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Oil sands development in the lower Athabasca River watershed has raised considerable public and scientific concerns regarding perceived effects on environmental health. To address this issue for tributaries and the mainstem of the Athabasca River in the Athabasca Oil Sands Region, the Water Component of the Joint Oil Sands Monitoring (JOSM) plan produced monitoring assessments for seven integrated themes: atmospheric deposition, tributary water quality, river mainstem water quality, groundwater quality and quantity, water quality and quantity modelling, benthic invertebrate condition, and fish health. Our review integrates and synthesizes the large and diverse datasets assembled in the seven JOSM theme assessments to (i) evaluate possible environmental effects based on known sources and candidate proximal causes and (ii) determine the importance of cause-and-effect pathways related to contaminant, sediment, and nutrient inputs. Although JOSM research identified ecological effects that appear to be associated with contaminant exposure, the source of this exposure is confounded by co-location of, and inability to differentiate between, oil sands operations (principally released by atmospheric emission) and inputs from the natural bitumen outcrops (e.g., erosional material transported by surface and groundwater flows). Nutrient enrichment from treated municipal sewage effluent was the dominant ecological effect observed for the mainstem Athabasca River, associated with increased fish size and changes in invertebrate assemblages, likely because this pollution source is discharged directly into the river. If the direct release of treated oil sands process water occurs in the future, then the potential ecological impact of these direct industry releases will need to be evaluated carefully. The ecological causal assessment method proved to be a useful tool for better understanding how stressor sources relate to ecological effects through candidate proximate causes. Factors that confound our ability to assess the ecological effects of oil sands development focus on our inability to adequately differentiate between contaminants supplied from natural and anthropogenic contaminant sources. Our causal synthesis identifies options for changes in future monitoring to better anticipate and detect degradation in the ecosystem health of the lower Athabasca River and its tributaries.

This study developed and applied a framework for assessing the vulnerability of pan-Canadian water resources to permafrost thaw. The national-scale work addresses a key, but neglected, information gap, as previous research has focused on small scale physical processes and circumpolar trends. The framework was applied to develop the Canadian Water Resources Vulnerability Index to Permafrost Thaw (CWRVIPT) and map the index across the Canadian North. The CWRVIPT is a linearly additive index of permafrost, terrain, disturbance, and climatic conditions and stressors that influence water budgets and aquatic chemistry. Initial results imply water resources in the western Northwest Territories and Hudson Bay Lowlands are most vulnerable to permafrost thaw; however, water resources on Banks, Victoria and Baffin Islands are also relatively vulnerable. Although terrain and permafrost sub-indices are the largest component of the CWRVIPT across a wide swath from the Mackenzie River Delta to the Hudson Bay Lowlands, the climate sub-index is most important farther north over parts of the southern portion of the Arctic Archipelago. The index can be used to identify areas of water resource vulnerability on which to focus observation and research in the Canadian North.

The western cordillera supplies freshwater across much of western Canada mainly through meltwater from snow and ice. This “alpine water tower” has been, and is projected to be, associated with changes in the seasonality and amount of freshwater availability, which are critical in supporting the societal and environmental flow needs of the region. This study incorporates existing information to synthesize and evaluate current and future freshwater supplies and demands across major north-, west-, and east-flowing sub-basins of the Canadian western cordillera. The assessment of supply indicators reveals several historical changes that are projected to continue, and be exacerbated, particularly by the end of this century and under a high emission scenario. The greatest and most widespread impact is the seasonality of streamflow characterized by earlier spring freshets, increased winter, and decreased summer flow. Future winter and spring warming over all basins will result in decreases in end of season snow and glacier mass balance with greatest declines in more southern regions. In many areas, there will be a greater likelihood of summer freshwater shortages. All sub-basins have environmental and economic freshwater demands and pressures, especially in more southern watersheds where population and infrastructure are more prevalent and industrial, agricultural, and water energy needs are higher. Concerns regarding the continued ability to maintain suitable aquatic habitats and adequate water quality are issues across all regions. These water supply changes along with continued and increasing demands will combine to create a variety of freshwater vulnerabilities across all regions of western Canada. Southern basins including the South Saskatchewan and Okanagan are likely to experience the greatest vulnerabilities due to future summer freshwater supply shortages and increasing economic demands. In more northern areas, vulnerabilities primarily relate to how the rapidly changing landscape (mainly associated with permafrost thaw) impacts freshwater quantity and quality. These vulnerabilities will require various adaptation measures in response to alterations in the timing and amount of future freshwater supplies and demands.

In contrast to a large body of scientific literature that is based on empirical data and physically based and mathematical analyses, Wolfe et al. (2020) cited proxy-based paleolimnological evidence and argued that the regulation of Peace River has not played a role in the reduced incidence of large ice-jam floods. Such events are essential to the sustenance of perched basins located in the Peace Sector of the Peace–Athabasca Delta. Herein, the arguments advanced by Wolfe et al. (2020) are critically examined and shown to be unconvincing. Relevant literature indicates that a drying trend was first noticed after construction of the Bennett Dam. It is shown, moreover, that the belatedly questioned Traditional Knowledge and Historical ice-jam flood record is a reliable source of information, at least with respect to large floods, which are crucial to perched-basin replenishment. Detailed examination of the Wolfe et al. (2020) magnetic susceptibility (MS) profiles and their interpretation points to serious inconsistencies and leads to a renewed recommendation for coring perched, rather than readily flooded, basins in the future. It is also recommended that the oxbow lakes cored nearly two decades ago be revisited to obtain updated MS profiles. Deficiencies in the interpretation of inferred isotopic-composition time series of three perched basins suggest that all factors influencing such environmental variables be considered before drawing conclusions regarding the frequency of past floods.

Lakes are important sources of freshwater and provide essential ecosystem services. Monitoring their spatial and temporal variability, and their functions, is an important task within the development of sustainable water management strategies. The Surface Water and Ocean Topography (SWOT) mission will provide continuous information on the dynamics of continental (rivers, lakes, wetlands and reservoirs) and ocean water bodies. This work aims to contribute to the international effort evaluating the SWOT satellite (2022 launch) performance for water balance assessment over large lakes (e.g., >100 km2). For this purpose, a hydrodynamic model was set up over Mamawi Lake, Canada, and different wind scenarios on lake hydrodynamics were simulated. The derived water surface elevations (WSEs) were compared to synthetic elevations produced by the Jet Propulsion Laboratory (JPL) SWOT high resolution (SWOT-HR) simulator. Moreover, water storages and net flows were retrieved from different possible SWOT orbital configurations and synthetic gauge measurements. In general, a good agreement was found between the WSE simulated from the model and those mimicked by the SWOT-HR simulator. Depending on the wind scenario, errors ranged between approximately −2 and 5 cm for mean error and from 30 to 70 cm root mean square error. Low spatial coverage of the lake was found to generate important biases in the retrievals of water volume or net flow between two satellite passes in the presence of local heterogeneities in WSE. However, the precision of retrievals was found to increase as spatial coverage increases, becoming more reliable than the retrievals from three synthetic gauges when spatial coverage approaches 100 %, demonstrating the capabilities of the future SWOT mission in monitoring dynamic WSE for large lakes across Canada.

River ice, like open-water conditions, is an integral component of the cold-climate hydrological cycle. The annual succession of river ice formation, growth, decay and clearance can include low flows and ice jams, as well as midwinter and spring break-up events. Reports and associated data of river ice occurrence are often limited to single locations or regional assessments, are season-specific, and use readily available data. Within Canada, the National Hydrometric Program (NHP) operates a network of gauging stations with water level as the primary measured variable to derive discharge. In the late 1990s, the Water Science and Technology Directorate of Environment and Climate Change Canada initiated a long-term effort to compile, archive and extract river-ice-related information from NHP hydrometric records. This data article describes the original research data set produced by this near 20-year effort: the Canadian River Ice Database (CRID). The CRID holds almost 73 000 recorded variables from a subset of 196 NHP stations throughout Canada that were in operation within the period 1894 to 2015. Over 100 000 paper and digital files were reviewed, representing 10 378 station years of active operation. The task of compiling this database involved manual extraction and input of more than 460 000 data entries on water level, discharge, ice thickness, date, time and data quality rating. Guidelines on the data extraction, rating procedure and challenges are provided. At each location, time series of up to 15 variables specific to the occurrence of freeze-up and winter-low events, midwinter break-up, ice thickness, spring break-up, and maximum open-water level were compiled. This database follows up on several earlier efforts to compile information on river ice, which are summarized herein, and expands the scope and detail for use in Canadian river ice research and applications. Following the Government of Canada Open Data initiative, this original river ice data set is available at https://doi.org/10.18164/c21e1852-ba8e-44af-bc13-48eeedfcf2f4 (de Rham et al., 2020).

Significance Too often, ecological monitoring studies are designed without understanding whether they have sufficient statistical power to detect changes beyond natural variability. The Peace–Athabasca Delta is North America’s largest inland delta, within a World Heritage area, and is currently threatened by human development. Using multispecies occupancy models we show that the wetland macroinvertebrate community is highly diverse, and spatial and temporal turnover are so high that composition is nearly random, emphasizing stochastic processes of assembly. Using DNA metabarcoding, our study detected more taxa, both overall and per sample, than traditional morphology-based sample processing, increasing our power to detect ecosystem change. Improving data quality and quantifying error are key to delivering effective monitoring and understanding the dynamic structure of the metacommunity., The complexity and natural variability of ecosystems present a challenge for reliable detection of change due to anthropogenic influences. This issue is exacerbated by necessary trade-offs that reduce the quality and resolution of survey data for assessments at large scales. The Peace–Athabasca Delta (PAD) is a large inland wetland complex in northern Alberta, Canada. Despite its geographic isolation, the PAD is threatened by encroachment of oil sands mining in the Athabasca watershed and hydroelectric dams in the Peace watershed. Methods capable of reliably detecting changes in ecosystem health are needed to evaluate and manage risks. Between 2011 and 2016, aquatic macroinvertebrates were sampled across a gradient of wetland flood frequency, applying both microscope-based morphological identification and DNA metabarcoding. By using multispecies occupancy models, we demonstrate that DNA metabarcoding detected a much broader range of taxa and more taxa per sample compared to traditional morphological identification and was essential to identifying significant responses to flood and thermal regimes. We show that family-level occupancy masks high variation among genera and quantify the bias of barcoding primers on the probability of detection in a natural community. Interestingly, patterns of community assembly were nearly random, suggesting a strong role of stochasticity in the dynamics of the metacommunity. This variability seriously compromises effective monitoring at local scales but also reflects resilience to hydrological and thermal variability. Nevertheless, simulations showed the greater efficiency of metabarcoding, particularly at a finer taxonomic resolution, provided the statistical power needed to detect change at the landscape scale.

Anthropogenic and climatic‐induced changes to flow regimes pose significant risks to river systems. Northern rivers and their deltas are particularly vulnerable due to the disproportionate warming of the Northern Hemisphere compared with the Southern Hemisphere. Of special interest is the Peace–Athabasca Delta (PAD) in western Canada, a productive deltaic lake and wetland ecosystem, which has been recognized as a Ramsar site. Both climate‐ and regulation‐induced changes to the hydrological regime of the Peace River have raised concerns over the delta's ecological health. With the damming of the headwaters, the role of downstream unregulated tributaries has become more important in maintaining, to a certain degree, a natural flow regime, particularly during open‐water conditions. However, their flow contributions to the mainstem river under future climatic conditions remain largely uncertain. In this study, we first evaluated the ability of a land‐surface hydrological model to simulate hydro‐ecological relevant indicators, highlighting the model's strengths and weaknesses. Then, we investigated the streamflow conditions in the Smoky River, the largest unregulated tributary of the Peace River, in the 2071–2100 versus the 1981–2010 periods. Our modelling results revealed significant changes in the hydrological regime of the Smoky River, such as increased discharge in winter (+190%) and spring (+130%) but reduced summer flows (−33%) in the 2071–2100 period compared with the baseline period, which will have implications for the sustainability of the downstream PAD. In particular, the projected reductions in 30‐day and 90‐day maximum flows in the Smoky River will affect open‐water flooding, which is important in maintaining lake levels and connectivity to perimeter delta wetlands in the Peace sector of the PAD. The evaluation of breakup and freeze‐up flows for the 2071–2100 period showed mixed implications for the ice‐jam flooding, which is essential for recharging high‐elevation deltaic basins. Thus, despite projected increase in annual and spring runoff in the 2071–2100 period from the Smoky sub‐basin, the sustainability of the PAD still remains uncertain.

The origins of the Surface Water and Ocean Topography (SWOT) mission date back to the mid-1970s with the launch of GOES-3 and SEASAT. These missions were then followed in 1992 by the Topex-Poseidon...

The Peace-Athabasca Delta (PAD) in one of the largest (~6000 km2) freshwater deltaic ecosystem in the world. This low relief, deltaic floodplain formed at the confluence of the Peace-Athabasca-Birch rivers the west end of Lake Athabasca in northwestern Canada. Small changes in water level/depth have important implications for surface water connectivity and associated habitat quality The floodplains contain more than 1000 wetland-lake basins with varying degrees of connectivity to the main flow system. Hydroperiod is influenced by occasional ice-jam and open-water inundations that recharge wetland basins. This culturally important and biologically rich delta is a Ramsar Convention Wetland Site of International Importance, and is a key feature of the Wood Buffalo National Park (WBNP) that is listed as a UNESCO World Heritage Site. The PAD ecosystem is influenced by contributing basin and local scale hydrological stressors from flow regulation (eg, hydroelectric dam, weirs), water and land use (eg, oil sands mining) and climate change.Growing concern regarding increased cumulative effects on the delta led Indigenous Peoples petitioning UNESCO World Heritage Committee (WNC) to reassess the protection status of the park. The WBNP Action Plan was developed to address 17 UNESCO WHC recommendations to ensure maintenance of Outstanding Universal Value of the Park. One key set of recommendations is to: 1) Conduct environmental flows assessments, to the highest international standard, in order to identify water flows needed to sustain the ecological functioning of the PAD under current and projected development and climate change; 2) Establish adequate baseline hydrological information for PAD assessments.A significant scientific effort has been invested in the last four decades, particularly since 2010, in improving our understanding the relationship between streamflow, landscape controls and aquatic ecology in this cold-regions delta. This information is key to assess historical and present states, learn from past development to inform planned development, and prepare for anticipated future hydro-ecological changes. However, several key questions arise regarding what is the best approach to preparing for the future and managing such a complex system, what management options are possible within an environmental flow framework given known hydrological stressors, and what future ecosystem state does society want for the delta. The goal of this presentation focused on the PAD is threefold: i) Provide an overview of major hydro-ecological research and water management; ii) Assess the potential applicability of riverine environmental flow frameworks to deltaic floodplain environments; and iii) Explore the development of an environmental flow/water level framework and tools necessary to assess and manage changes to the aquatic ecology of this internationally important deltaic ecosystem.

Climatic change is affecting streamflow regimes of the permafrost region, altering mean and extreme streamflow conditions. In this study, we analyzed historical trends in annual mean flow (Qmean), minimum flow (Qmin), maximum flow (Qmax) and Qmax timing across 84 hydrometric stations in the permafrost region of Canada. Furthermore, we related streamflow trends with temperature and precipitation trends, and used a multiple linear regression (MLR) framework to evaluate climatic controls on streamflow components. The results revealed spatially varied trends across the region, with significantly increasing (at 10% level) Qmin for 43% of stations as the most prominent trend, and a relatively smaller number of stations with significant Qmean, Qmax and Qmax timing trends. Temperatures over both the cold and warm seasons showed significant warming for &gt, 70% of basin areas upstream of the hydrometric stations, while precipitation exhibited increases for &gt, 15% of the basins. Comparisons of the 1976 to 2005 basin-averaged climatological means of streamflow variables with precipitation and temperature revealed a positive correlation between Qmean and seasonal precipitation, and a negative correlation between Qmean and seasonal temperature. The basin-averaged streamflow, precipitation and temperature trends showed weak correlations that included a positive correlation between Qmin and October to March precipitation trends, and negative correlations of Qmax timing with October to March and April to September temperature trends. The MLR-based variable importance analysis revealed the dominant controls of precipitation on Qmean and Qmax, and temperature on Qmin. Overall, this study contributes towards an enhanced understanding of ongoing changes in streamflow regimes and their climatic controls across the Canadian permafrost region, which could be generalized for the broader pan-Arctic regions.

A project was constructed to integrate remotely sensed data from multiple sensors and platforms to characterize range of ecosystem characteristics in the Peace–Athabasca Delta in Northern Alberta, Canada. The objective of this project was to provide a framework for the processing of multisensor data to extract ecosystem information describing complex deltaic wetland environments. The data used in this study was based on a passive satellite-based earth observation multispectral sensor (Sentinel-2) and airborne discrete light detection and ranging (LiDAR). The data processing strategy adopted here allowed us to employ a data mining approach to grouping of the input variables into ecologically meaningful clusters. Using this approach, we described not only the reflective characteristics of the cover, but also ascribe vertical and horizontal structure, thereby differentiating spectrally similar, but ecologically distinct, ground features. This methodology provides a framework for assessing the impact of ecosystems on radiance, as measured by Earth observing systems, where it forms the basis for sampling and analysis. This final point will be the focus of future work.

River ecosystems have adapted to a natural range of variability in magnitude, timing, duration, and predictability of key hydrograph components, such as high- and low-flow periods. However, the timing, magnitude, and variability of cold region flow regimes are changing in response to a warming climate, water abstraction, and building of impoundments. Changes in water quantity flowing down a river at a given time have the potential to adversely and/or positively affect habitat conditions and sustainability of ecological diversity within both the river and associated riparian and floodplain zones. There is a growing need to incorporate environmental flow assessments in the management of permafrost regions in response to changing flow regimes in order to preserve these diverse ecosystems. Environmental flows are defined as the quantity, timing, and quality of freshwater flows and levels necessary to sustain aquatic ecosystems. The goal of this Chapter is to present an overview of environmental flows for permafrost regions, with a focus on North America where information is most readily available. This goal is achieved via a review of (i) cold regions hydro-ecology, (ii) history and application of environmental flows internationally, (iii) environmental flow guidelines and policy in Arctic states, and (iv) riverine monitoring in northern regimes to support environmental flow frameworks. Several key recommendations to address knowledge and data gaps to better manage natural resources are provided.

This chapter provides an overview on the range of hydrologic extremes occurring in Arctic Rivers, consisting of extreme low winter flows; river-ice jam breakup spring floods; snowmelt-driven peak spring/early summer flows; and in some instances, rainfall-driven peak flows in summer. These extreme conditions are mainly influenced by climatological drivers, and in particular, warming climate and enhanced wetness is causing substantial changes in the magnitude, variability and timing of extreme events. The most prominent historical changes in the Arctic include increasing trends in mean annual flow and winter low flow, and earlier timing of peak flow, which are attributable to warming temperature and increasing precipitation, and resulting changes in snowpack storage. Winter low flow is further enhanced by permafrost degradation as it promotes increased soil infiltration and subsurface water movement. Snowmelt-driven annual maximum flow, primarily, has been decreasing, consistent with increased warming and decreased snowpack. Secondary peak flow events in late summer, driven by extreme summer rainfall and possibly enhanced by glacial melt, have been occurring more frequently in some areas of the Arctic, exceeding snowmelt-driven peak flow events. There is also evidence of nonstationary changes in streamflow extremes, such as increasing recurrence intervals of snowmelt-driven floods of a particular magnitude. Future projections indicate continued and enhanced warming, and strong increases in the high-latitude precipitation leading to enhanced annual flows and low flows. Future changes in peak flow remain unclear as peak flow could either increase or decrease depending on the region and interactions between precipitation change and temperature increases. Alterations in hydrologic extremes in the Arctic will have major social and economic implications; thus, focused research aimed at understanding, predicting, and projecting the Arctic streamflow extremes is recommended.

Lakes are important sources of freshwater and provide essential ecosystem services. Monitoring their spatial and temporal variability, as well as of their functions, is an important task within the development of sustainable water management strategies. The Surface Water and Ocean Topography (SWOT) mission will provide continuous information on the dynamics of continental (rivers, lakes, wetlands and reservoirs) and ocean water bodies. This work aims to contribute to the international effort evaluating the SWOT satellite (2022 launch) performance for water balance assessment over large lakes (e.g., > 100 km2). For this purpose, a hydrodynamic model was set up over Mamawi Lake, Canada, and different wind scenarios on lake hydrodynamics were simulated. The derived water surface elevations (WSE) were compared to synthetic elevations produced by the Jet Propulsion Laboratory (JPL) SWOT high resolution (SWOT-HR) simulator. Moreover, water storages and net flows were retrieved from different possible SWOT orbital configurations, as well as synthetic gauge measurements. In general, a good agreement was found between the WSE simulated from the model and those mimicked by the SWOT-HR simulator. Depending on the wind scenario, errors ranged between approximately −2 and 5 cm for mean error, and 30 to 70 cm root mean square error. Low spatial coverage of the lake was found to generate important biases in the retrievals of water volume or net flow between two satellite passes in the presence of local heterogeneities in WSE. However, the precision of retrievals was found to increase as spatial coverage increases, becoming more reliable than the retrievals from 3 synthetic gauges when spatial coverage approaches 100 %, demonstrating the capabilities of the future SWOT mission in monitoring dynamic WSE for large lakes across Canada.

Hydraulic models require water extents (WE) and water levels (WL) for their calibration and validation. The synthetic aperture radar (SAR) has been readily used in the past to delineate wat...

Wetlands have and continue to undergo rapid environmental and anthropogenic modification and change to their extent, condition, and therefore, ecosystem services. In this first part of a two-part review, we provide decision-makers with an overview on the use of remote sensing technologies for the ‘wise use of wetlands’, following Ramsar Convention protocols. The objectives of this review are to provide: (1) a synthesis of the history of remote sensing of wetlands, (2) a feasibility study to quantify the accuracy of remotely sensed data products when compared with field data based on 286 comparisons found in the literature from 209 articles, (3) recommendations for best approaches based on case studies, and (4) a decision tree to assist users and policymakers at numerous governmental levels and industrial agencies to identify optimal remote sensing approaches based on needs, feasibility, and cost. We argue that in order for remote sensing approaches to be adopted by wetland scientists, land-use managers, and policymakers, there is a need for greater understanding of the use of remote sensing for wetland inventory, condition, and underlying processes at scales relevant for management and policy decisions. The literature review focuses on boreal wetlands primarily from a Canadian perspective, but the results are broadly applicable to policymakers and wetland scientists globally, providing knowledge on how to best incorporate remotely sensed data into their monitoring and measurement procedures. This is the first review quantifying the accuracy and feasibility of remotely sensed data and data combinations needed for monitoring and assessment. These include, baseline classification for wetland inventory, monitoring through time, and prediction of ecosystem processes from individual wetlands to a national scale.

Understanding the physical and biological mechanisms contributing to flow velocity–ecology relationships is crucial for successful river management. The application of an ecological traits-based approach offers the potential to explore mechanistic linkages between aquatic communities and a hydrological gradient. To date, however, studies focused on identifying these relationships have been limited by a lack of large-scale, long-term biological data. To address this gap at a scale relevant for water policy management, we employed data from a large-scale standardised benthic monitoring program—the Canadian Aquatic Biomonitoring Network—obtained from wadeable river sites across Canada. We applied the Threshold Indicator Taxa ANalysis method to quantify the response of the macroinvertebrate community, expressed as traditional taxonomic information and also as ecological traits, along a flow velocity gradient in reference and potential reference sites. Five key findings emerged: (1) using taxa and trait modalities revealed different flow velocity thresholds, (2) trait flow velocity indicators were less variable than taxon indicators, especially for positively responding trait modalities, (3) labile and non-labile trait modalities demonstrated highly similar patterns along the flow velocity gradient, (4) taxa from 12 different orders responded negatively to flow velocity, while only EPT taxa and some dipterans responded positively to flow velocity, and (5) traits related to mobility and ecology (e.g. climber and swimmer habits, preference of cold-cool eurythermal water and ability to survive desiccation) tended to respond positively to flow velocity, while traits related to morphology, life history and ecology (e.g. sprawler and burrower habits, preference for warm eurythermal water and inability to survive desiccation) tended to respond negatively to flow velocity. Providing ecologically based flow management targets can improve management plans, anticipate ecosystem consequences of anthropogenic change and support the development of policies to mitigate anthropogenic flow alteration. While our taxon and trait modality flow indicators were developed for Canadian watersheds, our methods to develop flow indicators and thresholds are transferrable to other systems where long-term biomonitoring programs are being developed, underscoring the need for long-term biomonitoring programs to support better ecosystem management.

We compared median runoff (R) and precipitation (P) relationships over 25 years from 20 mesoscale (50 to 5,000 km2) catchments on the Boreal Plains, Alberta, Canada, to understand controls on water sink and source dynamics in water-limited, low-relief northern environments. Long-term catchment R and runoff efficiency (RP−1) were low and varied spatially by over an order of magnitude (3 to 119 mm/year, 1 to 27%). Intercatchment differences were not associated with small variations in climate. The partitioning of P into evapotranspiration (ET) and R instead reflected the interplay between underlying glacial deposit texture, overlying soil-vegetation land cover, and regional slope. Correlation and principal component analyses results show that peatland-swamp wetlands were the major source areas of water. The lowest estimates of median annual catchment ET (321 to 395 mm) and greatest R (60 to 119 mm, 13 to 27% of P) were observed in low-relief, peatland-swamp dominated catchments, within both fine-textured clay-plain and coarse-textured glacial deposits. In contrast, open-water wetlands and deciduous-mixedwood forest land covers acted as water sinks, and less catchment R was observed with increases in proportional coverage of these land covers. In catchments dominated by hummocky moraines, long-term runoff was restricted to 10 mm/year, or 2% of P. This reflects the poor surface-drainage networks and slightly greater regional slope of the fine-textured glacial deposit, coupled with the large soil-water and depression storage and higher actual ET of associated shallow open-water marsh wetland and deciduous-forest land covers. This intercatchment study enhances current conceptual frameworks for predicting water yield in the Boreal Plains based on the sink and source functions of glacial landforms and soil-vegetation land covers. It offers the capability within this hydro-geoclimatic region to design reclaimed catchments with desired hydrological functionality and associated tolerances to climate or land-use changes and inform land management decisions based on effective catchment-scale conceptual understanding.

The complexity and natural variability of ecosystems present a challenge for reliable detection of change due to anthropogenic influences. This issue is exacerbated by necessary trade-offs that reduce the quality and resolution of survey data for assessments at large-scales. The Peace-Athabasca Delta (PAD) is a large inland wetland complex in northern Alberta, Canada. Despite its geographic isolation, the PAD is threatened by encroachment of oil sands mining in the Athabasca watershed, and hydroelectric dams in the Peace watershed. Methods capable of reliably detecting changes in ecosystem health are needed to evaluate and manage risks. Between 2011 and 2016, aquatic macroinvertebrates were sampled across a gradient of wetland flood frequency, applying both microscope-based morphological identification, and DNA metabarcoding. Using multi-species occupancy models, we demonstrate that DNA metabarcoding detected a much broader range of taxa and more taxa per sample compared to traditional morphological identification, and was essential to identifying significant responses to flood and thermal regimes. We show that family-level occupancy masks high variation among genera, and for the first time, quantify the bias of barcoding primers on the probability of detection in a natural community. Interestingly, patterns of community assembly were near random, suggesting a strong role of stochasticity in the dynamics of the metacommunity. This variability seriously compromises effective monitoring at local scales, but also reflects resilience to hydrological and thermal variability. Nevertheless, simulations showed the greater efficiency of metabarcoding, particularly at a finer taxonomic resolution, provided the statistical power needed to detect change at the landscape scale.

It is a common practice to employ hydrologic models for assessing present and future states of watersheds and assess the degree of alterations for a range of hydrologic indicators. Previous studies indicate that the hydrologic model may not be able to replicate some of the indicators of interest, which raises questions on the reliability of model simulated changes. Hence, we initiated a study to evaluate the replicability of the streamflow changes by employing the widely used variable infiltration capacity hydrologic model for sub-basins and mainstem of the Fraser River Basin, Canada. Given that the hydrologic regime of the region is known to be influenced by teleconnections to the Pacific Decadal Oscillation (PDO) and El Nino–Southern Oscillation (ENSO), we used hydrologic responses to the PDO and ENSO states as analogues for evaluating the model's ability to simulate climate-induced changes. The results revealed that the qualitative patterns of response, such as lower flows for the warm PDO state compared to the cool state, and progressively higher flows for the warm, neutral and cool ENSO states, were generally well reproduced for most hydrologic indicators. Additionally, while the directions of change between the different PDO and ENSO states were mostly well replicated, the magnitude of change for some of the indicators showed considerable differences. Hence, replicability of both magnitude and direction of change need to be carefully examined before using the simulated indicators for assessing future hydrologic changes, and a reliable replication increases the confidence of projected changes. Copyright © 2016 Her Majesty the Queen in Right of Canada. Hydrological Processes. © 2016 John Wiley & Sons, Ltd.

Floods are widely recognized as a common and largely distributed natural hazard with potential for causing loss of life, property damage, disruption of the economy and environmental damages. All geographic regions of Canada are susceptible to the deleterious impacts of floods. Recent flood events in Canada and elsewhere have contributed to the common perception that floods and associated damages have been increasing in recent years. Given the ubiquitous nature of this hazard, a thorough examination of the many complex and interrelated aspects of natural and man-made floods in Canada is long overdue. This special issue contains 27 papers dealing with a variety of different aspects of floods in Canada. The first 16 papers deal with physical aspects of floods and include a collection of case study papers that present recent flood events in Canada, following a common format to allow readers to compare and contrast recent flood events in different regions of Canada. The last 11 papers focus on ecological, soci...

This paper provides an overview of the key processes that generate floods in Canada, and a context for the other papers in this special issue – papers that provide detailed examinations of specific floods and flood-generating processes. The historical context of flooding in Canada is outlined, followed by a summary of regional aspects of floods in Canada and descriptions of the processes that generate floods in these regions, including floods generated by snowmelt, rain-on-snow and rainfall. Some flood processes that are particularly relevant, or which have been less well studied in Canada, are described: groundwater, storm surges, ice-jams and urban flooding. The issue of climate change-related trends in floods in Canada is examined, and suggested research needs regarding flood-generating processes are identified.

Widespread permafrost degradation in Canada's western Arctic has led to formation of shoreline retrogressive thaw slumps (SRTS), a process influential in modifying water and biogeochemical balances of tundra lakes. To investigate hydrological effects of SRTS, water sampling campaigns were conducted in 2004, 2005, and 2008 for paired lakes (undisturbed vs SRTS) in the upland region adjacent to the Mackenzie Delta, Northwest Territories, Canada. An isotope mass balance model to estimate evaporation/inflow, precipitation/inflow, water yield, and runoff ratio was developed incorporating seasonal evaporative drawdown effects and a mixing model to simulate gradients in marine-continental atmospheric moisture. Site-specific water balance results revealed systematically higher evaporation/inflow and precipitation/inflow for lakes with active SRTS compared to undisturbed lakes, and typically higher ratios of these indicators associated with stabilized versus active SRTS. Water yields were higher for active SRTS sites compared to undisturbed and stabilized SRTS sites, suggesting that slumping is an initial but not a sustained source of water delivery to lakes. Catchments with wildfire history were found to have lower water yields, attributed to reduced permafrost influence on runoff generation. Conceptually, we define a permafrost thaw trajectory whereby undisturbed sites, active SRTS, stabilized SRTS, and ancient SRTS represent progressive stages of permafrost thaw. We postulate that release of additional runoff is mainly due to permafrost thaw in active SRTS, which also promotes lake expansion, talik formation, and subsurface connectivity. Eventual stabilization of slumps and reduced runoff is expected once permafrost thaw sources are exhausted, at which time lakes may become more reliant on replenishment by direct precipitation. The effect of snow catch in slumps appears to be subordinate to permafrost thaw sources based on eventual decline in runoff once thaw slumps stabilize. Improved, site-specific hydrologic understanding is expected to assist with ongoing research into carbon cycling and biogeochemical feedbacks in the region.

Satellite instruments operating in the thermal infrared wavelength range >3 µm provide information for applications such as land surface temperature (LST), sea surface temperatures (SST), land surface emissivity, land classification, soil composition, volcanology, fire radiative power, cloud masking, aerosols, and trace gases. All these instruments are dependent on blackbody (BB) calibration sources to provide the traceability of the radiometric calibration to SI (Système International d’Unités). A key issue for flight BB sources is to maintain the traceability of the radiometric calibration from ground to orbit. For example, the temperature of the BB is measured by a number of precision thermometers that are calibrated against a reference Standard Platinum Resistance Thermometer (SPRT) to provide the traceability to the International Temperature Scale of 1990 (ITS-90). However, once calibrated the thermometer system is subject to drifts caused by on-ground testing, the launch and space environments. At best the uncertainties due to thermometer ageing can only be estimated as there is no direct method for recalibrating. Comparisons with other satellite sensors are useful for placing an upper limit on calibration drifts but do not themselves provide a traceable link to the SI. In this paper, we describe we describe some of the technology developments, including phase change cells for use as reference standards, thermometer readout electronics and implementation of novel coatings, that are in progress to enhance the traceability of flight calibration systems in the thermal infrared.

The Peace-Athabasca Delta (PAD) in northern Alberta is one of the world's largest inland freshwater deltas, home to many species of fish, mammals, and birds. Coincident with regulation that commenced in 1968, the PAD has experienced prolonged dry periods in-between floods, accompanied by reduction in the area covered by lakes and ponds that provide habitat for aquatic life. This likely resulted from reduced frequency of formation of major spring ice jams, which are the only mechanism for replenishing the higher-elevation, or “perched”, basins of the PAD. The inundation effectiveness of ice jams depends on the magnitude of the prevailing river flow, but it has not been possible so far to assess whether regulation has had a positive or negative effect on breakup flows. Using a comprehensive BC Hydro data set, containing river inflows up to the W.A.C. Bennet Dam, “naturalized” breakup flows are computed; these are flows that would have occurred under natural flow conditions and are tabulated for each year of the study period (1972–2016). The rigour and utility of the adopted “lagged-flow” methodology are demonstrated via basic hydrodynamic principles and comparisons with independently generated numerical-modelling data for an early portion of the regulation period. Though there can be significant differences between naturalized and regulated flows in individual years, average flow during the first week of May, the typical time when major ice jams form, has not been affected by regulation. During the last week of April and the second week of May, regulation has respectively had a positive and negative effect on average flow. Naturalized flows exhibit practically no temporal trend in the study period (1972–2016), while regulated flows exhibit decreasing, but not statistically significant (P-value > 0.05), trends. It is shown further that the time when the regulated spring outflow begins to be curtailed can be a key factor in Peace River flow conditions near the PAD.

Extensive high-latitude regions, such as northern deltaic ecosystems, are challenging to access due to remoteness and cold conditions during extended periods of the year. The hydro-ecological state of shallow water ecosystems can be influenced by anthropogenic activities (e.g., flow regulation, water abstraction) and climate variability/change. Therefore, they need to be monitored to provide baseline and impact data. In this paper, we capitalize on the water - vegetation interaction to evaluate relative water level variations on wetlands of one of the largest inland freshwater deltas in the world between the years 2012 and 2016 by exploiting RADARSAT-2 Synthetic Aperture Radar (SAR) and its differential interferometric configuration (D-InSAR). The influence of different terrain models on the topographic phase correction is also evaluated. Results revealed complex hydrodynamics in the water bodies studied and inferences of environmental processes taking place that modify local landforms and influence water level fluctuations. Comparison between D-InSAR derived water displacements and those measured at specific hydrometric stations indicates overall reliable results. The analysis proposed can be extended to study dynamics of deltaic lakes and wetlands in other areas of the globe.

This review presents a summary of the influences of floods on river ecology, both instream and on the adjacent floodplain, mostly in a Canadian context. It emphasizes that ecological impacts and benefits can be highly dependent on flood-generation processes and their magnitude and timing. In Canada, floods can occur under open-water or ice-influenced river conditions. The ecological impacts of floods generated from ice jamming are particularly relevant in Canadian ecosystems due to the potentially higher water levels produced and suspended sediment concentrations that can be detrimental to instream aquatic habitat, but beneficial to floodplains. Large floods provide a major source of physical disturbance. Moderate floods with shorter return periods can be beneficial to aquatic habitats by providing woody debris that contributes to habitat complexity and diversity, by flushing fine sediments and by providing important food sources from terrestrial origins. Floods also influence water-quality variables such...

This comment paper addresses data and analysis issues in a paper entitled "Streamflow Input to Lake Athabasca, Canada" by Rasouli et al. (2013). Analyses of observed and naturalized lake level data for Lake Athabasca are redone in this comment paper with corrected hydrometric data to provide northerners and researchers with the correct information for environmental assessments. The comment paper also highlights the importance of including in the analysis not only direct inflows to Lake Athabasca, but also the hydraulic influences on lake outflow, especially when meaningful future projections of lake levels are required for water management.

At the beginning of the twenty-first century, the focus of hydrological prediction had been on the development of empirical tools and simulation models that relied heavily on calibration. These pre...