Isotope-based partitioning of streamflow in the oil sands region, northern Alberta: Towards a monitoring strategy for assessing flow sources and water quality controls

AbstractStudy regionThis study is based on the rapidly developing Athabasca Oil Sands region, northeastern Alberta.Study focusHydrograph separation using stable isotopes of water is applied to partition streamflow sources in the Athabasca River and its tributaries. Distinct isotopic labelling of snow, rain, groundwater and surface water are applied to estimate the contribution of these sources to streamflow from analysis of multi-year records of isotopes in streamflow.New hydrological insights for the regionThe results provide new insight into runoff generation mechanisms operating in six tributaries and at four stations along the Athabasca River. Groundwater, found to be an important flow source at all stations, is the dominant component of the hydrograph in three tributaries (Steepbank R., Muskeg R., Firebag R.), accounting for 39–50% of annual streamflow. Surface water, mainly drainage from peatlands, is also found to be widely important, and dominant in three tributaries (Clearwater R., Mackay R., Ells R.), accounting for 45–81% of annual streamflow. Fairly limited contributions from direct precipitation illustrate that most snow and rain events result in indirect displacement of pre-event water by fill and spill mechanisms. Systematic shifts in regional groundwater to surface-water ratios are expected to be an important control on spatial and temporal distribution of water quality parameters and useful for evaluating the susceptibility of rivers to climate and development impacts

Geoscience of Climate and Energy 13. The Environmental Hydrogeology of the Oil Sands, Lower Athabasca Area, Alberta

Shallow fresh groundwater and deep saline groundwater are used together with surface water in the extraction of bitumen from the Athabasca Oil Sands both in the surface mining and in situ operations. However, increasing efficiencies in processing technologies have reduced water use substantially and currently at least 75% of the water used in most operations is recycled water. Much concern has been expressed regarding contamination of surface waters by seepage from tailings ponds, but hydrogeological studies indicate that this is not happening; that seepage capture design is effective. Oil sands mining and in situ project licensing and operation regulations include Environmental Impact Assessments that mandate considerable hydrogeological measurement and monitoring work. However, little of this is independently evaluated for accuracy or synthesized and interpreted for the public. Recent changes in Alberta environmental regulation, including the establishment of the Alberta Environmental Monitoring Management Board (in October 2012) are expected to bring new transparency to environmental management of Oil Sands operations.SOMMAIREOn utilise conjointement des eaux douce de faibles profondeur, des eaux souterraines salines profondes avec des eaux de surface dans l'extraction du bitume des sables bitumineux de l'Athabasca, tant dans le procédé d’extraction in situ qu’en surface.  Par ailleurs, l’accroissement de l'efficacité des technologies de traitement a considérablement réduit la consommation d'eau et, à l’heure actuelle, au moins 75% de l'eau utilisée dans la majorité des opérations est de l'eau recyclée.  Beaucoup d’inquiétude a été exprimée concernant la contamination des eaux de surface par la percolation des eaux des bassins de décantation des résidus, mais des études hydrogéologiques indiquent que ce n'est pas le cas, et que le concept de capture des infiltrations est efficace.  L’octroi de permis d’exploitation ainsi que les procédés d’exploitation des sables bitumineux, par extraction en surface ou in situ, comportent des évaluations d’impact sur les milieux de vie, est assorti de mandats élaborés de mesures hydrologiques et de suivi.  Cela dit, peu de ces mesures sont évaluées de manière indépendante quant à leur exactitude, leur mise en forme et leur interprétation pour le grand public.  Les changements récents dans la réglementation environnementale en Alberta, y compris la mise en place du Alberta Environmental Monitoring Management Board (en Octobre 2012) devraient aboutir à une nouvelle transparence de la gestion environnementale de l'exploitation des sables bitumineux.DOI: http://dx.doi.org/10.12789/geocanj.2013.40.01

Modelling transverse mixing of sediment and vanadium in a river impacted by oil sands mining operations

2214-5818/© 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Alberta Environment and Parks (fund # 1-424411-1323-8000) and the University of Saskatchewan’s Global Water Futures Research Program (fund # 1-419204-1293-8000)Peer ReviewedStudy region: The lower Athabasca River was used as a test case using total suspended sediment, chloride and vanadium as the model variables. Upstream model boundary conditions included water from the tributary Clearwater River (right stream tube) and the upper Athabasca River extending upstream of the tributary mouth (left stream tube). This model will be extended to include the Peace-Athabasca Delta (PAD), to determine the implications of mining outfall discharges on a large region of the Athabasca – PAD region. Study focus: A novel, quasi-two-dimensional surface water-quality modelling approach is presented in which the model domain can be discretised in two dimensions, but a one-dimension solver can still be applied to capture water flow between the discretisation units (segments). The approach requires a river reach to be divided into two stream tubes, along the left and right river sides, with flows exchanging through the segments longitudinally and also laterally between adjacent segments along the two streams. New hydrological insights for the region: The new method allows the transverse mixing of tributary and outfall water of different constituent concentrations to be simulated along the course of the river. Additional diffuse loading of dissolved vanadium could be determined from the model’s substance balance. A scenario was then simulated in which the transport and fate of vanadium in a floodplain lake and a secondary channel was determined

Integrated Environmental Modelling Framework for Cumulative Effects Assessment

Global warming and population growth have resulted in an increase in the intensity of natural and anthropogenic stressors. Investigating the complex nature of environmental problems requires the integration of different environmental processes across major components of the environment, including water, climate, ecology, air, and land. Cumulative effects assessment (CEA) not only includes analyzing and modeling environmental changes, but also supports planning alternatives that promote environmental monitoring and management. Disjointed and narrowly focused environmental management approaches have proved dissatisfactory. The adoption of integrated modelling approaches has sparked interests in the development of frameworks which may be used to investigate the processes of individual environmental component and the ways they interact with each other. Integrated modelling systems and frameworks are often the only way to take into account the important environmental processes and interactions, relevant spatial and temporal scales, and feedback mechanisms of complex systems for CEA. This book examines the ways in which interactions and relationships between environmental components are understood, paying special attention to climate, land, water quantity and quality, and both anthropogenic and natural stressors. It reviews modelling approaches for each component and reviews existing integrated modelling systems for CEA. Finally, it proposes an integrated modelling framework and provides perspectives on future research avenues for cumulative effects assessment

Modelling of River Flows, Sediment and Contaminants Transport

This book presents five articles that are also part of a Special Issue titled: Modelling of River flows, Sediment and Contaminants Transport published in the Water Journal under the section: Water Erosion and Sediment Transport. It covers a wide range of topics, such as predicting the impacts of wildfires on sediment transport and water quality in a mountainous region and estimating the sediment erosion due to release of ice-jams in cold region rivers

An evaluation of the use of natural stable isotopes of water to track water movement through oil sands mine closure landforms

Surface mining of oil sands results in extensive land disturbance, earth movement and water usage. After mining, the disturbed landscapes must be reconstructed and reclaimed as natural landforms. There are numerous challenges associated with understanding the responses of these landforms over time, including a need to track and characterize water movement through closure landforms to understand the hydrological responses of these landforms over time. This study attempted to use natural stable isotopes of water (δD and δ18O) to identify and characterize source waters from various closure landforms at an oil sands mine site. The study area is Syncrude‟s Mildred Lake mine, an open pit oil sands mine located in northern Alberta. A variety of groundwater, surface water and soil samples from a variety of landforms (overburden dumps, composite and mature fine tailings areas, tailings sand structures and freshwater reservoirs) were collected in an attempt to fully represent the isotopic distribution of waters across the mine site. Laboratory analysis of δD and δ18O was done on all samples. The local meteoric water line first established by Hilderman (2011) was redeveloped with additional precipitation data and calculated to be δD=7.0(δ18O) -18.6‰. A natural evaporation line having a slope of 5.3 was calculated for the mine site with samples collected from three surface water ponds on the mine site. Five primary source waters were identified on the mine site: process affected water/tailings, rainfall, snow, interstitial shale water and Mildred Lake water. It was found that these sources of water generally have unique natural stable water isotope signatures. Process affected water at the site generally had an enriched signature compared to other mine waters. The enrichment was attributed to fractionation from the recycle water circuit and natural evaporation. The characterizations of these source waters were then used in several hydrogeological examples to demonstrate that natural stable water isotopes can be applied to water balance estimates and to identify water movement processes related to closure landforms

An isotopic assessment of oil sands mine site waters to improve water management practices

Current oil sands mining technology requires approximately 2 m3 in the production of 1 m3 of crude oil. This water demand has resulted in massive volumes of process-affected waters being stored on-site – a volume that is currently not well quantified, though estimated to be in in the order of billions of m3. A site wide water balance must be closed at each mine in order to effectively manage the on-site storage and reuse of process-affected waters, in addition to planning for future remediation and release of this water following site closure. Oil sands mining operators have identified the constantly evolving nature of both operational water demands and the tailings management infrastructure as key challenges preventing accurate closure of a site wide water balance. Stable isotopes of oxygen and hydrogen (18O and 2H) have been widely used as tracers to close water balances of natural reservoirs. To date, their application to mine water containment systems, such as tailings management facilities, has not yet been implemented. This study demonstrates the use of 18O and 2H as tools to track key components of the water balance associated with the Mildred Lake mine, operated by Syncrude Canada Ltd in Northern Alberta. There, process affected waters are stored in interconnected tailings ponds referred to as the recycle water (RCW) circuit, with approximately 200 million m3 of water accessible for reuse in the extraction and transport of bitumen. This thesis characterizes the primary mechanisms of each water balance component contributing to the seasonal and inter-annual evolution of isotopic signatures of the RCW circuit and an end pit lake located at Mildred Lake mine. The thesis uses isotopic “finger-printing” of contributing water sources to characterize each part of the system. Isotope mass balance techniques were implemented to estimate evaporative loss from these systems and are compared to traditional methods of estimating evaporation (e.g., Penman combination equation and eddy covariance towers). This study found that isotopic seasonality of both the RCW circuit and the end pit lake were muted compared to natural systems within the region due to the contribution of large volumes of highly enriched pore water to tailings pond water stores as a result of tailings settlement. Samples collected from tailings ponds showed a systematic shift towards greater isotopic depletion during the ice-on period. I hypothesized that this shift occurred as a result of fractionation during ice formation in addition to mixing with process water released from tailings. Such mechanisms appeared to contribute to the observable spring depletion of the RCW circuit in addition to depleted snowmelt during the spring freshet. The seasonal variations in the isotopic signatures of individual tailings ponds were consistent with differences in water management between ponds. I then used an integrated isotopic signature as a proxy for the entire RCW circuit in isotope mass balance modelling scenarios. The proportion of inflow lost to evaporation from the RCW circuit was calculated as a decimal ratio using isotope mass balance modelling. The evaporation/inflow ranged from 0.11 to 0.22 over a five-year period, consistent with a high through-flow system with low residence time. These ratios correspond to 67–133 mm yr-1 of inflow water lost to evaporation from the RCW circuit based on estimated volumes of the water balance inputs. A simplified isotope mass balance model of the RCW circuit was used to estimate evaporative losses based on observable temporal isotopic enrichment during the open water period and assuming all other outflows of the water balance were zero. Using this model evaporation rates were found to range from 418 to 931 mm yr-1, while evaporation rates measured on-site using eddy covariance ranged from 350-520 mm yr-1. The difference between the isotope mass balance and eddy covariance results suggest a contribution of highly enriched tailings pore water to the overall enrichment of the RCW circuit in addition to open water evaporation. The isotope mass balance model was also used to simulate the evolution of the daily isotopic signature of a highly monitored demonstration end pit lake. The simulated pattern of isotope evolution was used to obtain an optimized estimate of lake evaporation. This estimate was then compared to a measured water balance over a four-year period. The model showed good agreement when 18O was used as the tracer; however, when 2H was used as the tracer the model consistently under predicted open water enrichment - likely due to evaporative fractionation effects. This thesis represents the first study that we are aware of that applies isotope mass balance techniques to an engineered system within the Alberta oil sands region. Our results highlight the potential value of using stable isotope tracers to aid in on-site water management of tailings ponds as well as helping to improve our understanding of the transport and distribution of water moving through mine closure landscapes

Natural gamma-ray spectroscopy (NGS) as a proxy for the distribution of clay minerals and bitumen in the Cretaceous McMurray Formation, Alberta, Canada

Detailed examination of the mineralogy of the Cretaceous McMurray Formation within a facies framework is used to assess the use of natural gamma-ray spectroscopy (NGS) and a pulsed neutron generator (PNG) tool in delineating variation in clay mineral and bitumen contents. Characterization of the mixed-layer (interstratified) clay phases in the McMurray Formation provides an improved understanding of clay interaction in bitumen processing and tailings settling behavior, important for mine planning and tailings remediation schemes. Mineral diversity in the McMurray Formation was determined on facies attributed samples using whole rock X-ray diffraction (XRD), cation exchange capacity (CEC) measurements, elemental analysis (XRF), clay size fraction (<2 mu m) XRD analysis, reflected light microscopy, and cryogenic-scanning electron microscopy (cryo-SEM). Kaolinite was ubiquitous in the entire McMurray Formation with lower and middle McMurray Formation sediments also containing mixed-layered illite-smectite (I-S) with a low expandability approximate to 20-30%. Upper McMurray Formation sediments by contrast had higher expandability (approximate to 60-70%). In floodplain sediments of the lower McMurray Formation an additional clay mineral was quantified as a kaolinite-expandable mixed-layer (clay) mineral. The associated CEC values of this mineral are 10 times the baseline for the McMurray Formation. NGS spectra from cores showed that yields of potassium (K), uranium (U), and thorium (Th) had distinct facies associations, correlated with a clay mineral signature. The resultant indicator is capable of highlighting zones within an oil sands ore body that are empirically known, by industry, to process poorly through extraction plants. A bitumen indicator from the carbon yield derived from a PNG logging tool assesses bitumen content. NGS and PNG allow a full assessment of clay mineral (fines) and bitumen profiles, with the future prospect that these techniques could be used to assess ore and tailings behavior in near-real time

Developing pre-industrial baselines from floodplain lake sediment cores to quantify the extent of metals pollution within the Alberta Oil Sands Region

Oil sands mining operations began in 1967, but the onset of a monitoring program to assess water and sediment quality in the Athabasca River watershed began 30 years later. Consequently, no knowledge of pre-industrial, baseline conditions exists upon which current river sediment quality can be compared. This has undermined an ability to determine the relative importance of contaminants supplied by natural processes versus pollution to the Athabasca River by rapid growth of oil sands development. In this study, a paleolimnological approach was used to analyze sediment cores from five flood-influenced lakes located upstream and downstream of oil sands operations within the Alberta Oil Sands Region (AOSR). Loss-on-ignition and organic carbon and nitrogen elemental analyses were used to differentiate periods of strong and weak Athabasca River flood influence. In addition, the temporal changes in concentrations of bitumen-associated metals vanadium (V) and nickel (Ni) were explored at each lake. A pre-industrial baseline was developed using pre-1967 sediment concentrations of V and Ni, normalized to aluminum concentration, from lakes in the AOSR to estimate the natural range of variability of these metals. When normalized metals concentrations in recently deposited flood-influenced sediment were compared to the pre-industrial baseline, no evidence of enrichment in the river-derived stratigraphic intervals was detected. However, significant enrichment of bitumen-related metals V and Ni (up to 2- and 1.6-fold above the baseline, respectively) was observed in weakly flood-influenced sediment in the two floodplain lakes located closest to the most active mining operations (< 10 km), indicating local atmospheric pollution. Athabasca River sediment data collected by regional monitoring programs RAMP (1997-2002) and JOSM (2012-2014) were examined in the context of the newly developed baselines and showed enrichment of V (1.2-1.7x baseline) and Ni (1.2-2.0x baseline) at some of the river monitoring sites, usually proximal to tributary outflows. This research indicates that sediment profiles from floodplain lakes along the lower Athabasca provide valuable information as pre-industrial depositional areas of natural sediment metals. Paleohydrological analyses, however, indicate that flood-influence at many of these lakes is declining, coincident with oil sands growth, and so many of the lakes no longer frequently capture flood sediments. Nonetheless, metal-specific baselines using the pre-1967 data can be used to detect enrichment in modern sediments of the floodplain lakes and in river sediment monitoring data, the latter previously criticized for inadequate baseline knowledge, and which also now serves as a foundation for ongoing river sediment monitoring

The hydrology and geochemistry of a saline spring fen peatland in the Athabasca oil sands region of Alberta

Due to the nature of the regional geology and the bitumen extraction process, the post-mined landscape of Canada’s oil sands region will have a much higher concentration of dissolved salts than it did prior to mining. As a result, naturally saline wetlands may constitute appropriate reclamation targets and knowledge of saline wetland hydrology can provide important clues to their form and function. Furthermore, the presence of saline discharge features in the Athabasca oil sands region (AOSR) provides an opportunity to study more closely the nature of groundwater flow in a region of considerable hydrogeologic complexity, including the origin and flow history of brines and the link between springs, subsurface wastewater containment and surface water quality. A low-flow saline-spring fen peatland located adjacent to a proposed in-situ oil extraction facility was examined south of the oil sands hub of Fort McMurray, Alberta. Hydrologically disconnected from underlying Devonian deposits that are a typical source of salinity, a saline groundwater plume originating from a Lower Cretaceous aquifer (the Grand Rapids Formation) was identified as a likely source for the accumulation of Na+ (mean of 6,949 mg L-1) and Cl- (mean of 13,766 mg L-1) in fen groundwater. Considerable spatial variability in ground and surface water salinity was observed, with the concentration of dissolved salts decreasing by an order of magnitude in the direction of flow. A sharp decrease in near-surface salinity was found along the entire perimeter between the fen and adjacent freshwater wetlands. Patterns in deep groundwater flux were difficult to interpret due to possible inaccuracies associated with the piezometer network (e.g., time-lag errors in low hydraulic conductivity substrates), and rates of groundwater input were estimated to be small (< 1 mm over a season) due to the low conductivity of the underlying mineral till (5.5x10-7 cm s-1). Water table dynamics were exaggerated in response to wetting and drying for both study seasons and the fen’s small subsurface storage capacity was readily exceeded under periods of sustained rainfall. The large pond network functioned as an effective transmitter of surface water during periods of high water table but was a sink of groundwater during dry periods due to high rates of evaporation. Despite flooding conditions observed in 2012, groundwater exchange between the fen and adjacent wetlands was low and the rough microtopography worked to detain surface waters and restrict runoff in the fen’s lower reaches. Together these mechanisms worked to isolate the saline fen and restrict the flux of saline waters into the surrounding landscape. Elevated concentrations of dissolved salts in nearby wetland and river systems indicates that influence of saline discharge is not solely restricted to the region’s major river systems. The flux of salt from saline wetlands may play an important role in the overall water quality of groundwater and receiving water bodies (e.g., nearby river systems). The geochemical signature of fen groundwater points to halite as a source of salinity, as indicated by Cl-/Br- ratios in excess of 7,000. This is in contrast to what has been observed for regional formation brines that are typically related to evaporated seawater. Isotopic evidence and relatively low salinities compared to springs in the Wood Buffalo region suggests that fen discharge water may be significantly diluted as a result of mixing with freshwater sources. The contribution of evaporite to discharge water may be coming from somewhere deeper and further south in the basin. This has important implications for the disposal of wastewater by deep well injection, as disposal zones may be hydrologically linked to near-surface aquifers and discharge features well beyond the immediate production and storage area