding support for the program under the Oil Sands Environmental Regulation (Alberta Regulation 226/2013). Key findings and results from the program inform regional resource management decisions and importantly, are considered as an objective source of scientific interpretation of credible environmental data.

A mandated cornerstone of the program is the public reporting of data, status and trends of environmental impacts caused by development of oil sands resources. The Oil Sands Monitoring Program Technical Report Series provides an objective, and timely, evaluation and interpretation of monitoring data and information collected across environmental media of the program. This includes reporting and evaluation of emission/release sources, fate, effects and transport of contaminants, landscape disturbance and responses across theme areas including atmospheric, aquatic, biotic, wetlands, and community based monitoring.

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Executive Summary

In 2011, the Governments of Canada and Alberta designed a monitoring plan for surface water quality and quantity, air quality and biodiversity of the lower Athabasca River, its tributaries, and downstream receiving environments. The plan, known as the Joint Oil Sands Monitoring Plan (JOSM), included a groundwater component aimed at gaining a better understanding of groundwa-ter-surface water interactions in the region — knowledge essential for developing a comprehensive program that includes surface water quality/quantity and aquatic ecosystem health impacts.

The groundwater component was composed of two sub-themes. Sub-theme A investigated ground-water-surface water interaction to build an understanding of this process in the oil sands region in order to address the monitoring question:

What is the relative importance and contribution of groundwater quality and quantity to surface waters?

The goal of this sub-theme was to evaluate, develop and test methods and techniques for identify-ing locations of significant groundwater input to selected major tributaries of the Athabasca River and to quantify/constrain the contribution of groundwater and mass-loading to individual reaches.

Sub-theme B focused on evaluating potential tailings pond leakage, addressing the monitoring question: Is there groundwater seepage from tailings ponds and/or other oil sands industrial operations entering the surface water system?

In this sub-theme, the potential risk of discharging groundwater adjacent to an oil sands tailings pond, compared to other groundwater in the area, was assessed. In addition, a suite of chem-ical analyzes were developed and tested for their ability to distinguish oil sands process water (OSPW)-affected groundwater.

The methods and assessment approach developed in sub-theme A demonstrated a capacity to identify critical locations and regions of groundwater input and obtain estimates/constraints of groundwater discharge at the reach scale. To date there have been no other studies in the region to provide information on the nature of groundwater-surface water interactions at the reach scale. The approach provides a relatively rapid assessment of the role and importance of groundwater discharge to a river by providing information on where, and where not, aquatic habitat and sur-face water quality may be most vulnerable to changes in quality and quantity of groundwater dis-charge. This information can be used to identify critical areas to include in groundwater monitoring plans and to help design and inform surface water and aquatic health monitoring programs so that groundwater influences may be properly integrated and evaluated. For the MacKay River, it was estimated that direct discharge of groundwater through the riverbed of the study area provides a small but significant contribution (~2-10 % of fall low flow) to the total river flow during open water periods but perhaps 100 % of under ice flow. The full ecological importance of this remains unclear but presumably groundwater will be important in maintenance of thermal regimes favour-able to biota and preservation of aquatic habitat during under ice periods.

Results to date in sub-theme B suggest that generally there is no broad-scale increased risk posed to aquatic life from groundwater discharging adjacent to Suncor’s Pond 1 in comparison to other nearby areas. However, there are indications that groundwater influenced by oil sands process- affected water from the tailings pond is reaching the Athabasca River sediments beside Pond 1 at several locations. Whether these locations are experiencing localized ecological impairments has not yet been assessed.

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Studies conducted under the groundwater theme were developed to address science needs and knowledge gaps related to groundwater-surface water interactions on the Athabasca River trib-utaries and proximate to tailings ponds. This work was not intended to serve as a monitoring activity or a template for monitoring, but rather to provide foundational assessments to inform and guide development and interpretation of future monitoring activities and initiatives related to water quality, water quantity and ecological health. The findings of this study will provide context for surface water quality and regional hydrology interpretations and, with further component inte-gration, will contribute to the assessment of ecological effects. Locations of groundwater discharge may also be considered for their role as thermal refugia for fish and other aquatic species that may influence their survival during hot, dry summers or over winters (by preventing freezing into the river sediments). The two groundwater sub-themes were designed to address two independent groundwater issues and consequently there was no direct integration among sub-themes. While a significant amount of data has been interpreted for this report, there is further data analysis and interpretation required. Consequently, this synthesis report comprises an overview and activity re-port for the two subthemes with additional information to be disseminated by future reports and/or publications.

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Table of Contents

List of Tables ........................................................................................................................ ivList of Figures .......................................................................................................................v1. Introduction ......................................................................................................................12. Sub-Theme A: Groundwater Contributions to Tributaries ...............................................3

2.1 Background ......................................................................................................................32.2 Objectives ........................................................................................................................42.3 Methods ............................................................................................................................5

Overview of Study Design ................................................................................................................5Water Balance Methods ...................................................................................................................6Other Field Methods ........................................................................................................................8Statistical Approaches Applied to Flow Data .....................................................................................8ADCP Measurement Uncertainty ......................................................................................................8

2.4 Results and Discussion .....................................................................................................9Water Balance Methods ...................................................................................................................9

2.5 Summary and Conclusions .............................................................................................163. Sub-Theme B: Potential Tailings Pond Leakage ............................................................17

3.1 Background ....................................................................................................................173.2 Objectives ......................................................................................................................183.3 Methods ..........................................................................................................................193.4 Results and Discussion ...................................................................................................21

Objective (1): Potential Risk to Aquatic Life .....................................................................................23Objective (2): Diagnostic Characteristics of OSPW ..........................................................................23Objective (3): Does OSPW discharge to the Athabasca River ............................................................25

3.5 Summary and Conclusions .............................................................................................254. Theme Assessment .........................................................................................................26

4.1 Integration with other Themes of the Water Component ..............................................264.2 Future Research Needs in Support of Monitoring .........................................................264.3 Monitoring Recommendations .......................................................................................27

5. Acknowledgements ........................................................................................................286. Literature Cited ..............................................................................................................29

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List of Tables

Table 1. Overview of groundwater-surface water activities.

Table 2. Description of the various sets of groundwater and other types of water samples collected. 19

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List of Figures

Figure 1. Geographic scope of sub-theme A.

Figure 2. MacKay River study reach (i.e., from confluence of the Dunkirk River downstream to the con-fluence of the Dover River) and locations of the 12 river cross-sections used for ADCP-based flow and stage measurements.

Figure 3. Historical stage of the MacKay River at Government of Canada hydrometric station 07DB001 (August 2014 to August 2015) showing the general river conditions during the (a) August 2014, Sep-tember 2014 and March 2015 flow measurement campaigns; (b) August 2014, September 2014 flow measurement campaigns; and (c) the timing of the flow measurements at various river cross-section during September 2014.

Figure 4. Locations of the 44 lower-order tributaries contributing surface water to the MacKay River along the 125-km study section.

Figure 5. Mean river flows and 95 % confidence intervals from the September 2014 and March 2015 measurement campaign.

Figure 6. River interval gains in flows and associated 95 % confidence intervals for the Mackay River and the contribution of lower-order tributaries to the interval flow gains for the September 2014 mea-surement campaign. (Note: Interval Flow Gain plotted at mid-point of interval).

Figure 7. River interval gains in flows and associated 95 % confidence intervals for the Mackay River and the contribution of lower-order tributaries to the interval flow gains for the March 2015 measure-ment campaign. (Note: Interval Flow Gain plotted at mid-point of interval; unlabelled lines representing intermediate sections not measured in March 2015 retained for reference).

Figure 8. Cross-section of study tailings pond (dyke and tailing deposition; Pond 1). Modified after Hunter (2001).

Figure 9. Plan view of study tailings pond (Pond 1) showing drainage collection system. Modified after Hunter (2001).

Figure 10. Areas of groundwater sampling within the oil sands area for Part 1: a) zones EL, MR, SB, consisting of tributaries of the Athabasca River, b) inset showing zones NW, NE, EP, SW along the Athabasca River, and c) inset showing the 4 pond-site zones (PA, PB, PC, PD) beside the study tailings pond. Reproduced from Roy et al. (2016), with permission from John Wiley and Sons Publishers.

Figure 11. Map depicting sampling locations of OSPW, near-field and far-field locations prioritized for detailed profiling, as a component of Part 2. Inset depicts close-up of area illustrating locations of Site B near-field drive-points, interceptor and monitoring wells. Reprinted with permission from Frank et al. (2014) Profiling oil sands mixtures from industrial developments and natural groundwaters for source identification. Environ Sci Technol 48: 2660-2670. Copyright (2014) American Chemical Society.

Figure 12. Box-whisker plots showing the quartile range comparison of the 20 guideline compound concentrations in shallow groundwater between non-pond (-np; those away from any tailings ponds) versus pond-site (-ps; those adjacent to the tailings pond of interest) samples. Dashed line indicates the aquatic life guideline value or (two lines) range (CCME 2007). Asterisk denotes data set is significantly higher (p< 0.05; Mood’s Median Test). Note the differences in scales and breaks of the y-axes.

Figure 13. GCxGC-TOF/MS ion chromatograms for select samples from OSPW, far-field (drive point 1) and near-field (drive-point 4) sites. Shown are the mono-aromatic m/z 145 (Family A) and m/z 237 and 310 (Family B) ions (see Frank et al. (2014) for exact retention times). Reprinted with permission from Frank et al. (2014) Profiling oil sands mixtures from industrial developments and natural groundwaters for source identification. Environ Sci Technol 48: 2660-2670. Copyright (2014) American Chemical Society.

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Figure 14. Locations of groundwater samples collected in zones PA and PB; those in red are likely OSPW- affected (Part 2; Frank et al. (2014)); those in yellow are the suspect set identified in Part 1 (Roy et al. 2016); those in green are likely non-affected by OSPW.

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1. IntroductionPrior to the Joint Oil Sands Monitoring Plan (JOSM), several scientific reviews (e.g., CEMA 2010; RSC 2010; ATIF 2011) had found knowl-edge gaps in our understanding of the role of groundwater in river ecosystems in the oil sands region. Addressing these gaps was deemed crit-ical for developing and operating cumulative effects monitoring programs to detect if, and to what extent, environmental impacts from the oil sands industry are occurring.

Environmental monitoring and land manage-ment plans require an understanding of how and where groundwater interacts with surface water systems to properly evaluate impacts of proposed and existing developments and iden-tify critical monitoring requirements. The trib-utaries of the Athabasca River and associated aquatic ecosystems are anticipated to be more vulnerable to changes in the quantity and qual-ity of groundwater discharge than the Athabas-ca River itself. This is largely due to the poten-tial for local groundwater to contribute a higher proportion of the total river flow, and may be particularly significant during under ice and low flow conditions. Concern was also expressed about the potential for groundwater affected by oil sands process water (OSPW) from tailings ponds to reach nearby rivers and impair aquatic ecosystems (RSC 2010). Past reports suggest-ed leakage of groundwater affected by oil sands processing to the Athabasca River (Baker 1999; Hunter 2001; Ferguson et al. 2009), which rais-es the potential for impacts on the river’s aquatic ecosystem. Thus, there is a need to assess the validity of these reports and the current eco-logical risk from OSPW-affected groundwater, considering that this information may influence plans for water quality and aquatic biota mon-itoring and interpretation of such monitoring data. However, this assessment is complicated by the current lack of definitive parameters for OSPW source attribution. Groundwater passing through natural oil sands deposits is expected to contain many of the same, or similar, com-pounds found in OSPW (a concentrated wash water of mined oil sands). Groundwater may also obtain constituents found in OSPW from other geological formations in the area (e.g., salts, metals), and from various anthropogenic sources (e.g., domestic waste; landfill, etc.). A primary knowledge gap is how to identify with strong certainty the presence of OSPW-affected

groundwater in river water receptors (including river waters, sediments and associated aquatic organisms), especially in cases where detailed on-site groundwater monitoring is not available. A related aspect of this knowledge gap is to as-sess possible impacts on aquatic ecosystems at locations where OSPW-affect groundwater was identified.

In developing the various elements of JOSM (Environment Canada and Alberta Environment 2011a, b; 2012), recommendations and con-clusions of previous monitoring reviews and re-ports were considered and incorporated where appropriate. It was recognized that assess-ments of the nature and role of groundwater interactions and connectivity with surface water ecosystems would be needed as foundational support to the water quality and aquatic ecosys-tem components of JOSM. The integrated and mass-balance principles used to develop the JOSM require a systematic and comprehensive quantification/evaluation of all sources and as-sociated fluxes of materials entering the various watersheds in the region. Understanding the role of groundwater and how and where it in-teracts with surface water ecosystems, and oth-er hydrological components, is a fundamental requirement for a comprehensive program that includes monitoring for surface water quality/quantity and aquatic ecosystem health impacts. Developing the tools and techniques required for assessing the current ecological risk from OSPW-affected groundwater was also identified as a specific aspect of groundwater-surface wa-ter interaction and a priority to be addressed.

The groundwater theme was composed of two sub-themes. Sub-theme A investigated ground-water-surface water interaction to build an understanding of this process in the oil sands region. In particular, this study aimed to address the monitoring question (Environment Canada and Alberta Environment 2011a):

What is the relative importance and contribution of groundwater quality and quantity to surface waters?

The goal of this sub-theme was to evaluate, develop and test methods and techniques for identifying locations of significant groundwater input to select major tributaries of the Atha-

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basca River and to quantify/constrain the con-tribution of groundwater and mass-loading to individual reaches. Methods were developed and assessed for their ability to provide infor-mation at appropriate scales and precision for informing, analyzing and guiding subsequent monitoring/assessment activities of all monitor-ing components that have some dependency on groundwater interaction with the river.

Sub-theme B focused on evaluating poten-tial tailings pond leakage and addressed the monitoring question (Environment Canada and Alberta Environment 2011a):

Is there groundwater seepage from tailings ponds and/or other oil sands industrial operations entering the surface water system?

In this sub-theme, the potential risk of dis-charging groundwater adjacent to the first and recently reclaimed oil sands tailings pond (Sun-cor’s Pond 1; initiated in 1960s) compared to other groundwater in the area was assessed us-ing field-collected samples. In addition, a suite of chemical analyzes was developed and tested for ability to distinguish OSPW-affected ground-water. These were then used to better assess the potential for groundwater affected by OSPW from Pond 1 to reach river sediments. The study focused on Suncor’s Pond 1 because of its ex-pected higher probability of OSPW migration (i.e., it is the oldest and closest to a major riv-er), with past reports suggesting leakage to the Athabasca River (Baker 1999; Hunter 2001; Ferguson et al. 2009). In addition, groundwater from around the Mildred Lake tailings pond and within its documented OSPW-affected ground-water plume (Oiffer et al. 2009) was included to provide broader testing of the chemical ana-lyzes suite.

Both studies were developed to address science needs and gaps related to groundwater-sur-face water interactions on the tributaries and proximate to tailings ponds. This work was not intended to serve as a monitoring activity or a template for monitoring but rather as an assessment (and proposed methodologies for conducting such assessments) to inform and guide development and interpretation of future monitoring activities and initiatives. Findings will inform monitoring strategies for water qual-

ity, water quantity and ecosystem health (ben-thos, fish) monitoring on rivers within the oil sands development area, and will be useful in identifying potential ecological cause-effect re-lationships.

Sub-themes A and B represent field studies for which the data acquisition phase is complete, but further analysis is required to complete in-terpretation of the collected field data. As such, this synthesis report comprises an overview and activity report for the two sub-themes with ad-ditional information to be disseminated within future reports and/or publications.

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2. Sub-Theme A: Groundwater Contributions to Tributaries

2.1 Background

Groundwater monitoring for various purposes has been occurring to some degree for decades in the oil sands region. The Alberta Geological Survey (AGS) and the Government of Alberta’s Groundwater Observation Well Network (GOWN) have operated several monitoring wells in the region, with many recently becoming reactivat-ed and incorporated into the NAOS (Northern Alberta Oil Sands) regional groundwater moni-toring network (CEMA 2010; AESRD 2013). Ad-ditionally, groundwater compliance monitoring, associated with provincial approvals and per-mitting, has been occurring at the site scale for each oil sands operation since the implementa-tion of Alberta’s Environmental Protection and Enhancement Act (EPEA) in 1993 (CEMA 2012). However, these historical and current groundwa-ter monitoring activities do not (nor were they designed to) directly address questions related to groundwater-surface water interactions.

Some general insight into the role and impor-tance of groundwater on surface water quality and quantity is available from various studies and monitoring programs in the region. The valleys of the Athabasca and Clearwater rivers in the oil sands area are known to be regional groundwa-ter discharge areas (AESRD 2013) and evidence of groundwater connections to surface through springs and seeps occurs throughout the region (Gue 2012; CEMA 2013; Gibson et al. 2013). Although groundwater monitoring was outside the mandate of the Regional Aquatic Monitoring Program (RAMP), annual technical reports (e.g., RAMP 2003; AEMERA 2015) clearly acknowl-edge and interpret the general degree to which groundwater influences the water quality and hydrological responses of Athabasca River trib-utaries. The RAMP reports consider watershed water yields, winter base flows, water balances and other hydrological parameters to infer the relative importance of groundwater discharge to select tributaries. They also suggest that of the four major tributaries interpreted the Firebag River has the largest contribution of ground-water, followed by the Steepbank, Muskeg and MacKay rivers. Based on their assumption that winter flows for all streams in the oil sands re-gion consist primarily of groundwater-fed base flow (RAMP 2003), the RAMP reports used winter

low-flow measurements to gain a sense of the order of magnitude of the expected groundwater discharge to the individual tributaries. Based on observed minimum winter flows, groundwater discharge for the Firebag, Steepbank, Muskeg and MacKay rivers, respectively, are estimated to range between: 4.24-11.8 m3/s (16-46 %); 0.022-0.498 m3/s (0.4-10 %); 0.040-0.480 m3/s (1-12 %); and, 0.023-0.845 m3/s (0.2-6 %) (RAMP 2003) with the percentage of mean annual flow (GOC 2016) provided in paren-theses for additional context. Alberta Environ-ment (2011) provided additional estimates from available information on groundwater discharge and reported the estimated groundwater dis-charge to the Athabasca, Firebag, Muskeg and Steepbank rivers to be, respectively, 44.5 m3/s (7 %); 7.15 m3/s (28 %); 0.00001-0.001m3/s (0-0.03 %); and 0.001 m3/s (0.03 %). Com-parison of the groundwater discharge estimates from these two sources show a similar estimate for the Firebag River but vastly different esti-mates for the Muskeg and Steepbank rivers. The reason for these apparent discrepancies is not immediately clear from the information pro-vided but may be due, in part, to differences in years analyzed, methods used to analyze/inter-pret, and/or length of data series.

Several field studies have attempted to quan-tify the flux of groundwater discharging to sur-face waters at various scales. Some studies ex-amined direct groundwater discharge to rivers (i.e., groundwater discharging directly to the river through river banks and sediments) while others have investigated total groundwater discharge (i.e., the sum of direct and indirect groundwater discharges where indirect refers to groundwater discharged to the lower order trib-utaries of the river). Jasechko et al. (2012) ex-amined the regional-scale (100 km–1,000+ km) contribution of saline groundwater (i.e., not all groundwater) discharge to the Athabasca River from deep regional groundwater flow systems. Using a chloride mass balance approach, they estimated the saline groundwater discharge for a reach extending 210 km downstream of Fort McMurray to be between 500 L/s to 3,400 L/s (i.e., approximately 0.1 % to 3 % of the river flow). At the local scale, Gue (2012) examined the contribution of localized saline groundwater springs along the banks of the Clearwater and

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Athabasca rivers and concluded that they pro-vide minimal contributions to the overall flow and mass loading to the river. Schwartz and Milne-Home (1982) used geochemical characteristics to estimate that groundwater contribution to the Muskeg and Firebag rivers varied seasonal-ly between 14-80 % and 2-65 % respectively. A recent regional study based on hydrograph separations using stable isotopes (Gibson et al. 2016), estimated that the total groundwater contributions to the Firebag, Steepbank, Mus-keg, MacKay and Ells rivers were, respectively, 44, 50, 39, 31 and 5 % of the average annual flows.

Except for the work of Schwartz and Milne-Home (1982) and Gibson et al. (2016), available in-formation relevant to evaluating groundwa-ter-surface water interactions on the tributaries is sparse and has been generally limited to dis-charge predictions from regional-scale ground-water modelling performed as part of Environ-mental Impact Assessments (EIAs) for specific mining developments. Many of these modelling reports and EIA documents provide no informa-tion on groundwater-surface water interactions and those that do generally provide only very limited information at a regional-scale for se-lect rivers or reaches. CEMA (2014) provides a review of groundwater modelling studies and an assessment of the potential cumulative im-pacts to groundwater and surface water in the MacKay River watershed. Estimates of ground-water discharge to the MacKay River range from 0.01-0.055 m3/s for existing conditions with predicted reductions to -0.001 to 0.043 m3/s once the various oil sands projects are devel-oped and operational. Therefore, model simu-lations of groundwater diversions in the MacKay River watershed have suggested the potential for reduced groundwater discharge to the riv-er and, in some instances, the potential for groundwater flow reversals (CEMA 2014). Ad-ditional modelling work was recently performed for the MacKay River Watershed using integrat-ed groundwater/surface water models to better understand the potential cumulative effects of water withdrawal and steam-assisted gravity drainage (SAGD) operations on surface water and groundwater quantity (CEMA 2016). How-ever, it is questionable how reliable such esti-mates of groundwater discharge are in terms of accuracy and precision when obtained from large-scale regional models without appropriate measurements of groundwater discharge avail-

able for calibration and validation. Obtaining new field data for model parameterization and validation was not within the scope of this latest modelling exercise (i.e., CEMA 2016).

Only a patch work of information provides in-sight regarding potential extent of groundwa-ter influence on selected rivers in the oil sands region. The information was obtained through various approaches and it is often applicable only to select portions of the rivers, making direct comparisons between studies difficult. Predictions of groundwater discharge obtained through numerical models are largely not val-idated with suitable field measurements and, consequently, contain significant uncertainty. Current estimates of groundwater discharge to surface water are generally only applicable at the watershed/river-scale and provide little in-formation on where groundwater discharges are most significant, how they are distributed along the river, and how groundwater discharge var-ies seasonally and annually. Reliable reach/lo-cal scale field information on groundwater-sur-face water interactions at appropriate time and spatial scales is needed to assess the ecological importance of groundwater (e.g., fish and ben-thic habitat maintenance, surface water quality, etc.) and to identify reaches that may be most vulnerable to changes in groundwater condi-tions (i.e., discharge and quality).

The first phase was to establish the fundamen-tal information necessary to make recommen-dations regarding specific groundwater-related needs to support the JOSM and the components linked to the potential input of groundwater. In this assessment, reliable reach/local scale groundwater and related surface water data at appropriate time and spatial scales were evalu-ated. This allowed for a preliminary assessment of the ecological importance of groundwater and identified reaches that may be most vulnerable to changes in groundwater discharge. Suitable field techniques were developed for collecting systematic and consistent field measurements with the best available precision.

2.2 Objectives

For the implementation stage of the JOSM, the objectives of sub-theme A were to establish and demonstrate field techniques that could pro-vide the necessary understanding of ground-water-surface interactions for the tributaries.

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Specifically, the study objectives included four elements:

• Develop and test assessment methods for evaluating the role and importance of groundwater in selected river ecosys- tems;

• Determine the nature (e.g. discrete versus diffuse) and distribution of ground- water discharge to selected rivers in the oil sands region;

• Identify, where possible, groundwater discharge areas that may have significant influence on river ecosystems; and

• Where possible, quantify/constrain groundwater discharge and mass loading at the reach-scale.

Approaches developed and assessments per-formed in this phase of JOSM are intended to guide and inform the next phases of monitoring and assessment in the program.

2.3 Methods

Overview of Study Design

The study design originally considered examin-ing large (40-150 km) sections of the five major tributaries of the Athabasca River that fell with-in the geographic scope of JOSM and the ac-tive surface-mining areas (i.e., the Ells, Firebag, MacKay, Muskeg and Steepbank rivers) (Fig. 1). Consistent with the adaptive philosophy of the JOSM, methods and techniques for achieving the study objectives evolved and were refined as new information was obtained in each year of the study. Methods and strategies were contin-ued, added or abandoned depending on circum-stances and observed conditions.

In the first year of study (i.e., 2012), all riv-ers were initially evaluated using available hy-drological information and field reconnaissance to determine suitable sampling times and ac-cess options. For rivers that met the logistical requirements (e.g., suitable accessibility), sec-tions of each river were selected for investiga-

Figure 1. Geographic scope of sub-theme A.

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tion. The sections were selected to ensure that the range of natural (e.g., geological forma-tions/surficial geology, land cover, lower-order tributary location) and developed (e.g., surface and in-situ mining) settings available along the river were included and that sufficient distance upstream of development was provided. Select-ing reaches/sections that covered the spectrum of river settings provided improved potential to evaluate and identify if discharging groundwa-ter quality/quantity was associated with partic-ular geological units or development settings.

Rivers that met the logistical requirements were initially screened using a multi-parameter geo-chemical tracer approach. Indications of ground-water influence were examined by sampling riv-er water at regular intervals (250–1,000 m) for stable isotope compositions of water (i.e., δ18O and δ2H), dissolved inorganic (i.e., silica, ma-jor ions, trace metals, dissolved oxygen) and physical parameters (i.e., temperature, electri-cal conductivity). To improve the ability to de-tect groundwater influence to the river, screen-ings were performed during open water periods at annual low-flow (typically late-August to late-September), when groundwater’s contribu-tion to total flow was expected to be relatively high. Geochemical screenings of each river re-quired one to three days to complete and were performed during periods of relatively stable river conditions (i.e., stable river levels and no significant precipitation immediately preceding or during the screening). Additionally, samples for isotopic and inorganic parameters were col-lected at fixed surface water stations as part of the surface water quality component during their year-round sampling program to provide an indication of the temporal changes of these parameters.

In year two of the study (i.e., 2013), the fo-cus was on exploring and testing methods for the ability to quantify or constrain groundwater discharge into rivers at the reach scales. Initial screenings, observations and experience from year one were used to guide and adjust river and reach selections for this phase of the study. Additionally, further geochemical screenings of select river reaches and shallow groundwater sampling were performed to confirm and com-plement findings from year one screening activ-ities.

The final year of the study involved a full-scale demonstration and evaluation of a selected riv-er (i.e., the MacKay River) using the proposed and developed methods for assessing ground-water-surface water interactions.

Water Balance Methods

The approach used to quantify the groundwater flux to rivers and determine the reaches where significant groundwater exchange is occurring was based on water balance principles. For the main channel, differential stream gauging (also known as seepage runs, water balance or the input-output method) was used as the primary approach. Differential gauging is a commonly employed method for quantifying net groundwa-ter-surface water interaction in streams (Kalbus et al. 2006). The method involves comparing flow measurements made at the upstream and downstream boundaries of each reach along the river. If all other sources and sinks for each reach can be accounted for, then differences in measured flows can be attributed to direct groundwater flux (and the accumulated uncer-tainty) to the reach. The water balance for dif-ferential stream gauging for a given reach can be described by:

QGroundwater = QRiver - QTributaries - QSources+ QSinks

where QGroundwater is net groundwater flux to the reach; QRiver is measured difference in river flow between upstream and downstream reach boundaries; QTributaries is sum of flows provided by lower-order tributaries to the reach of the main channel; QSources is sum of other water flows added to the reach (e.g., industrial out-falls, precipitation, run-off etc.) and QSinksis sum of abstraction from the reach by other sources (e.g., water diversions, evaporation, etc.).

Accurate determination of QRiver is critical to successfully quantifying net groundwater con-tribution to the reach. Two conditions must be satisfied to be able to meaningfully determine QRiver as described previously: first, flow within the reach must be steady (or sufficiently steady) during the entire period between upstream and downstream flow measurement of river flow; and second, the magnitude of net groundwater flux must be significantly larger than the uncer-tainty associated with its calculation (Kalbus et al. 2006). A further condition for allowing val-

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id comparisons between reaches or river-wide evaluations is that time for which the river must remain under steady flow conditions is extend-ed to cover the entire measurement period for all reaches.

Minimizing the uncertainty associated with dif-ferential river flow measurements wherever possible was critical to detecting lowest possible groundwater contribution to the river. Appropri-ate selection of river flow measurement sites was critical for reducing the error and uncertain-ty associated with any flow measurement (Tur-nipseed and Saurer 2010). Measurement loca-tions were selected carefully following standard hydrometric guidance (e.g., WSC 1999a) and chosen such that they had a reasonably straight channel with parallel stream lines and uniform flow; a stable stream bed free of obstructions (e.g., large rocks and weeds that could create eddies), slack water, and/or turbulence; and a symmetrical channel geometry that was para-bolic or trapezoidal in shape, did not contain any abrupt changes in channel slope, and was of sufficient depth that areas unable to be gauged were avoided or minimized.

To facilitate high-quality groundwater flux mea-surements, the river was monitored continuous-ly for temporal changes in flow conditions. River flow measurements collected during periods of unsteady flow were rejected and were subse-quently repeated. To minimize the possibility of fluctuating flow conditions, river flow measure-ments were conducted during the late-summer and early fall when annual river low-flow/base-flow conditions typically occur. Additionally, field campaigns were scheduled (to the extent possi-ble) to avoid periods during or shortly after sig-nificant precipitation and were instead planned for times when little precipitation was forecast. River flow conditions were monitored along the river using temporary stage recording stations at each flow gauging location. Stage recording stations consisted of a pressure transducer (col-lected pressure and water temperature data at 5 min intervals) installed in small stilling wells attached to the angle iron and driven into the stream bed. Staff gauge plates were also at-tached to angle iron so that manual staff-gauge readings could be used to verify the pressure transducer data. These stations were estab-lished several days prior to commencing the dif-ferential flow measurements and remained until end of the field season.

River flow measurements were made using an Acoustic Doppler Current Profiler (ADCP; Stre-amPro by Teledyne RD Instruments). Sever-al recent studies have illustrated the potential of using ADCP flow measurements to quantify seepage losses in irrigation canals and ground-water infiltration/discharge in rivers (Hinkle et al. 2001; Ely et al. 2008; Kinzli et al. 2010, 2013; Williams 2011; Martin and Gates 2014). However, few studies have used ADCP flow measurements to attempt to quantify ground-water interactions (contributions and losses) and the associated uncertainty in smaller natu-ral streams (e.g., <5 m3/s) where the ability to detect direct groundwater flux at levels <5 % of stream flow was needed.

Although attempts were made to minimize the uncertainty and error associated with each measurement by carefully selecting measure-ment locations and following accepted mea-surement procedures, it was anticipated that measurement variability and uncertainty would be similar in magnitude to the groundwater dis-charge being quantified. To eliminate potential instrument bias, the same ADCP and operator were used for all measurements. A temporary bank-operated cable way was used to control the tethered ADCP, which allowed for more uni-form movement of the instrument and more consistent edge measurements; reducing vari-ability in measured flows (Rehmel 2006; Kinz-li 2010, 2013). Accepted ADCP measurement procedures as documented by the USGS (e.g., Mueller and Wagner 2009) and the Water Sur-vey of Canada (Environment Canada 2013) were followed for all measurements.

Under-ice flow measurements were performed using a SonTek FlowTracker and followed the traditional velocity-area flow approach. Mea-surements were collected at drilled holes spaced in the ice creating 20-30 panels for river flow calculations. Panel areas were then multiplied by measured velocities to yield panel flows, and panel flows were summed to yield total stream flow (WSC 1999b, 2015). The setting (e.g., un-der ice with reduced flows) and approach re-quired for obtaining the under-ice flow mea-surement produced flow estimates that contain much greater uncertainty (e.g., fewer replicates possible at each station because of setup/oper-ation time, entire cross section not accessible during ice-on conditions, etc.) than the mov-

8

ing-boat ADCP measurements collected at the same locations during open-water periods.

Additional inputs and withdrawals to/from river reaches (i.e., QTributaries, QSources& QSinks) were also evaluated and quantified using stream gauging (i.e.,using a Marsh McBirney flow meter and the velocity-area approach) or direct volu-metric measurements, where possible, to give a full accounting of water balance. By selecting measurement periods during low-flow periods without significant precipitation, over-land run-off and direct precipitation onto the river were assumed to provide no contribution to river flow. Provincial regulatory agencies were con-tacted regarding water diversion on the rivers selected for detailed investigations. There were no known water extraction or disposal licenses for these tributaries. Stream evaporation was measured directly using floating evaporation pans (Maheu et al. 2013), deployed at select stage recording stations and was found to be negligible over the measurement period. The contribution of flow from lower-order tributaries is expected to be the major source of additional flow (which may also provide a source of in-direct groundwater (tributary groundwater)) to the rivers. Lower-order tributaries were inven-toried and their flows measured where possible (e.g. >0.001 m3/s) using appropriate methods (e.g., stream gauging for larger flows and volu-metric for smaller flows). Lower-order tributar-ies were inventoried by first identifying features on existing 1:50,000 National Topographic Se-ries (GOC 2015a) maps and field verifying their status either by boat or helicopter.

Other Field Methods

Aerial infrared thermography was used to screen both banks of rivers for tributaries and to iden-tify potential areas of groundwater seepage. Tributaries identified using this technique were cross-referenced with the NTS-identified tribu-taries to further confirm their presence and to identify additional features (potential tributaries or channels from local groundwater discharge) that may have been missed by the 1:50000 mapping. Thermal signatures were also used to select tributaries that may be fed largely by groundwater based on cold observed water temperatures compared to other surface water features. Additional features identified by infra-red screening were also field verified to gain a complete inventory of flows to the river.

Surface water samples for chemical and stable isotope analysis were collected at each location and time that flow measurements were collect-ed on the main channel. Similarly, samples were collected during field verification of all tributar-ies with measurable flows. Selected features identified through infrared screening and sus-pected of being groundwater seeps were also sampled. In all cases, the same isotopic, geo-chemical and physical parameters used in the initial river screenings were collected for com-parative purposes and potential use in mass/isotopic balance calculations.

Statistical Approaches Applied to Flow Data

Determining groundwater flux and associated uncertainty for each reach examined required that measured river flow data have certain sta-tistical characteristics. It was expected that flow measurements performed during steady flow conditions with the same instrument and oper-ator would have only random error associated with measurements and therefore follow a nor-mal distribution. Based on this assumption, the two-sample Student’s t-test (Minitab 2010) was selected as the default method to compare the means of the upstream and downstream bound-ary and determine if a statistically significant difference existed (i.e., a net groundwater gain/loss). Prior to calculating groundwater flux for a reach, distribution of individual measured flows, collected at each of the sections bounding the river reach, was tested for normality using the Anderson-Darling test (Minitab 2010). Addition-ally, measured flow and automated stage data collected over the measurement interval were tested for the presence of a trend with respect to time. The absence of a statistically or practi-cally significant (i.e., statistically significant but within the uncertainty of the electronic field in-strumentation) trend in these data was inter-preted as an indication that sufficiently steady flow conditions existed during the measurement interval. If both normality and trend tests were satisfied then the t-test was performed and con-fidence intervals applied to the mean difference (i.e., groundwater flux for the reach) according to Helsel and Hirsch (2002).

ADCP Measurement Uncertainty

Considerable effort has been put into quanti-fying uncertainty of moving-boat ADCP mea-surements (González-Castro and Muste, 2007;

9

Oberg and Mueller 2007a, b; Czuba and Oberg 2008; Lee, et al. 2013; Le Coz et al. 2016). Unfortunately, “true” uncertainty is extreme-ly difficult to determine because “true” flow is seldom known in natural streams. Increased measurement (exposure) time is an important factor in reducing uncertainty associated with stream flow measurements. Oberg and Muel-ler (2007a) estimated uncertainties for ADCP measurements of 1.2–5 % depending on ex-posure time. Although studies have also made progress on developing a framework for apply-ing standardized uncertainty analysis methods to ADCP measurements (González-Castro and Muste 2007; Lee et al. 2013), these methods have yet to be applied at the operational lev-el. For application in this study, precision of the method was more critical than accuracy of the flow measurements. It was assumed that if data collected at each section could be obtained with a high-level of precision, then any systematic errors (i.e., a consistent bias) that contributed to uncertainty would be largely cancelled during the differencing calculation required to estimate groundwater discharge to the reach. The im-plicit assumption was that systematic error re-mains reasonably constant within a reach. This assumption was considered reasonable given that physical characteristics of the river at the upstream and downstream sections were sim-ilar in nature (e.g., geometry, bottom charac-teristics, etc.) and because the instrument and operator for all measurements were constant.

2.4 Results and Discussion

Four rivers were examined between summer 2012 and winter 2015 for evidence of ground-water interaction (Table 1).

Water Balance Methods

In 2013 methods were tested for their ability to quantify or constrain groundwater discharge into rivers at the reach scale. ADCP operator and equipment availability allowed only two riv-ers to be examined during this study year. Al-though the Firebag River was screened in 2012, and was considered to have one of the greatest groundwater influences (RAMP 2013; Gibson et al. 2016), it was not selected because of the in-creased transit time between Fort McMurray and the river relative to other rivers. The Steepbank and Ells were selected for preliminary testing of

the differential flow method. The rivers provided a range of flows to test and, being on opposite sides of the Athabasca River, different physical settings. It was assumed based on a similar set-ting and river characteristics that the MacKay and Ells rivers were likely more similar in na-ture than the Steepbank. Further, the Ells was originally preferred over the MacKay because of limited JOSM efforts occurring on the MacKay River.

The differential flow gauging method proved to be successful on both rivers; however, lower flows on the Steepbank required longer reaches to establish statistically significant differences. The experience and observations from the Ells and Steepbank were used to add a statistical element to the study design for year three. This helped determine the operational requirements needed to obtain the necessary precision from the ADCP measurements. Based on results from pilot tests conducted in year two, it was de-termined that approximately 30-36 individual (i.e., 15-18 reciprocal pairs) river flow transects could be completed using the ADCP method at each river section in approximately three hours. This included time from set-up to completion, including transit time to the next downstream section. An analysis of the preliminary data in-dicated that flow measurements were generally normally distributed and that means and vari-ances were not correlated. A statistical pow-er analysis based on these measurements in-dicated that 30-36 transects should provide a statistically significant measurement resolution of 3-6 % of observed typical stream flow (with asymptotic behaviour being observed between uncertainty levels of 2-4 % at approximately 60 transects).

The final year of study (2014/2015) involved a full-scale demonstration and evaluation of groundwater-surface water interactions on the MacKay River. The MacKay River was selected over the Ells for this evaluation based on its relatively higher average flows, more geologi-cal and hydrogeological information available and greater extent of proposed future develop-ment in the watershed. The section used in the evaluation extended from the confluence of the Dunkirk River downstream to the confluence of the Dover River, both major tributaries of the MacKay (Fig. 2). The selected study section was limited to this interval to avoid the confounding influence of Dunkirk and Dover rivers.

10

Table 1. Overview of groundwater-surface water activities.

11

A first attempt at characterizing the direct groundwater interactions to the MacKay River was made in August 2014. Unfortunately, riv-er conditions were not steady enough to obtain reliable results for differential flow estimates at all sections. A second successful attempt was completed in September 2014. An under-ice as-sessment was made in March 2015 but it was limited to the interval between Stations 4 and 6 because of inclement weather and resulting flight restrictions during field activities. Gener-al stage conditions of the MacKay River during these measurement campaigns were obtained using historical data from the Government of Canada hydrometric station 07DB001 (GOC 2015b) (Fig. 3) and a full inventory of the 44 lower-order tributaries contributing to the study section was produced (Fig. 4).

Several intervals without statistically significant changes in river flow are observed, suggesting that very little direct groundwater interaction occurs along these reaches (Figs. 5, 6, 7). For

the reaches where gains are observed, the in-crease in flow can be attributed to contributions from lower-order tributaries except for the 5 km reach between Section 5 and Section 6 and pos-sibly the 38 km reach between Section 6 and Section 9. Direct groundwater contribution to the reach between Section 5 and Section 6 was estimated to be between 0.032 m3/s and 0.147 m3/s with no lower-order tributary contribu-tions observed. This represents approximately 1-6 % of the total measured river flow observed at Section 12 (i.e., just upstream of the Dover River confluence). There is greater uncertain-ty regarding the direct groundwater contribu-tion between Section 6 and Section 9 because of uncertainty in the flow measurements for lower-order tributaries contributing to this riv-er section (for which reliable confidence inter-vals could not be established with current data). However, it appears that contribution from lower order tributaries between Section 6 and Section 9 cannot account for a significant portion of to-tal flow gain within the interval. After correcting

Figure 2. MacKay River study reach (i.e., from confluence of the Dunkirk River downstream to the confluence of the Dover River) and locations of the 12 river cross-sections used for ADCP-based flow and stage measurements.

12

Figure 3. Historical stage of the MacK-ay River at Government of Canada hydrometric station 07DB001 (August 2014 to August 2015) showing the general river conditions during the (a) August 2014, September 2014 and March 2015 flow measurement cam-paigns; (b) August 2014, September 2014 flow measurement campaigns; and (c) the timing of the flow measure-ments at various river cross sections during September 2014.

13

Figure 4. Locations of the 44 lower-order tributaries contributing surface water to the MacKay River along the 125-km study section.

Figure 5. Mean river flows and 95 % confidence intervals from the September 2014 and March 2015 measurement campaign.

14

Figure 6. River interval gains in flows and associated 95 % confidence intervals for the Mackay River and the contribution of lower-order tributaries to the interval flow gains for the September 2014 measurement campaign. (Note: Interval Flow Gain plotted at mid-point of interval).

Figure 7. River interval gains in flows and associated 95 % confidence intervals for the Mackay River and the contribution of lower-order tributaries to the interval flow gains for the March 2015 measurement campaign. (Note: Interval Flow Gain plotted at mid-point of interval; unlabelled lines representing intermediate sections not measured in March 2015 retained for reference).

15

for the tributary contributions, the net ground-water discharge between Section 6 and Section 9 is estimated to be between 0.013 m3/s and 0.115 m3/s (i.e., respectively, 0.5 % and 4 % of total river flow measured at Section 12). For comparison, total contribution of all lower-or-der tributaries to the 125-km river section was measured to be approximately 0.890 m3/s, rep-resenting 33 % of total measured flow observed at Section 12. Note that the majority (i.e. ap-proximately 57 % to 67 %) of the total flow mea-sured at Section 12 enters the study area at the upstream boundary (i.e. Section 1; downstream of the confluence with the Dunkirk River). How-ever, during under-ice periods it appears the relative importance of groundwater and tribu-tary contributions reverses. Observations made in March 2015 estimate the groundwater con-tribution between Section 4 and Section 6 to be between 0.021 m3/s and 0.085 m3/s (i.e., simi-lar to that observed in the same interval in Sep-tember 2014) and a total tributary contribution of approximately 0.062 m3/s. Only two actively flowing tributaries (located between Section 2 and Section 6) were identified on the MacKay River between the confluences of the Dunkirk and Dover rivers in March 2015. Direct compar-isons to September 2014 data are not possible because of the reduced data available for March 2015, particularly the absence of groundwater discharge information between Section 6 and Section 9 and total river flow at the downstream boundary (i.e., Section 12). However, assuming groundwater input remained relatively constant between September 2014 and March 2015 (as suggested by data obtained between Section 2 and Section 6) and that all active lower order tributaries were measured in March 2015, to-tal river flow is estimated to be 0.58 m3/s at Section 12 in March 2015 (i.e., the sum of the river flow at Section 6 in March 2015 and the estimated groundwater discharge between Sec-tion 6 and 9 from September 2014). Based on this approximation of river flow at Section 12, total direct groundwater discharge and tributary contribution to total river flow at Section 12 in March 2015 are estimated to be 6-35 % and 11 %, respectively. It appears that the direct groundwater discharge is significant for mainte-nance of riverine under-ice flow. What remains unknown is the full contribution of groundwater to the main channel. The indirect groundwater discharge contributed to the main channel via lower order tributaries (i.e., tributary groundwa-

ter) and proportion of groundwater at upstream boundary was not quantified in this study.

Comparisons of the results of this study to ex-isting studies are not ideal because of differ-ing study areas and the aggregating of direct and indirect groundwater contributions in many existing studies. Gibson et al. (2016) estimate that the total groundwater contribution (i.e., direct and indirect) to river flow at the Water Survey Station 07DB001 (GOC 2016) is 14 % and 45% for summer/fall and winter (i.e., un-der ice) periods, respectively (note that station 07DB001 is downstream of Section 12 and in-cludes the contribution from the Dover River, Dunkirk River and sections of the MacKay River upstream of the Dunkirk confluence). Fall and winter estimates from this current study sug-gest that 4-29 % (fall) and at least 16-65 % (under ice) of river flow gains between Section 2 and Section 12 (note that no contributing trib-utaries downstream of Section 6 were observed in March 2015) was from direct groundwater discharge (indirect contribution not estimated) to the MacKay River. These estimates are at least consistent with the findings of Gibson et al. (2016) and potentially may give some in-sight into the relative importance of direct ver-sus indirect discharge (e.g., groundwater con-tributed via lower-order tributaries). Both this study and Gibson et al. (2016) also estimate an approximately 3-fold increase in the propor-tion of groundwater contributing to the MacKay River flows in winter compared to the contribu-tion in the fall. The apparent consistency of the studies at this stage is encouraging as they use different techniques/approaches to investigate groundwater contributions at different scales: Gibson et al. (2016) - watershed scale; this study - detailed reach-scale.

Field observations of groundwater discharge ob-tained from this study were also of the same order of magnitude as estimates from ground-water modelling performed to support the EIAs for various proposed oil sands developments (CEMA 2014). Results from these simulations estimated discharge to the MacKay River to range between 0.01-0.055 m3/s for existing con-ditions (i.e., pre-development). No direct field measurements of groundwater discharge were available for model calibration and validation. Further groundwater modelling (CEMA 2014, 2015) has suggested that a potential impact of

16

development on the MacKay River may be local reversal of groundwater flow (i.e., river water becoming groundwater). Potential groundwater reversals from the river are a significant ecolog-ical concern as groundwater discharge is often required for maintenance of critical aquatic hab-itat and thermal refugia for fish (e.g., Kurylyk et al. 2014). Based on field observations made during this study, it appears that groundwater discharged to the 5-km reach identified (be-tween Section 5 and Section 6), and possibly the 38-km reach (or portion of) between Sec-tion 6 and Section 9, may be critical to main-taining flow for the entire river during ice cover periods. Identifying similar critical reaches on other tributaries is required to properly evalu-ate the impacts of development on river eco-systems and to understand which areas require more careful monitoring.

Although the approach developed in this study to assess groundwater-surface water inter-actions was demonstrated to give a relatively rapid assessment of an entire river and to pro-vide estimates of groundwater discharge at the reach-scale, several limitations were noted. The ability to resolve groundwater discharge with-in a reach/river depends highly on the relative magnitudes of groundwater input and river flow, and the stability of river flow. For example, the approach in its current form would not be suit-able for periods characterized by rapid chang-es in river flow (e.g., freshet). Refinement of a reach for determining groundwater input is also limited by ADCP resolution and currently appears to be practically limited to approxi-mately 5 km. At this stage in method develop-ment, approach applicability and limits have not been fully explored. However, the method was principally tested on the MacKay River, which other studies suggest has the lowest ground-water contribution of the four tributaries exam-ined (i.e., Ells, Firebag, MacKay and Steepbank rivers), suggesting that the method might be even more robust on rivers with higher direct groundwater fluxes. Uncertainty associated with the groundwater discharge estimates obtained using the water balance approach limits the ac-curacy of mass loadings from groundwater but does provide useful constraints that were not previously available.

2.5 Summary and Conclusions

For the MacKay River section studied, it was estimated that direct discharge of groundwa-ter provides a small contribution (i.e., approxi-mately 2-10 % of fall low flow) to total river flow during open water periods but perhaps 35 % for under-ice flow. The full ecological importance of this remains unclear but it may be important in maintaining thermal regimes favourable to biota and preservation of aquatic habitat during under ice periods). Furthermore, results of this assessment for the MacKay River provide a reference condition for groundwater discharge for potential future comparisons if periodic as-sessments are deemed appropriate to assess progressive impacts of development on ground-water discharge to the river.

The approach established in this study demon-strates its utility in identifying locations and regions of groundwater input and obtaining estimates/constraints of groundwater discharge at the reach scale. To date, there have been no other studies in the region to provide infor-mation on the nature of groundwater-surface water interactions at this small spatial scale. The approach provides a relatively rapid assess-ment of the role and importance of groundwater discharge to a river by providing information on where, and where not, aquatic habitat and sur-face water quality may be most vulnerable to changes in groundwater discharge and quality. This information in turn can be used to design and inform surface water and aquatic health monitoring programs so that groundwater influ-ences may be integrated into the interpretations of monitoring data and programs designed to properly attribute the source of these changes.

17

3.1 Background

As discussed in the Introduction, there is a po-tential concern for groundwater affected by OSPW (oil sands process water) from tailings ponds to reach nearby rivers and impair aquatic ecosystems (RSC 2010). Surface mining of oil sands requires a caustic, hot-water extraction for isolation of bitumen (FTFC 1995), which re-sults in production of tailings: a waste product consisting of an alkaline and saline suspension of sand, silt, clay, residual bitumen and naph-tha. The aqueous portion of the waste, OSPW, contains a complex mixture of neutral and polar organic compounds, including naphthenic ac-ids (NAs). Given restrictions on tailings release to local rivers, companies have stored tailings on site in large tailings containments (ponds). These ponds are typically 5-15 km2. In gener-al, they are constructed of hydraulically em-placed coarse tailings (largely sand) that form a containment dyke to hold in subsequently-de-posited tailings (Fig. 8). Within the dykes are collection systems (Fig. 9) designed to capture internal drainage from the constructed dyke (of-ten called ‘‘construction water’’ and which may contain OSPW), and leakage of OSPW from the pond itself (or “tailings water), while also pro-viding geotechnical stability. Ditches outside dykes may also be used to capture OSPW-af-fected groundwater migrating from below the dyke. Captured water is subsequently returned to tailings ponds. Development of low hydraulic conductivity sediment layers at the bottom of these ponds from settling of fine tailings may help restrict leakage (Ferguson et al. 2009).

Water used for bitumen extraction is obtained from the Athabasca River and through recycling of OSPW; this then results in elevated levels of naphthenic acids (NA) and inorganic ions (Na, Cl, SO4 and HCO3) in OSPW relative to the lo-cal rivers (Allen 2008). Unrecovered bitumen in OSPW is composed mainly of saturated and polar hydrocarbons, with a minor fraction be-ing alkylated PAHs. OSPW also contains as-phaltenes, benzene, phenols, cresols, humic and fulvic acids, phthalates, toluene and ele-vated concentrations of metals (including lead, mercury, arsenic, nickel, vanadium, chromium and selenium) (Allen 2008). It is also possible that tailings ponds have received other waste water from industry activities.

Freshly produced OSPW is acutely toxic to aquatic organisms, with NA in their dissociated ionic form thought to be primarily responsible (MacKinnon and Boerger 1986). Acute toxicity declines over time, likely due to a decrease in the proportion of lower molecular weight NA. The natural biodegradation of NA in OSPW is slow and yields an increasing proportion of mono-, di-, and tri-hydroxylated NA (Brown and Ulrich 2015). Some enriched metals also undoubtedly play a role in the acute and chronic toxicity of OSPW, with several found above water quality guidelines for various aquatic vertebrate and invertebrate species.

Several field-based studies have shown or sug-gested OSPW-affected groundwater flowing from various tailings ponds or their dykes. This includes investigation of Mildred Lake tailings

Limestone

Clay Core

Sand Tailings

Internal FilterDrain

OverburdenDyke

River

Plant AccessRoad Dyke

Fine TailingsValley Wall

SandSilt and ClaySnye

W E

Figure 8. Cross-section of study tailings pond (dyke and tailing deposition; Pond 1). Modified after Hunter (2001).

3. Sub-Theme B: Potential Tailings Pond Leakage

18

Figure 9. Plan view of study tailings pond (Pond 1) showing drainage collection system. Modified after Hunter (2001).

pond (MacKinnon et al. 2005) and mapping of an OSPW plume extending approximately 500 m from it towards the Athabasca River (Oiffer et al. 2009). Capture of OSPW-affected groundwa-ter into containment ditches outside the dyke of the Muskeg River Mine tailings pond was inves-tigated by Yasuda et al. (2010). Numerical mod-elling of Pond 1 suggested that leakage from the pond and dyke system to underlying aquifer materials was possible (Ferguson et al. 2009). Total leakage was estimated for 1999 conditions at <65 L/s, which is about 0.1 % of the lowest daily Athabasca River flow recorded, with direct loss from the pond bottom estimated at about 2.0 L/s. Possible indications of OSPW-affected groundwater from Pond 1 reaching shallow sed-iments of the Athabasca River have been re-ported (Baker 1999, Hunter 2001, Ferguson et al. 2009), based largely on naphthenic acid and Na concentrations and Na–Cl ratios. Parameters

that have been used or proposed as indicators for OSPW-affected groundwater in other studies include Na, Na–Cl ratio, NA by Baker (1999); B, NH4, NA, by MacKinnon et al. (2005); SO4, Cl, NH4 by Allen (2008); HCO3, Na, Cl, SO4, NA, B by Oiffer et al. (2009); and NA, Na, Cl by Yasuda et al. (2010). However, these constitu-ents are also found in natural groundwaters in the area, particularly those affected by natu-ral oil sands of the McMurray Formation (e.g., Baker 1999).

Given the toxicity of OSPW noted above, dis-charge of groundwater affected by OSPW from tailings ponds to nearby rivers or wetlands has the potential to impair water quality and the health of aquatic ecosystems. Develop-ment of monitoring programs for surface water quality and biota health will thus benefit from knowledge of the current status of discharging groundwater near tailings ponds and from tools to distinguish OSPW-affected groundwater from natural groundwater.

3.2 Objectives

From the implementation stage of JOSM, the goal of sub-theme B was to address potential leakage of groundwater affected by OSPW from tailings ponds to nearby surface waters and any resulting risk posed to aquatic organisms. Suncor’s Pond 1, being the oldest tailings pond (now reclaimed) and the one closest to a major river, and with past suggestions of such leakage (described above), was chosen as the primary focus of this work. Objectives of this study are to address:

• Whether discharging groundwater adja- cent to Pond 1 is currently posing an elevated risk (i.e. toxicological) to aquatic life (considering common groundwater contaminants);

• How to differentiate groundwater affect- ed by OSPW (from tailings ponds) from other groundwaters in the area of oil sands development (including natural groundwater from the oil sands-bearing McMurray formation).

• If groundwater affected by OSPW from Pond 1 is reaching the Athabasca River (This objective was dependent on the methodological outcomes of objective 2).

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For objective 1, OSPW and OSPW-affected groundwater associated with Syncrude’s Mil-dred Lake tailings pond were also included with those of Pond 1. Note also that all groundwater sampling was performed during the open-water season, so the study findings may not be ap-plicable to conditions during winter when river levels are low.

3.3 Methods

This study involved collection of groundwater samples from shallow sediments along rivers both adjacent to and away from tailings ponds, and from wells along the Mildred Lake ground-water plume, and as part of on-site collection systems of two different tailings ponds. River water samples and samples of OSPW from sev-eral tailings ponds were also collected for com-parison purposes. These samples underwent chemical analyzes using a wide range of com-mon and newly-developed analytical techniques (Table 2).

For Part 1, approximately 180 shallow riparian groundwater samples were distributed uneven-ly (due to access issues and variable ability to obtain shallow groundwater) across 11 different

zones (geographical areas; Fig. 10) in the re-gion of the tailings pond of primary focus in this study (i.e., Pond 1). Four zones were adjacent to Pond 1 along the Athabasca River. Several other zones were also along the Athabasca Riv-er, while samples collected along the Muskeg, Steepbank and Ells rivers comprised three in-dividual zones (Fig. 10). Water quality, based on routine geochemistry, of these samples, and river and OSPW samples, was compared to ad-dress objectives 1 and 3.

For Part 2, novel high-resolution analytical tech-niques were applied to a smaller set of ground-water samples (Fig. 11; as well as two OSPW samples). These included shallow riparian samples from the data set collected for Part 1 (including locations beside the study pond and away from any tailings pond, and targeting samples with evidence of elevated NA). Sev-eral of these samples, plus an additional seep sample, were collected directly from natural oil sands deposits of the McMurray formation. Other groundwater samples included here were collected from on-site wells around Pond 1 or the Mildred Lake tailings pond. Comparisons of these sample results were directed toward addressing objectives 2 and 3.

Table 2. Description of the various sets of groundwater and other types of water sam-ples collected.

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Study Pond

PondPond

NENW

SW

EP

Pond

0 1 2 3 km

N

Fort McMurray

Athabasca R

iver

Ells River (EL)

Oil Sands Development

Municipal

Undeveloped

Legend

(circa 2012)

0 5 10 15 20 km

N

a)

b)

b)

c)

Pond

StudyPond

Pond

PA

PB

PC

PD

Athabasca River

0 0.5 1 km

N

c)

Pond

Figure 10. Areas of groundwater sampling within the oil sands area for Part 1: a) zones EL, MR, SB, consist-ing of tributaries of the Athabasca River, b) inset showing zones NW, NE, EP, SW along the Athabasca River, and c) inset showing the 4 pond-site zones (PA, PB, PC, PD) beside the study tailings pond. Reproduced from Roy et al. (2016), with permission from John Wiley and Sons Publishers.

Part 3 focused on the same six shallow ground-water sites as Part 2 (with three samples each spaced 20 m apart; termed priority samples; Table 2), with 13 additional samples away from any tailings pond. Part 4 involved collection of groundwater samples from established wells along the known OSPW-affected groundwater plume from Mildred Lake tailings pond, which was well characterized using routine geochem-cial and NA profiles (Oiffer et al. 2009). These studies were designed to further test the ana-lytical suite developed in Part 2 for its ability to distinguish OSPW-affected groundwater from other groundwater in the area. Both include a few additional analyzes (perfluorinated com-pounds and artificial sweeteners) and greater sample volumes to allow for improved detection limits. Part 3 expands the testing to a broad-er range of background groundwaters in the region, including groundwater sampled direct-ly from natural oil sands deposits in several

different areas. Part 4 challenges the analytical suite at a different tailings pond (i.e., Mildred Lake) and across a temporal gradient in OSPW composition.

The groundwater sampling method is described by Frank et al. (2014) and Roy et al. (2016). Briefly, shallow groundwater samples were col-lected at depths of 30-120 cm below the stream bed along the edge (banks or connected sand-bars) of the Athabasca River and associated tributaries (Ells River, Muskeg River, Steepbank rivers). Samples were obtained with a peri-staltic pump using a stainless steel drive-point system (Roy and Bickerton 2010). Hand-held meters were used to measure water properties (pH, electrical conductivity (EC), dissolved oxy-gen (DO), temperature) on site. If these prop-erties were similar to those of the above river water, which is a possible indication of shallow hyporheic flow or short-circuiting along the rod,

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the sampler was driven deeper. In some cases, the penetration depth was limited by competent bedrock (likely upper Devonian carbonates in most cases, which underlies the McMurray for-mation (King and Yetter 2011)). Groundwater samples from wells were collected using a peri-staltic pump often following purging of the well by the staff of the oil sands operators (i.e., the well custodians). OSPW and river water were collected as grab samples. Sample preservation and storage details are provided by Roy et al. (2016).

Complete descriptions for those analytical pro-cedures used for Parts 1 and 2 (and applied also to Parts 3 and 4) of this study (Table 2) are provided by Frank et al. (2014) and Roy et al. (2016). A description of the additional analy-ses of Parts 3 and 4, i.e., artificial sweeteners and perfluorinated compounds, is provided by

Van Stempvoort et al. (2011) and de Silva et al. (2011), respectively.

Several statistical approaches were applied to assessment of the field data for Parts 1 and 2. These include Mood’s median test to compare water quality parameters between ponds-site and non-pond data sets, confidence interval box plots to assess any influence of sampling depth, as well as principal component analysis (PCA) and non-metric multidimensional scaling (NMDS) for multivariate assessment of the dif-ferent zones based on geochemical parameters. Descriptions and explanations of these tests are provided by Roy et al. (2016).

3.4 Results and Discussion

This study consisted of four parts, each of which involved different sets of groundwater samples

Figure 11. Map depicting sampling locations of OSPW, near-field and far-field locations prioritized for detailed profiling, as a component of Part 2. Inset depicts close-up of area illustrating locations of Site B near-field drive-points, interceptor and monitoring wells. Reprinted with permission from Frank et al. (2014) Profiling oil sands mixtures from industrial developments and natural groundwaters for source identification. Environ Sci Technol 48: 2660-2670. Copyright (2014) American Chemical Society.

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Figure 12. Box-whisker plots showing the quartile range comparison of the 20 guideline compound concentrations in shallow groundwater between non-pond (-np; those away from any tailings ponds) versus pond-site (-ps; those adjacent to the tailings pond of interest) samples. Dashed line indicates the aquatic life guideline value or (two lines) range (CCME 2007). Asterisk denotes data set is significantly higher (p< 0.05; Mood’s Median Test). Note the differences in scales and breaks of the y-axes.

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collected from along the Athabasca River or its major tributaries, or from on-site industry wells in the area of oil sands mining. The majority of these samples were associated with Suncor’s Pond 1 tailings pond, though some were associ-ated with Syncrude’s Mildred Lake tailings pond, and others targeted background groundwater (Table 2).

Objective (1): Potential Risk to Aquatic Life

Part 1 of this study consisted of a concentra-tion comparison of geochemical constituents (or proxy markers), including trace metals or metalloids, major ions, and synchronous fluorescence spectroscopy profiles of aromatic naphthenic acids (SFS-ANA), in shallow ground-water from riparian areas both adjacent to the Pond 1 tailings pond (i.e., pond-site samples), and away from any tailings pond (i.e., non-pond samples) (Roy et al. 2016). The underlying hy-pothesis is that a higher risk profile for these parameters for discharging groundwater adja-cent to Pond 1 would likely be associated with OSPW contamination. For both data sets (pond-site, non-pond; 125 samples total), 11 of the 20 guideline compounds had at least one sam-ple with concentrations above their aquatic life water quality guideline value; with 10 of these compounds shared by both sets. In comparing the concentrations of guideline compounds (Fig. 12) for these two groups, the majority showed no significant difference (Mood’s median test), with only F, Mo, Ni, Se, and U concentrations significantly greater for the pond-site sample set and Cr and Fe significantly greater for non-pond locations. This suggests that for the tested constituents and at the broad scale considered here, shallow groundwater conditions adjacent to the study pond currently pose no greater tox-icity risk to benthic and other aquatic life than nearby reference sites.

We note that there are several factors that may influence the above findings. First, there is potential that these shallow groundwater sam-ples have been influenced to some degree by river water infiltration (e.g., hyporheic flow, bank storage). However, an evaluation considering river hydrographs (with bank storage associated with sharply rising limbs and bank storage re-turn occurring during subsequent falling limbs) and comparing river water and groundwater chemistry (most strongly differing in dissolved oxygen, electrical conductivity, and major ions)

suggests there was no substantial influence of river water infiltration for the vast majority of samples (see Supporting Information of Roy et al. (2016) for a detailed evaluation). Second, the potential effects from deeper groundwater flow paths discharging to the middle of the river, rather than the shallow groundwater discharge along the banks, are not considered here.

Objective (2): Diagnostic Characteristics of OSPW

Parts 2, 3 and 4 of the study are directed pre-dominantly toward this objective. Part 2 results are summarized here, with complete details reported in a scientific manuscript by Frank et al. (2014). Data sets for Parts 3 and 4 of the study are still awaiting full completion of ana-lyzes and will not be discussed in detail here. Results indicate that common geochemical pa-rameters (with relatively simple and routine an-alyzes; Level 1), including NA concentration or SFS-ANA as a proxy, cannot be used in isola-tion or in combination as a universal indicator of OSPW-affected groundwater. This is because these parameters were unable to distinguish OSPW from various discharging groundwaters collected away from tailings ponds but within the area of active oil sands mining, including samples containing bitumen-derived AEOs (acid extractable organics) from McMurray Formation sediments. However, some of these parameters show promise as screening level indicators of OSPW-affected groundwater due to similarities with OSPW chemistry; these are NA or SFS-ANA (as proxy), F, Mo, Se, and Na–Cl ratio, and pos-sibly Na, B, and general water chemistry type (e.g., alkaline). In future, screening with these parameters could tag select groundwater sam-ples from larger data sets for more thorough and definitive analyzes.

A restricted set of OSPW and groundwater sam-ples (Part 2) were subjected to Level-2 profiling analyzes: i.e., electrospray ionization high reso-lution mass spectrometry (ESI-HRMS) and com-prehensive multidimensional gas chromatog-raphy time-of-flight mass spectrometry (GC × GC-TOF/MS). Differentiation of natural ground-water (even those with bitumen-derived AEOs) from OSPW sources was apparent through mea-surements of O2:O4 ion class ratios (ESI-HRMS) and diagnostic ions for two families (A and B) of suspected monoaromatic acids (GC × GC-TOF/MS) (see Fig. 13 (Fig. 5 Frank et al. 2014) for a comparison of these analyzes). The resem-

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Figure 14. Locations of groundwater samples collected in zones PA and PB; those in red are likely OSPW- affected (Part 2; Frank et al. (2014)); those in yellow are the suspect set identified in Part 1 (Roy et al. 2016); those in green are likely non-affected by OSPW.

Figure 13. GCxGC-TOF/MS ion chromatograms for select samples from OSPW, Far-field (Drive point 1) and Near-field (Drive-point 4) sites. Shown are the mono-aromatic m/z 145 (Family A) and m/z 237 and 310 (Family B) ions (see Frank et al. (2014) for exact retention times). Reprinted with permission from Frank et al. (2014) Profiling oil sands mixtures from industrial developments and natural groundwaters for source identi-fication. Environ Sci Technol 48: 2660-2670. Copyright (2014) American Chemical Society.

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blance between the AEO profiles from OSPW and from six groundwater samples adjacent to two tailings ponds, in particular two of these as-sociated with on-site tailings drainage collection systems, implies a common source. The pro-files provided by these methods, used in com-plement with the Level 1 analyzes, collectively suggest that differentiation of OSPW from nat-ural groundwater is possible. However, it is not yet known whether these methods will apply to other tailings ponds not investigated here, due to potential differences in oil sands sediments or in treatment processes, or variable effects of aging. These issues are being explored in re-lated Environment and Climate Change Canada research (e.g. Lengger et al. 2015; Frank et al. 2016).

Objective (3): Does OSPW discharge to the Athabasca River

A statistical comparison of simple geochemical parameters was made for Part 1 between two large data sets of shallow groundwater sam-ples: those collected adjacent to the study tail-ings pond (i.e., pond-site samples) and those collected away from any tailings pond (i.e., non-pond samples). The result was a high-degree of similarity between the two data sets, which sug-gests there is no increased toxicity risk beside the tailings pond at this time. This similarity in geochemistry might result from a lack in broad-scale input of OSPW-affected groundwater from Pond 1 to the Athabasca River. However, it could also be that subsurface transport to the river has been accompanied by contaminant attenu-ation or sufficient dilution to reduce concentra-tions to levels representative of the surrounding area. Without the option of a detailed on-site investigation, determining which case it is must rely on further chemical source attribution techniques.

Application of more advanced (Level 2) analyzes from Part 2 showed that the chemical profiles of two of the six shallow riparian groundwater samples more closely resembled those of OSPW than any of the far-field samples, particularly in the presence and distributions of the Family A and B acids. These two samples were taken at <1 m depth, from locations adjacent to Pond 1 in areas with measured upward groundwater flow (i.e., groundwater discharge to the river). While sample size was low, these results sug-

gest that OSPW-affected groundwater is reach-ing sediments of the Athabasca River adjacent to Pond 1. Preliminary findings from Part 3 sug-gest similar patterns for the original Level 2 an-alyzes, with the same two shallow groundwater sample locations still showing similar composi-tion to OSPW, in contrast to the expanded set of background samples.

The large data set of shallow groundwater sam-ples of Part 1 was then compared to the two OSPW samples and the two shallow groundwa-ter samples identified above as likely OSPW- affected. Assessment with PCA using multiple indicator parameters (SFS-ANA, F, Mo, Se, and Na–Cl ratio) identified a small subset of samples that had similarities to these four key samples. All samples from this subset were from loca-tions adjacent to Pond 1 (Fig. 14). This may be an indication that OSPW-affected groundwater reaches Athabasca River sediments at more lo-cations than determined with the high-res ana-lyzes (Part 2). Note that these additional loca-tions are not congregated in a single area and that groundwater samples that do not show signs of OSPW influence were collected from the adjoining areas. This suggests sporadic and sparse signs of leakage, rather than a broad-scale issue, which fits with the first set of find-ings from Part 1 described above.

3.5 Summary and Conclusions

The study results to date suggest that generally there is no broad-scale (i.e., covering 100s of m) increased risk posed to aquatic life from ground-water discharging adjacent to Pond 1 in com-parison to other nearby areas. However, there are indications that OSPW-affected groundwa-ter has reached Athabasca River sediments be-side Pond 1 at several locations. Whether these locations are experiencing localized ecological impairments has not been assessed and will be an important area of research for the future.

This work has also led to the development of a 2-tier suite of chemical analyzes toward screen-ing and then identifying OSPW contamination of groundwater. The screening step comprises sev-eral routine analyzes, building on key indicators suggested in published studies (e.g., NA, Na, Na:Cl ratio) with some additional ones (F, Mo), which may or may not apply to all other tailings ponds. Groundwater samples targeted by the screening process would then be subjected to

26

several advanced analyzes, which show promise for confirmation of OSPW-influence for two tail-ings ponds studied to date. However, variability in OSPW chemistry between tailings ponds or with changing extraction methods may chal-lenge application of this suite of analyzes. Im-provements and extended testing of this OSPW source attribution methodology is ongoing. This work is not a prescription for monitoring all tailings ponds for OSPW leakage to nearby rivers, given that very large numbers of sam-ples would be needed. Rather, this methodolo-gy (i.e., river-side sampling of shallow ground-water and application of this suite of analyzes) is better suited as an assessment tool for fol-low-up investigations of areas noted as poten-tially impaired, following monitoring of river wa-ter quality or ecological impacts. In these cases, the 2-tier set of analyzes could be applied to identify the presence and extent of OSPW con-tamination. In addition, the suite of 2-tier an-alyzes might also be applied to surface water samples (or perhaps even river biota) to identify substantial discharges of OSPW (via groundwa-ter or other means).

4. Theme Assessment

4.1 Integration with other Themes of the Water Component

Findings from this study provide context for sur-face water quality, water quantity and regional hydrology interpretations, and offer a founda-tional assessment of the relative importance of groundwater discharge to local rivers to guide and inform future activities with aquatic eco-system (e.g., fish, benthic community) health and surface water quality considerations. For instance, changes in chemical concentrations along the Mackay River can now be informed by the changing contribution of groundwater along its length determined in this study. Locations of groundwater discharge may also be considered for their role as thermal refugia for fish and oth-er aquatic species that may influence their sur-vival during hot, dry summers or over winters (by preventing freezing in river sediments).

In addition, groundwater samples have been collected and provided to several Environment and Climate Change Canada toxicologists for as-sessment of the influence of OSPW contamina-tion on toxicity to aquatic life and a comparison of this toxicity to what may result from natural groundwater components (especially McMur-ray Formation-sourced groundwater). Some of these results are presented in the other theme reports, while other work is ongoing.

4.2 Future Research Needs in Support of Monitoring

Several key research needs were identified and recommended based on the findings from the groundwater contributions to tributaries sub-theme A. Of particular importance is the need to:

• Perform complete groundwater-surface water assessment on remaining major tributaries in the active mining area (e.g., similar to that conducted on the MacKay River in this study); • Assess the ecological importance of groundwater discharge to the river (and other groundwater-dependent ecosystem such as wetlands) ecosystem in terms of its role in maintaining aquatic fish and benthos habitat during open water and ice-cover conditions (in conjunction with benthos and fish Themes);• Examine in more detail the increasing relative importance of groundwater to river flows during under-ice periods; and• Conduct an updated and comprehensive literature review on ADCP uncertainty and the implications for differential stream gauging techniques for low flow rivers.

Additional research and assessments that would be beneficial and may be required to support previous recommendations are to:

• Evaluate the full range (e.g., flow condi- tions, river geometry, etc.) of applicability of the methodology, identify limitations and develop necessary refinements where possible, including uncertainty analysis;• Investigate seasonal and annual variabil- ity of groundwater discharge to identified critical reaches with significant ground- water discharge;

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• Explore and quantify the contribution of indirect groundwater discharge to the main channel via lower-order tributaries, including seasonal changes and the role of intermittent streams and wetlands;• Assess the comparative nature of benthic communities in identified groundwater discharge areas in conjunction with the benthos theme; and• Conduct groundwater studies on ground water pathways associated with the iden- tified groundwater discharge locations to better evaluate their nature, vulnerabil- ity, etc. and effects on them (and the river to which they discharge) from exist- ing and proposed developments.

The immediate research needs associated with the findings of the potential tailings pond leak-age sub-theme are to:

• Assess whether locations identified as having groundwater affected by OSPW show observable negative effects on biota. This assessment would provide information on potential ecological effects of this possible route of contamination;• Further evaluate the developed 2-tier suite of analyzes for OSPW source attri- bution to determine how well it applies to other tailings ponds and evaluate if interferences from other anthropogenic sources (i.e., determine its general appli- cability and limitations) exist; and• Evaluate if the developed 2-tier suite of analyzes for OSPW source attribution can be applied to ecological receptors (e.g., fish bile).

4.3 Monitoring Recommendations

Research conducted under the groundwater theme was intended to provide foundational as-sessments to inform future monitoring activities and identify locations related to water quality, water quantity and ecological health. Groundwa-ter considerations were not part of the historical design of aquatic monitoring programs in the oil sands region and the absence of sufficient-ly detailed information on groundwater-surface water interactions precluded groundwater con-tributions from being considered in the design of surface water and ecological monitoring at the inception of the JOSM.

Results obtained under the groundwater theme highlight the need to address the role of ground-water when attempting to answer many of the aquatic monitoring questions associated with JOSM. In general, it is recommended that fu-ture surface water and ecological monitoring activities are designed/reconfigured to reflect the groundwater conditions/interactions found in each river and designed so that the effects of groundwater can be separated from other influences. There is a strong need to integrate groundwater influences into the monitoring re-sults from surface water (i.e. rivers, wetlands, lakes) ecosystems. As a start, this will require that groundwater assessments be conducted on all monitored rivers (and ideally wetlands), but the particular circumstances encountered may require additional (or adjustments to existing) monitoring and/or including groundwater moni-toring infrastructure at specific critical locations. Regarding the specific findings of the ground-water theme, if development proceeds along the MacKay River near the discharge areas identified in this study, it is recommended that groundwater monitoring be developed and es-tablished to appropriately monitor the ground-water discharge areas and ensure that in-stream flow needs and water quality are not adverse-ly affected by changes in groundwater condi-tions. Results to date of sub-theme B suggest that generally there is no broad-scale increased risk posed to aquatic life from groundwater dis-charging adjacent to Suncor’s Pond 1 in compar-ison to other nearby areas. Although research needs were identified for further assessments, currently no specific monitoring recommenda-tions are suggested unless future assessments identify a need.

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5. Acknowledgements

The authors wish to thank Shelley Ball, Matthew Dairon, William Govenlock, Ashley Hamilton, Jody Small, Ryan Levitt, Jason Miller, Kirsten Nickel, Megan Tobin and Miles Zurawell (Environment and Climate Change Canada-Edmonton); Andrew Basha and Bill Streeton (Environment and Climate Change Canada-Calgary); Jim Syrgiannis (Environment and Climate Change Canada-Regina); Sarah Armstrong, Newell Hedstrom, Geoff Koehler and Cuyler Onclin (Environment and Climate Change Canada-Saskatoon); Susan Brown, Jacob Burbank, Patricia Chambers, Thomas Clark, Pa-mela Collins, Linda Fan, Katherine French, Tina Hooey, Chris Kahlmeier, Braden Kralt, Kristen Leal, Amanda Malenica, Jerry Rajkumar, André Talbot, Charles Talbot, Ruth Vanderveen, John Voralek, Catherine Wong (Environment and Climate Change Canada-Burlington); Elizabeth Jamieson (Envi-ronment and Climate Change Canada-Ottawa); Rita Mroz (Environment and Climate Change Can-ada-Dartmouth); and Brian Drover (Environment and Climate Change Canada-St. John’s) for field and laboratory assistance. Access to the Athabasca River was graciously provided by Northland Forest Products (Fort McMurray, Alberta). Special appreciation is extended to the Fort McMurray offices of Alberta Environment and Sustainable Resource Development and to Water Survey of Canada. We would also like to thank the Scientific Presentation and Design Support Services of ECCC in Burlington, Ontario for their design and setup of the report is greatly appreciated. The final manuscript was improved by two anonymous external reviewers who provided constructive criti cism on an earlier draft of the manuscript. Funding for the research was provided through the Joint Oil Sands Monitoring Program co-led by the Governments of Canada and Alberta.

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