> 50 % of Canada's landmass is underlain by perennially frozen ground (permafrost). These permafrost regions are changing rapidly in response to a warming climate, with Canada's arctic warming at a rate > 3 times higher than global average. As permafrost distribution shifts in response to this warming, it alters the water cycle, affecting both water quantity and water quality. However, large-scale hydrological models that integrate climate change impacts often lack permafrost representation. The Carcajou Regional Model Dataset contains the inputs needed to construct a standalone groundwater model or a fully integrated groundwater - surface water model of the Carcajou watershed in the Northwest Territories, Canada, a zone of transition between continuous permafrost and discontinuous permafrost. The three-dimensional geological data was created by refining national-scale mapping products, with local-scale data. Land cover, topography, and surface water flow were generated from national scale mapping products. Climate forcing data for the period from 2010 to 2016 was generated based national scale historical products. The proper approach to representing permafrost in large-scale hydrological models is largely undefined, with no consensus on conceptualization or parameterization. This dataset allows researchers to rapidly test new approaches to permafrost representation, without the need for additional data collection. The data set includes long term surface water discharge records to assess model performance and compare representations. The data set can be further adapted to simulate projected permafrost distribution scenarios and be used to forecast the effect of permafrost change on water quantity.

Improving understanding of how water use efficiency (WUE), evapotranspiration (ET), and gross primary productivity (GPP) (CO2 exchange) vary across agricultural systems can help farmers better prepare for an uncertain future due to climate change by assessing water requirements for a crop as a function of current environmental conditions. This study: (a) quantified field-scale plant-water-carbon dynamics for silage maize (Zea mays L.) and alfalfa (Medicago sativa L.) crops - two dominant forage crops in southern Ontario, Canada; and (b) identified differences in plant carbon-water dynamics between these two crops, relating these differences to vegetation-driven ecosystem controls. Climate and soil properties were similar between the two study sites, and water availability was not limiting, suggesting that the overall temporal differences in carbon-water relations were driven by vegetation differences, mainly crop choice and management practices. Alfalfa had greater seasonal GPP, ET, and WUE than maize, due to a longer growing season. Differences in daily WUE between maize and alfalfa were driven by differences in GPP rather than ET. Multiple harvests reduced leaf-aging effects and promoted periods of rapid growth in alfalfa. In contrast, late seedling emergence and self-shading reduced GPP in maize. Under a warmer future climate, crop selection (i.e., perennial vs. annual), harvest regimes, and changes in growing season length should be considered when trying to manage for increased WUE. However, longer duration studies to validate these results are required to better address the impacts of climatic variability-especially antecedent conditions-to better inform future crop choices within a climate change context.

In northern peatlands, near‐saturated surface conditions promote valuable ecosystem services such as carbon storage and drinking water provision. Peat saturated hydraulic conductivity ( K sat ) plays an important role in maintaining wet surface conditions by moderating drainage and evapotranspiration. Peat K sat can exhibit intense spatial variability in three dimensions and can change rapidly in response to disturbance. The development of skillful predictive equations for peat K sat and other hydraulic properties, akin to mineral soil pedotransfer functions, remains a subject of ongoing research. We report a meta‐analysis of 2,507 northern peat samples, from which we developed linear models that predict peat K sat from other variables, including depth, dry bulk density, von Post score (degree of humification), and categorical information such as surface microform type and peatland trophic type (e.g., bog and fen). Peat K sat decreases strongly with increasing depth, dry bulk density, and humification; and increases along the trophic gradient from bog to fen peat. Dry bulk density and humification are particularly important predictors and increase model skill greatly; our best model, which includes these variables, has a cross‐validated r 2 of 0.75 and little bias. A second model that includes humification but omits dry bulk density, intended for rapid field estimations of K sat , also performs well (cross‐validated r 2 = 0.64). Two additional models that omit several predictors perform less well (cross‐validated r 2 ∼ 0.5), and exhibit greater bias, but allow K sat to be estimated from less comprehensive data. Our models allow improved estimation of peat K sat from simpler, cheaper measurements.

At the Nikanotee Fen Watershed, a pioneering reclamation project in the Athabasca Oil Sands Region, elevated sodium (Na+) in the porewater of mine-waste materials has been shown to migrate to the fen through groundwater, likely influencing fen vegetation health. Given the potential of Na+ to steer the ecological development of the fen, the goal of this research is to quantify the spatial distribution of Na+ and to characterize the Na+ mass balance of the surface and shallow subsurface of the fen. For a given time, the highest Na+ concentrations were generally found in the wettest part of the fen in the southwestern corner, and the lowest in the relatively dry northeast corner near the drainage outlet. Na+ concentrations in ponded surface water were responsive to rainfall-induced dilution and evapoconcentration, whereas porewater salinity in shallow groundwater was insensitive to meteorological conditions. Surface discharge controlled the mass efflux of Na+ from the system at an estimated average rate of 4 kg∙day−1 between June and August. Given the relatively small proportion of salt being flushed annually, and the greater rate of mass inflow relative to export, elevated salinity will likely be sustained for several decades. Since elevated Na+ concentrations are impacting the rooting zone of vegetation and have exceeded the salinity stress-threshold of mosses, targeting salt-tolerant vegetation will be important to maintain carbon accumulation in constructed systems.

Millions of tonnes of coarse tailings sand are produced every year as a byproduct of the bitumen extraction process in the Athabasca Oil Sands Region. These tailings materials contain residual quantities of mobile solutes, which can be transported through groundwater to downgradient terrestrial and aquatic ecosystems. The anticipated ubiquity of coarse tailings sand on the post-mined landscape necessitates the characterization of its hydraulic and transport properties. Hydraulic conductivity and dispersivity was evaluated at multiple scales, and included the first field-scale tracer test conducted in a tailings sand aquifer. Average hydraulic conductivity derived using laboratory cores, single-well response tests, and the tracer test were 3.2 m d(-1), 2.9 m d(-1), and 3.4 m d(-1), respectively. These measurements demonstrated close agreement and were consistent with expectations of a material that experiences some grain-size segregation and homogenization due to the oil sands process and the nature of deposition. The field-scale tracer test appeared to obtain the asymptotic dispersivity of the coarse tailings sand aquifer, reaching a maximum value of 0.5 m after 18 m of displacement. Coarse tailings in the oil sands that experience similar processes of segregation, settling, and deposition on the reclamation landscape could be expected to have similar hydraulic properties.

Peatlands dominate the landscape (similar to 50% of total area) in the Athabasca Oil Sands Region (AOSR) in northern Alberta, and as such, are susceptible to hydrological disturbance from oil sands mining and exploration. In this study, we explore the hydrochemical response of a disturbed fen (Firebag Fen) in the AOSR following the removal of a temporary access road that was operational from 2007 to 2013. Prior to road removal flow was impeded at Firebag Fen, evidenced by inundation on the up-gradient side, and a lower water table on the down-gradient side of the road. Reclamation included the road removal of the similar to 0.5 m thick road, including 0.15 m of clay, 0.3 m of mud and organics, and 0.05 m of gravel, which left a surficial depression following removal. Peat samples (n = 139) collected immediately following road removal demonstrated significantly greater bulk densities on the down-gradient side relative to the up-gradient side of the fen, and in the road-removed area relative to up- and down-gradient areas. These combined changes decreased the average hydraulic conductivity of the fen by similar to 79%, which reduced water discharge across the site. Another peat sampling campaign in 2016 (n = 48), three years after removal, showed a significant decrease in bulk density where the road was removed, to within the range of values observed at areas up and down-gradient of the road. These changes increased the average hydraulic conductivity of the entire system by 64%, compared to that which was measured in 2013, with water discharge 9 and 12% higher than in 2013, during characteristically dry and wet periods, respectively. Some changes to the water chemistry (n = 24-28 for each sampling date) of the fen were also detected but patterns were different among parameters measured. For example, median concentrations on the down-gradient side of the road were 1651% (NO3-), 280% (SO42-) and 135% (Cl-) higher relative to the up-gradient side of the road. Over time following road removal, differences were reduced to 100% for nitrate, 192% for sulphate, 108% for chloride, while other parameters remained relatively unchanged (Ca2+, Mg2+, K-). Continued peat rebound (thus increasing hydraulic conductivity) may occur over time; however, elucidating this would require long-term monitoring. It is concluded that despite the impacts that were caused to the site, the natural hydrologic regime of the fen was able to operate following removal. Removal and reclamation should be considered as a worthwhile venture for roads that extend through fens and are no longer in use.

Study region: A peatland watershed was constructed on a post-mined oil sands lease in Northern Alberta, Canada, with the intention of replicating the function of natural wetlands removed by surface mining. Study focus: Given the potential for moisture limited conditions due to the sub-humid regional climate, ensuring sufficient water availability in these landscapes is a principal concern. This research demonstrates how small recharge basins can modify the hydrology to promote groundwater recharge critical for sustaining saturated conditions in a downgradient wetland. New hydrological insights for the region: Location was important in determining the efficacy of recharge basins. Specifically, basins placed at the confluence of two hillslopes detained substantial volumes of runoff due to large upslope areas, contributing similar to 30% of the groundwater budget to the fen, while only occupying 1% of the upland area. Basins situated near low relief hillslopes or altogether isolated from a hillslope did not detain appreciable runoff and therefore had a minor role in recharging groundwater. Groundwater in the vicinity and downgradient of active recharge basins had considerably lower solute concentrations because of dilution. This suggests that basins can not only enhance recharge within engineered landscapes, providing a consistent and focused supply of water to upland aquifers, but offer relatively fresh groundwater to downgradient ecosystems. This could ameliorate the impact of high salinity present in oil sands process-affected materials.

Ecosystem water-use efficiency (WUE), a ratio between gross ecosystem production (GEP) and water loss through evapotranspiration (ET) can be helpful for the assessment of coupled peatland carbon and water cycles under anthropogenic changes in the Athabasca oil sands region (AOSR) where extensive oil sands development has been occurring since the 1960's. As such, this study assessed multiyear peak growing season variability of WUE at four fens (poor treed, poor open, treed moderate-rich, open saline) near Fort McMurray using the eddy covariance technique combined with a set of environmental variables. Freshwater fens were characterized by WUE values within the range reported from other boreal wetlands while a saline fen had significantly lower values of WUE. Negative correlation (R-s < -0.55, p < 0.05) between WUE and net radiation was observed. Moisture conditions were responsible for interannual differences in WUE, whereby increasing WUE under wetter conditions was observed. However, such a pattern was offset by decreased air temperature (T-air) resulting in moisture oversupply. This study also revealed a negative effect of wildfire on WUE due to a prominent decline in GEP and a moderate decrease in ET. WUE can be useful for monitoring the functioning of natural and constructed fens, but a better understanding of WUE variability under a wide range of climatic conditions with respect to differences in vegetation is required.

Oil sands development within the Athabasca Oil Sands Region (AOSR) has accelerated in recent decades, causing alteration to natural ecosystems including wetlands that perform many vital ecosystem functions such as water and carbon storage. These wetlands comprise more than half of the landscape, and their distribution and local hydrology are the result of interactions among a subhumid climate, topography, and spatially heterogeneous surficial and bedrock geology. Since hydrology plays a fundamental role in wetland ecological functioning and determines wetland sensitivity to human disturbances, the characterization of anthropogenic impacts on wetland hydrology in the AOSR is necessary to assess wetland resilience and to improve current best management practices. As such, this paper reviews the impacts of oil sands development and related disturbances including infrastructure construction, gravel extraction, and land clearing on wetland function in the AOSR. Hydrologic disturbances in wetlands in the AOSR include changes to soil hydrophysical properties that control water table position, the interruption of recharge–discharge patterns, and alteration of micrometeorological conditions; these in turn govern wetland ecological structure and wetland ecosystem processes (e.g., evapotranspiration, nutrient cycling). Given that anthropogenic disturbance can affect natural wetland succession, long-term hydrological monitoring is crucial for predicting the response of these ecosystems to varying levels of human impact.

Current efforts to assess changes to the wetland hydrology caused by growing anthropogenic pressures in the Athabasca Oil Sands Region (AOSR) require well‐founded spatial and temporal estimates of actual evapotranspiration (ET), which is the dominant component of the water budget in this region. This study assessed growing season (May–September) and peak growing season (July) ET variability at a treed moderate‐rich fen and treed poor fen (in 2013–2018), open poor fen (in 2011–2014), and saline fen (in 2015–2018) using eddy covariance technique and a set of complementary environmental data. Seasonal fluctuations in ET were positively related to net radiation, air temperature and vapour pressure deficit and followed trends typical for the Boreal Plains (BP) and AOSR with highest rates in June–July. However, no strong effect of water table position on ET was found. Strong surface control on ET is evident from lower ET values than potential evapotranspiration (PET); the lowest ET/PET was observed at saline fen, followed by open fen, moderately treed fen, and heavily treed fen, suggesting a strong influence of vegetation on water loss. In most years PET exceeded precipitation (P), and positive relations between P/PET and ET were observed with the highest July ET rates occurring under P/PET ~1. However, during months with P/PET > 1, increased P/PET was associated with decreased July ET. With respect to 30‐year mean values of air temperature and P in the area, both dry and wet, cool and warm growing seasons (GS) were observed. No clear trends between ET values and GS wetness/coldness were found, but all wet GS were characterized by peak growing seasons with high daily ET variability.

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 232mgL−1) and lowest in fen peat (96mgL−1). Precipitation-driven recharge to the upland controlled the mass flux of Na from upland to fen, which ranged from 2 to 13tons 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 336mmyr−1, the Na+ arrival time to the fen surface was estimated to be between 4 and 11years. Over the four-year study, average Na+ concentrations within the fen rooting zone increased from 87 to 200mgL−1, and in the tailings sand decreased to 196mgL−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.

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.