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Wetlands are an integral part of the Canadian landscape, providing crucial ecohydrological services with globally significant benefits. Over the past 75 years, Canadian scientists have emerged as international leaders in wetland hydrological research, contributing to a better understanding of wetland form and function. Early Canadian research was instrumental in the development of a classification scheme that provided a foundation for later investigations into vadose zone processes, solute transport, evapotranspiration, ground-ice dynamics, biogeochemical cycling, and modelling. This work has coalesced into a better understanding of the factors that contribute to wetland presence and persistence on the landscape, and the internal processes that result in their unique functions of carbon sequestration, water storage, flood mitigation, water quality enhancement, and wildlife habitat. In Canada and across the world, wetlands are threatened at a range of scales and intensities by disturbances like climate change, resource extraction, wildfire, altered land use, and contamination. In response, Canadian researchers have become global leaders in characterizing the impacts of disturbance on wetland function and been at the forefront of innovative restoration and reclamation techniques. As the value of wetlandisre increasingly acknowledged by stakeholders and decision-makers, the need for evidence-based wetland research will only continue to grow. Canadian scientists are well-positioned to lead wetland hydrology into the next 75 years. Les milieux humides font partie intégrante du paysage canadien, offrant des services écohydrologiques essentiels avec des avantages d'importance mondiale. Au cours des 75 dernières années, les chercheurs canadiens se sont imposés comme des leaders internationaux dans la recherche hydrologique sur les milieux humides, contribuant à une meilleure compréhension de leur forme et de leur fonction. Les premières recherches canadiennes ont joué un rôle clé dans l'élaboration d'un système de classification qui a servi de fondement à des études ultérieures sur les processus de la zone non saturée, le transport des solutés, l'évapotranspiration, la dynamique de la glace du sol, le cycle biogéochimique et la modélisation. Ces travaux ont mené à une meilleure compréhension des facteurs qui contribuent à la présence et à la durabilité des milieux humides dans le paysage, les processus internes qui donnent lieu à leurs fonctions uniques de séquestration du carbone, de stockage de l'eau, de mitigation des inondations, d'amélioration de la qualité de l'eau, et d'habitats fauniques. Au Canada et partout dans le monde, les milieux humides sont menacés à diverses échelles et intensités par des perturbations telles que le changement climatique, l'extraction de ressources, les feux de forêt, l'utilisation des terres modifiée et la contamination. En réponse, les chercheurs canadiens sont devenus des leaders mondiaux dans la caractérisation des impacts des perturbations sur la fonction des milieux humides et ont été à l'avant-garde de techniques innovantes de restauration et de remise en état. À mesure que la valeur des milieux humides est de plus en plus reconnue par les parties prenantes et les décideurs, le besoin de recherche sur les milieux humides basée sur des preuves ne fera que croître. Les chercheurs canadiens sont bien positionnés pour continuer à diriger la recherche en hydrologie des milieux humides au cours des 75 prochaines années. [ABSTRACT FROM AUTHOR]

In northern Alberta, oil sands mining disturbs the boreal landscape, and reclamation to an 'equivalent land capability' is required. Industry is testing peatland construction as part of landscape reclamation. To determine if constructed peatlands can be self‐sustaining, an understanding of the cycling of solutes in pore water and their interactions with dissolved organic carbon (DOC) is needed since DOC can represent an important carbon loss from peatlands. DOC is of interest due to its biotic origin and use by the microbial community and impact on carbon budgets. Additionally, salinity as a control on DOC quantity and quality may be important in oil sands reclaimed systems due to the likelihood of elevated sodium (Na+) from saline groundwater input derived from tailings used to construct catchments, and natural sources. For this research, DOC concentration and quality, and Na+ concentration were measured in the rooting zone (10 and 30 cm depth) of Nikanotee Fen to evaluate the role of Na+ in DOC dynamics. DOC concentration and quality suggested that DOC in the fen was largely sourced from vegetation inputs, with quality also suggesting increases in vegetation inputs between years. Elevated Na+ at 30 cm below ground surface corresponded with high concentrations of labile DOC. At 10 cm below ground surface, sampling location and temperature were the best predictors of DOC concentration and quality. With expected increases in Na+, increased production of mobile and microbially active DOC may lead to higher rates of carbon export. [ABSTRACT FROM AUTHOR]

Hydrophysical properties of peat influence the partitioning of rainfall into infiltration versus runoff, determine water flow and solute transport patterns, and regulate the carbon and nitrogen cycles in peatlands. Compared with mineral soils, our understanding of hydraulic properties of peat soils is limited, especially of the temporal dynamics of peat properties. A data set of peat subsidence as well as the bulk density (BD) change rate following artificial drainage was assembled from the literature. The collected data cover a time period of up to 272 years of land drainage for forestry and agriculture in boreal and temperate climate zones. The results show that the subsidence rate and BD change rate, and hydrophysical properties of peat can be estimated based on land drainage duration and land use. The most severe shift in pore structure of peat occurs within the first 20 years of land drainage. Peatland drainage reduces macroporosity with pore diameter greater than 50 μm, but increases the volume of pores <5 μm. In the long term, peat thickness loss is responsible for more than 80% of water storage loss. In conclusion, the derived functions between subsidence rate, BD change rate, and drainage duration provide a new approach to estimate the hydrophysical properties of peat (pore structure, saturated hydraulic conductivity, specific yield, and soil water storage) on a centennial scale. The derived hydrophysical parameter values can be used for long‐term hydrological modeling, especially if measured hydraulic parameters of peat are not available. Key Points: Peatland subsidence and hydrophysical properties of peat can be estimated based on drainage duration and land usePeatland drainage reduces macroporosity but increases the volume of pores <5 μmPeat thickness loss is responsible for more than 80% of water storage loss [ABSTRACT FROM AUTHOR]

Mine reclamation requires the reconstruction of entire landforms and drainage systems. The hydrological regime of reclaimed landscapes will be a manifestation of the processes operating within the individual landforms that comprise it. Hydrology is the most important process regulating wetland function and development, via strong controls on chemical and biotic processes. Accordingly, this research addresses the growing and immediate need to understand the hydrological processes that operate within reconstructed landscapes following resource extraction. In this study, the function of a constructed fen watershed (the Nikanotee Fen watershed) is evaluated for the first two years following construction (2013–2014) and is assessed and discussed within the context of the construction-level design. The system design was capable of sustaining wet conditions within the Nikanotee Fen during the snow-free period in 2013 and 2014, with persistent ponded water in some areas. Evapotranspiration dominated the water fluxes from the system. These losses were partially offset by groundwater discharge from the upland aquifer, which demonstrated strong hydrologic connectivity with the fen in spite of most construction materials having lower than targeted saturated hydraulic conductivities. However, the variable surface infiltration rates and thick placement of a soil-capping layer constrained recharge to the upland aquifer, which remained below designed water contents in much of the upland. These findings indicate that it is possible to engineer the landscape to accommodate the hydrological functions of a fen peatland following surface oil sands extraction. Future research priorities should include understanding the storage and release of water within coarse-grained reclaimed landforms as well as evaluating the relative importance of external water sources and internal water conservation mechanisms for the viability of fen ecosystems over the longer-term. [ABSTRACT FROM AUTHOR]

In Canada, peatlands are the most common type of wetland, but boundary delineation in peatland complexes has received little attention in the scientific literature. Typically, peatland boundaries are mapped as crisp, absolute features, and the transitional lagg zone-the ecotone found between a raised bog and the surrounding mineral land-is often overlooked. In this study, we aim (1) to advance existing approaches for detecting and locating laggs and lagg boundaries using airborne LiDAR surveys and (2) to describe the spatial distribution of laggs around raised bog peatlands. Two contrasting spatial analytical approaches for lagg detection were tested using five LiDAR-derived topographic and vegetation indices: topography, vegetation height, topographic wetness index, the standard deviation of the vegetation's height (as a proxy for the complexity of the vegetation's structure), and local indices of elevation variance. Using a dissimilarity approach (edge-detection, split-moving window analysis), no one variable accurately depicted both the lagg-mineral land and bog-lagg boundaries. Some indicators were better at predicting the bog-lagg boundary (i.e., vegetation height) and others at finding the lagg-mineral land boundary (i.e., topography). Dissimilarity analysis reinforces the usefulness of derived variables (e.g., wetness indices) in locating laggs, especially for those with weak topographic and vegetation gradients. When the lagg was confined between the bog and the adjacent upland, it took a linear form, parallel to the peatland's edge and was easier to predict. When the adjacent mineral land was flat or sloping away from the peatland, the lagg was discontinuous and intermittent and more difficult to predict. [ABSTRACT FROM AUTHOR]

Peatland development occurs naturally over long periods of time in response to climate, geology, hydrology and vegetation. Open-pit oil sands mining activities in Northern Alberta result in large-scale removal of the surficial landscape, which comprises many (~ 50%) peatlands, approximately 90% of which are fens with a wide range of peat thicknesses (< 1 m to ~ 5 m). Recently, the concept of peatland creation was adapted into the regulatory framework. Two experimental fen peatlands have now been constructed on post-mining landscapes in order to test the design implications and implementation methods and to develop knowledge to advance the concept. These two systems were guided by different conceptual approaches: one utilized numerical modelling for landscape optimization, while the other attempted to mimic the landscape position of natural fen systems (and supported the design with numerical modelling). Both system designs attempt to accelerate succession by adding peat substrate (0.5 m and 2 m) and revegetating, with the belief that the system will stabilize within decades as opposed to millennia. This paper provides an overview of the feasibility of peatland creation, from a primarily hydrologic perspective, and addresses the complexity of determining whether these projects can be deemed a success. Future landscape design plans could benefit from a change of perception of the role of peatlands in the landscape. This change should involve a shift away from viewing wetlands as landforms constrained to low-lying areas within the reclaimed landscape, and towards recognizing that peatlands can function as both a sink and source of water to the remainder of the catchment. Wetland interconnectivity within the reconstructed landscape could increase water detention and storage during wet periods, which would benefit both the wetlands and the forestlands during dry periods. The assessment of the success of these constructed systems should be a reflection of our ability to correctly and accurately predict the influence of external forcings (e.g., climate) on the processes operating within a newly constructed system. Short timeframes (~ 5 years) are sufficient to characterize a range of processes operating in the constructed ecosystems; however, longer time periods will reduce uncertainty in the assessment of the system's successional pathway. The design of future constructed fen peatlands must employ an adaptive approach that assimilates the knowledge developed in the current research and the information attained over the longer-term to guide the design of future fen systems. [ABSTRACT FROM AUTHOR]

Abstract: Peatlands abandoned after being exploited for horticultural materials can be characterized by soil–water deficits that challenge the establishment of appropriate plant species, thus rewetting is an important step to restoring them to naturally functioning ecosystems. A bog section of Bic-Saint-Fabien peatland near Rimouski, QC was vacuum-harvested for peat production and abandoned in 2000. Harvesting activity left topographic elevation differences across the harvested area, creating wetness gradients. In general, the site interior had more available water than peripheral regions. Bic-Saint-Fabien was cut down to minerotrophic sedge peat; therefore it was restored as a fen. Research for this study lasted four years, 2008–2011. A water budget was created for every year of study to determine the importance of different hydrological parameters at Bic-Saint-Fabien. The main loss of water was through evapotranspiration and the principal input was precipitation. The main difference in the water budget between study years was that pre-rewetting was climatologically wetter than post-rewetting. Despite more available water before rewetting, before-after-control-impact design ANOVA indicated the water table was significantly higher at the cutover area after rewetting. In 2011 a wetness gradient remained evident within the cutover section of the peatland; however the mean seasonal water table was close (within 20cm) to the peat surface at all measured wells. An interior section of Bic-Saint-Fabien remained saturated for nearly all of 2011 and had mean seasonal water table of +2.4cm, and volumetric soil moisture content and soil water pressure, measured 5cm below the surface, of 86% and +4mbar, respectively, compared to −15.4cm, 67% and −13mbar, respectively, at a nearby (∼100m) peripheral section. Systematic differences in wetness across the site suggest that a uniform prescription for vegetation re-establishment in the rewetted section may not be appropriate. [Copyright &y& Elsevier]

Abstract: Restoration measures (ditch blocking, bund construction, etc.) were applied to a cutover part of the Bois-des-Bel (BdB) bog peatland in autumn 1999; since then a near complete cover of Sphagnum rubellum (∼15cm) has developed over the old cutover peat, along with a suite of bog vegetation. This research assesses the restored site''s (RES) hydrological condition after 10 growing seasons (May 15th–August 15th, 2010) through comparison with an adjacent unrestored site (UNR) and a natural site (NAT) located elsewhere in the peatland. Evapotranspiration (ET) from RES (242mm) has not noticeably changed since the first 3 years post-restoration (2000–2002) still maintaining lower ET rates than UNR (290mm). The highest ET occurred at NAT (329mm), dissimilar to RES despite similar vegetation cover. UNR generates more runoff (37mm) than RES (7mm), similar to the initial assessments. However, since the initial assessments the average water table has continued to rise, from −35.3 (±6.2)cm (2000–2002) to −27.3 (±14.9)cm (2010) below the cutover peat surface but still fluctuates predominantly within the cutover peat and not the regenerated Sphagnum. The regenerated Sphagnum at RES has increased the surface elevation by ∼15–20cm, and with respect to its surface the average water table was at ∼−42.3 (±20.9)cm. However, its water table was still lower (and more variable) than at NAT (33.2±9.0cm), with respect to the moss surface. Average soil water pressures in 2010 were similar to the early post-restoration condition at depths of 10cm (−43.0±12.2 and −44.1±13.1mb) and 20cm (−41.4±13.0 and −40.6±10.5mb) below the cutover surface at RES and UNR, respectively. Volumetric soil moisture contents (θ) at 2.5, 7.5 and 17.5cm depths were higher in the Sphagnum moss at NAT (0.23, 0.31, and 0.71) compared to RES (0.12, 0.11, and 0.23), where the underlying cutover peat had a relatively high θ of 0.74. The low moisture content in the new moss overlying the relatively moist cutover peat indicates there was restricted connectivity between the two layers. Ten years following the implementation of restoration measures and the development of a near complete 15cm thick Sphagnum moss layer, further time is required for the moss layer to develop (increase in thickness and bulk density, hence water retention capacity) and more consistently host the water table, so that the average water content more closely mimics NAT. [Copyright &y& Elsevier]

Snow distribution, ablation and snowmelt energy balance components were characterized in a vacuum harvested and an adjacent undisturbed forested section of a peatland during the 2009 snowmelt period to determine snow distribution and melt dynamics on a previously harvested peatland, since abandoned and partly revegetated. The forested peatland had the deepest snowpack at 121 cm, particularly along the edge of the forested section adjacent to the more windblown previously harvested peatland. The snowpack density was greatest in the harvested peatland, which was subject to greater wind compaction and mid-winter melt-refreeze episodes; however, snow water equivalence was higher in the forested peatland. Radiative fluxes dominated the snowmelt energy balance. Increased canopy cover within the forested peatland restricted incident radiation and delayed melt, whereas melt rates were rapid across the harvested peatland, driven by higher radiant and turbulent fluxes. Ablation calculated using a simple, one-dimensional model showed good temporal agreement with the observed ablation trends except when standing melt water pooled on the surface of the harvested section, causing more rapid modelled melt rates than observed. The shallower snowpack and more rapid melt across the harvested peatland limited the amount of melt water that was available for spring recharge. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Extraction of oil sands in the relatively dry Western Boreal Plains near Fort McMurray, Alberta, destroys the natural surface cover including fen peatlands that cover upto 65% of the landscape. Industry and environmental monitoring agencies have questioned the ability to reclaim fen peatlands in the post-mine landscape. This study proposes a conceptual model to replace fen systems with fen peat materials supported by groundwater inflow from a constructed watershed. A numerical model is used to determine the optimum system geometry, including the ratio of upland to fen area, thickness and slope of sand materials, and thickness of peat and of the liner that would result in flows that sustain peat wetness to a critical threshold soil water pressure of -100 cm of water at a peat depth of 10 cm. We also test the sensitivity of the system to variations in the value and spatial configuration of the hydraulic conductivity (K) of locally available materials. The optimal conditions were achieved using an upland area at least twice that of the fen, underlain by a sloping (3%) layer of fine-grained material with hydraulic conductivity (K) of 10-10 m/s, that maintains lateral groundwater flow in a sand layer with K of 10-4 to 10-5 m/s. Using daily climate inputs that included 1998, the driest summer on record, the model suggests that adequate wetness can be sustained in the fen for the growing season, and that the extent of water table recession was similar to undisturbed systems during that period. [ABSTRACT FROM AUTHOR]

The proposed harvesting of previously undeveloped forests in north coastal British Columbia requires an understanding of hydrological responses. Hydrometric and isotopic techniques were used to examine the hydrological linkages between meteoric inputs to the surface-groundwater system and runoff response patterns of a forest-peatland complex. Quickflow accounted for 72-91% of peak storm discharge. The runoff ratio was lowest for open peatland areas with thick organic horizons (0.02-0.05) due to low topographic gradients and many surface depressions capable of retaining surface water. Runoff ratio increased comparatively for ephemeral surface seep flows (0.06-0.40) and was greatest in steeply sloping forest communities with more permeable soils (0.33-0.69). The dominant mechanism for runoff generation was saturated shallow subsurface flow. Groundwater fluxes from the organic horizon of seeps (1.70-1.72 m³ day-1 m-1) were an important component of quickflow. The homogeneous δ²H–δ18O composition of groundwater indicated attenuation of the seasonal rainfall signal by mixing during recharge. The positive correlation (r² = 0.64 and 038, α = 0.05) between slope index and δ18O values in groundwater suggests that the spatial pattern in the δ18O composition along the forest-peatland complex is influenced by topography and provides evidence that topographic indices may be used to predict groundwater residence time. [ABSTRACT FROM AUTHOR]

Measurements of micrometeorological variables were made for two snow-free periods at a Restored vacuum harvested and non-restored (Comparison) section of a peatland in eastern Québec, Canada. Measurements of evapotranspiration and surface heat fluxes were obtained using an eddy correlation energy balance system at the Restored site and a combination Priestley–Taylor and lysimeter approach at the Comparison site. At the ecosystem scale, the energy, water and gas exchange processes are strongly coupled. Through harvesting, a peatland may lose most of its surface vegetation cover, altering the thermal regime of the peat, while the drier conditions required for the harvesting drastically alters the system''s hydrology. The measurements indicate that the adopted restoration practices (blockage of drainage ditches and the spreading of a surface mulch layer) reduce the loss of water from the peat leading to the regrowth of natural vegetation at the Restored site. The Restored site lost approximately 13 and 8% less water to evapotranspiration than the Comparison site in 2000 and 2001, respectively. [Copyright &y& Elsevier]

At the ecosystem scale, the water and gas exchange processes are strongly coupled. Drainage and removal of a peatland's surface vegetation cover for peat harvesting alters its hydrology, and as a direct consequence the carbon budget. Previous studies have measured peatland-atmosphere carbon exchange using the chamber methodology. These studies have indicated that the spatial and temporal variability is large, suggesting the need for continuous ecosystem-scale measurements. This paper presents ecosystem scale measurements of the atmospheric exchange of water and carbon dioxide (CO2) from a restored vacuum-harvested peatland in eastern Québec, Canada, using the eddy correlation measurement approach. Results indicate that the adopted restoration practices reduce the loss of water from the peat. Evapotranspiration from the restored site was 20 and 25% less than that from an adjacent abandoned comparison site in 2000 and 2001 respectively. However, CO2 emissions remain large during non-snow periods (478 and 468 g C m-2 in 2000 and 2001, respectively). The blockage of drainage ditches and the existence of a mulch cover at the site keep the moisture and thermal conditions more or less constant. Consequently, the CO2 flux, which is predominantly soil respiration, is strongly controlled by peat temperature fluctuations. [ABSTRACT FROM AUTHOR]

Post-mine landscape reclamation of the Athabasca Oil Sands Region requires the use of tailings sand, an abundant mine-waste material that often contains large amounts of sodium (Na + ). Due to the mobility of Na + in groundwater and its effects on vegetation, water quality is a concern when incorporating mine waste materials, especially when attempting to construct groundwater-fed peatlands. This research is the first published account of Na + redistribution in groundwater from a constructed tailings sand upland to an adjacent constructed fen peat deposit (Nikanotee Fen). A permeable petroleum coke layer underlying the fen, extending partway into the upland, was important in directing flow and Na + beneath the peat, as designed. Initially, Na + concentration was highest in the tailings sand (average of 232 mg L −1 ) and lowest in fen peat (96 mg L −1 ). Precipitation-driven recharge to the upland controlled the mass flux of Na from upland to fen, which ranged from 2 to 13 tons Na + per year. The mass flux was highest in the driest summer, in part from dry-period flowpaths that direct groundwater with higher concentrations of Na + into the coke layer, and in part because of the high evapotranspiration loss from the fen in dry periods, which induces upward water flow. With the estimated flux rates of 336 mm yr −1 , the Na + arrival time to the fen surface was estimated to be between 4 and 11 years. Over the four-year study, average Na + concentrations within the fen rooting zone increased from 87 to 200 mg L −1 , and in the tailings sand decreased to 196 mg L −1 . The planting of more salt-tolerant vegetation in the fen is recommended, given the potential for Na + accumulation. This study shows reclamation designs can use layered flow system to control the rate, pattern, and timing of solute interactions with surface soil systems. [ABSTRACT FROM AUTHOR]

Early attempts at peatland restoration have been aimed mostly at rewetting the peat, which alone has proven inadequate to ensure good regeneration of Sphagnum mosses. Sphagnum mosses can be actively reintroduced by scattering Sphagnum fragments (diaspores) on bare peat surfaces and by sheltering them against desiccation. The present study aims at refining the restoration techniques to reintroduce Sphagnum where the surface conditions of cutover peatlands are too harsh for natural Sphagnum establishment. The objective is to increase local moisture conditions of the peat by reprofiling the surface to invert the camber created during drainage operations. Sphagnum diaspores were spread in the concavity. Reprofiling fields increased Sphagnum establishment compared to control sites. The addition of two plastic sheets on the edge of the field reduced evaporation and directed precipitation towards the middle of the field. When they were combined with reprofiling, there was a further increase in the establishment success of Sphagnum. [ABSTRACT FROM AUTHOR]

[Display omitted] • Restored peatlands can be drier than natural peatlands due to a capillary barrier effect. • In-field compression is a novel technique to reduce the capillary barrier effect. • Compression alters the moss structure lowering the proportion of large pores. • Bulk density and water retention increase with compression. • Compression increases Sphagnum moss resilience to drying. The restoration and subsequent regeneration of Sphagnum moss on harvested peatlands can result in poor hydrological connectivity between the regenerated Sphagnum moss and the remnant cutover peat due to the formation of a capillary barrier that favours retention of water in the underlying cutover peat. In a restored cutover peatland in Québec, Canada, this resulted in a lower soil water content of the regenerated Sphagnum moss compared to a natural analogue, which may limit carbon sequestration potential. Previous work has shown it may take > 40 years for the regenerated moss layer to overcome this capillary barrier effect, however mechanical compression may provide a novel restoration technique to weaken the capillary barrier in restored peatlands. This study evaluated the effectiveness of field-based mechanical compression to ameliorate the capillary barrier effect and increase the moisture content in a restored cutover peatland. A section of restored Bois-des-Bel peatland was compressed using a John Deere 6430 series tractor in January 2016, followed by hydrological monitoring May-August. The Compressed site was compared to a nearby Uncompressed site, and a natural peatland ∼ 2 km away, to determine relative success of mechanical compression. The compression reduced moss height by 48%, increasing bulk density by 37% and reducing the proportion of macropores by 15% throughout the moss layer. Consequently, compression increased soil water retention and average soil moisture content at the Compressed site was consistently higher throughout the moss profile than in the Uncompressed site. This increased the resilience of the moss to drying, though the degree of increased resilience is unknown. Despite not having the same hydrophysical properties of the Natural site, the Compressed site was wetter than the Uncompressed site due to the lessening of the capillary barrier effect and moving the surface closer to the water table, thus decreasing the water stress of the regenerated Sphagnum carpet. [ABSTRACT FROM AUTHOR]