Sean K. Carey

The role of soil pipes as a slope runoff mechanism, Subarctic Yukon, Canada

Pipeflow in subarctic slopes provides a preferential runoff mechanism that bypasses the soil matrix, rapidly conveying water to the stream. Extensive soil piping occurs in the central Wolf Creek basin, Yukon, at the interface of the organic and mineral horizons. Flow in these pipes are ephemeral, transmitting water only when the water table is within or above the zone where pipes occur. During snowmelt, pipeflow began several days after the onset of surface runoff. Pipeflow contribution increased until ground thaw lowered the water tables, leaving matrix flow within the organic layer as the dominant mode of runoff. Pipeflow accounted for 21% of runoff during the 15 day melt period of 1997. Following melt, pipeflow recurred only during two intense summer rainstorms, each yielding different pipeflow response characteristics. During melt, pipeflow closely followed the daily snowmelt cycles and responded earlier than the integrated slope runoff. In the summer, pipeflow hydrographs rose and fell much quicker than direct storm runoff from the entire slope, which was dominated by fast matrix flow within the organic layer. Pipeflow contributing areas were relatively small, but their extent changed with hillslope wetness. Analysis revealed that the Manning flow formula can be combined with contributing areas to simulate pipeflow discharges. Unlike temperate environments where frozen ground is not a factor, the frost table position significantly controls the position of the phreatic surface, and must be considered in any models of pipeflow in permafrost slopes.

Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire: an expert assessment

As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release w ...

Hydrology of Two Slopes in Subarctic Yukon, Canada

Two subarctic forested slopes in central Wolf Creek basin, Yukon, were studied in 1996–1997 to determine the seasonal pattern of the hydrologic processes. A south-facing slope has a dense aspen forest on silty soils with seasonal frost only and a north-facing slope has open stands of black spruce and an organic layer on top of clay sediments with permafrost. Snowmelt is advanced by approximately one month on the south-facing slope due to greater radiation receipt. Meltwater infiltrates its seasonally frozen soil with low ice content, recharging the soil moisture reservoir but yielding no lateral surface or subsurface flow. Summer evaporation depletes this recharged moisture and any additional rainfall input, at the expense of surface or subsurface flow. The north-facing slope with an ice rich substrate hinders deep percolation. Snow meltwater is impounded within the organic layer to produce surface runoff in rills and gullies, and subsurface flow along pipes and within the matrix of the organic soil. During the summer, most subsurface flows are confined to the organic layer which has hydraulic conductivities orders of magnitudes larger than the underlying boulder-clay. Evaporation on the north-facing slope declines as both the frost table and the water table descend in the summer. A water balance of the two slopes demonstrates that vertical processes of infiltration and evaporation dominate moisture exchanges on the south-facing slope, whereas the retardation of deep drainage by frost and by clayey soil on the permafrost slope promotes a strong lateral flow component, principally within the organic layer. These results have the important implication that permafrost slopes and organic horizons are the principal controls on streamflow generation in subarctic catchments. Copyright

Inferring groundwater contributions and pathways to streamflow during snowmelt over multiple years in a discontinuous permafrost subarctic environment (Yukon, Canada)

Research on large northern rivers suggests that as permafrost thaws, deeper groundwater flowpaths become active, resulting in greater baseflow, increased concentrations of weathering ions and reduced concentrations of dissolved organic carbon in the streamflow. In contrast, at the headwater-catchment scale, where understanding of groundwater/surface-water interactions is developed, inter-annual variability in climate and hydrology result in complex hydrological and chemical responses to change. This paper reports on a 4-year runoff investigation in an alpine discontinuous permafrost environment in Yukon, Canada, using stable isotopes, major dissolved ions and hydrometric data, to provide enhanced insight into the inter-annual-variability runoff-generation processes. Stable isotope results suggest that pre-event (old) water stored within the catchment dominates the snowmelt hydrograph, and dissolved ion results reveal that groundwater pathways occur predominantly in the near-surface during freshet. Dissolved organic carbon varies inter-annually, reflecting changing melt patterns, whereas weathering ions generated from deeper flowpaths become diluted. The total snow-water equivalent does not have a major influence on the fraction of snowmelt water reaching the stream or the runoff ratio. Results from multiple years highlight the considerable variability over short time scales, limiting our ability to detect climate-change influences on groundwater at the headwater scale.RésuméLa recherche sur des grandes rivières du Nord suggère que, lorsque le permafrost fond, des chenaux d’écoulement profonds deviennent actifs, ce dont il résulte un plus grand écoulement de base, des augmentations des concentrations en ions d’altération météorique et une réduction des concentrations en carbone organique dans le flux d’écoulement. Par contraste, à l’échelle de tête de bassin versant, où la compréhension des interactions eau de nappe/eau de surface a été développée, la variabilité inter-annuelle du climat et de l’hydrologie a pour résultat des réponses complexes hydrologiques et chimiques au changement. Cet article rapporte une investigation s’étendant sur quatre ans dans une environnement de typa alpin au Yukon, Canada, utilisant des isotopes stables, les ions majeurs en solution et des données hydrométriques, fournissant une idée affinée de la variabilité interannuelle des processus d’écoulement. Les résultats fournis par les isotopes stables suggèrent que de l’eau anciennement accumulée dans le basin versant domine l’hydrographe de la neige fondue, et les ions en solution révèlent que les chenaux d’écoulement de l’eau de nappe s’établissent de façon prédominante en sub-surface durant la crue. Le carbone organique dissout varie de façon interannuelle, reflétant les variations de conditions de fusion, alors que les ions d’altération générés par les écoulements plus profonds se trouvent dilués. L’équivalent total eau de neige n’a pas une influence majeure sur la fraction d’eau de fusion de neige atteignant le chenal d’écoulement ou sur le ratio découlement. Les résultats de nombreuses années mettent en lumière la variabilité considérable sur des petites échelles de temps, limitant notre capacité de détecter des influences de changement climatique sur l’eau de nappe à l’échelle du bassin versant.ResumenLa investigación en grandes ríos del norte sugiere que a medida que se deshielan los permafrost, las trayectorias de flujo de aguas subterráneas más profundas se activan, resultado de un mayor flujo de base, concentraciones incrementadas de iones meteorizados y concentraciones reducidas en el carbono orgánico disuelto en la corriente. En contraste, a escala de cabeceras de las cuencas, donde se desarrolla el entendimiento de las interacciones agua superficial / subterránea, la variabilidad interanual en el clima y la hidrología da como resultado respuestas hidrológicas y químicas complejas al cambio. Este trabajo informa una investigación de cuatro años del escurrimiento superficial en un ambiente alpino discontinuo de permafrost en Yukon, Canada, usando isótopos estables, iones disueltos mayoritarios y datos hidrométricos, para proporcionar un conocimiento más profundo en la variabilidad interanual de los procesos que genera el escurrimiento. Los resultados de los isótopos estables sugieren que el agua del pre-evento (vieja) almacenada dentro de la cuenca domina el hidrograma del derretimiento de la nieve, y los resultados de los iones disueltos revelan que las trayectorias del agua subterránea ocurren predominantemente en las proximidades de la superficie durante la crecida. El carbono orgánico disuelto varía interanualmente, reflejando un esquema de derretimiento cambiante, mientras que los iones meteorizados generados a partir de las trayectorias de flujo más profundas se diluyen. El equivalente de agua de nieve total no tiene una mayor influencia en la fracción de agua derretida que alcanza a la corriente o a la tasa de escurrimiento. Los resultados de múltiples año resaltan la considerable variabilidad en cortas escalas de tiempo, limitando nuestra habilidad para detectar las influencias del cambio climático en el agua subterránea a la escala de la cabecera.摘要对于北部大型河流的研究显示,当永久冻土层融化时,深部地下水径流开始活跃,导致河川基流增大,水中风化源的离子含量增大,溶解源的有机碳含量减少。与此相反,在源头-流域的尺度上,虽然地下水/地表水的相互作用机理已经确立,但气候与水文的年际变化导致了复杂的水文和化学响应。本文展示了加拿大育空地区的一个高山不连续永久冻土地区四年的径流调查,利用稳定同位素、水中主要离子和水文观测数据加深了对产流的年际变化过程的认识。稳定同位素结果显示,储存在流域内的老水决定了融雪的水文过程线,另外,水中溶解的离子结果表明,地下水的流径主要在洪水期的近地表处出现。水中溶解的有机碳随季节变化,反映了溶解模式的变化,然而来源于深层流径的风化离子的浓度减小。总的融雪水量对到达河川的融水部分和径流系数影响不大。多年观测的结果揭示了短时间尺度下重要的年际变化,这制约着我们在源头认识气候变化对地下水的影响。ResumoA pesquisa sobre os grandes rios do norte sugere que, com o degelo do permafrost, há percursos subterrâneos profundos que se tornam ativos para as águas subterrâneas, resultando num maior escoamento de base, num aumento da concentração de iões provenientes da desagregação da rocha e numa redução das concentrações de carbono orgânico dissolvido no fluxo. Em contraste, à escala da cabeceira da bacia, onde se desenvolve a compreensão da interação águas subterrâneas/águas superficiais, a variabilidade interanual no clima e na hidrologia resulta em complexas respostas hidrológicas e químicas. Este artigo relata uma investigação sobre o escoamento superficial durante quatro anos num ambiente de permafrost alpino descontínuo em Yukon, no Canadá, usando isótopos estáveis, os iões principais dissolvidos e dados hidrométricos, para fornecer uma melhor visão da variabilidade interanual dos processos geradores do escoamento. Resultados de isótopos estáveis sugerem que o volume hídrico armazenado anteriormente ao evento do degelo dentro da bacia domina o hidrograma do degelo, e os resultados obtidos a partir dos iões dissolvidos revelam que as vias subterrâneas são predominantes muito próximos à superfície durante a inundação. O carbono orgânico dissolvido varia interanualmente, refletindo os padrões de fusão, enquanto os iões gerados a partir de desagregação mais profunda são diluídos. O volume de água proveniente da neve não tem uma grande influência na fração de água do degelo que alcança o escoamento. Os resultados de vários anos destacam a grande variabilidade em escalas de tempo curtas, limitando a nossa capacidade de detetar a influência das mudanças climáticas nas águas subterrâneas à escala da cabeceira da bacia.

A preliminary assessment of water partitioning and ecohydrological coupling in northern headwaters using stable isotopes and conceptual runoff models.

Abstract We combined a conceptual rainfall‐runoff model and input–output relationships of stable isotopes to understand ecohydrological influences on hydrological partitioning in snow‐influenced northern catchments. Six sites in Sweden (Krycklan), Canada (Wolf Creek; Baker Creek; Dorset), Scotland (Girnock) and the USA (Dry Creek) span moisture and energy gradients found at high latitudes. A meta‐analysis was carried out using the Hydrologiska Byråns Vattenbalansavdelning (HBV) model to estimate the main storage changes characterizing annual water balances. Annual snowpack storage importance was ranked as Wolf Creek > Krycklan > Dorset > Baker Creek > Dry Creek > Girnock. The subsequent rate and longevity of melt were reflected in calibrated parameters that determine partitioning of waters between more rapid and slower flowpaths and associated variations in soil and groundwater storage. Variability of stream water isotopic composition depends on the following: (i) rate and duration of spring snowmelt; (ii) significance of summer/autumn rainfall; and (iii) relative importance of near‐surface and deeper flowpaths in routing water to the stream. Flowpath partitioning also regulates influences of summer evaporation on drainage waters. Deviations of isotope data from the Global Meteoric Water Line showed subtle effects of internal catchment processes on isotopic fractionation most likely through evaporation. Such effects are highly variable among sites and with seasonal differences at some sites. After accounting for climate, evaporative fractionation is strongest at sites where lakes and near‐surface runoff processes in wet riparian soils can mobilize isotopically enriched water during summer and autumn. Given close soil–vegetation coupling, this may result in spatial variability in soil water isotope pools available for plant uptake. We argue that stable isotope studies are crucial in addressing the many open questions on hydrological functioning of northern environments.

Freezing of Subarctic Hillslopes, Wolf Creek Basin, Yukon, Canada

Abstract Freezing processes were monitored at five sites within the Wolf Creek basin, Yukon, Canada during the winter of 1998–1999. Ground temperatures were measured using thermocouples in hillslopes that had frost status ranging from permanent to seasonal. The timing of freezing and ground thermal regimes varied among the five sites and was controlled by (1) the variation in surface soil temperature, (2) frost status (seasonal vs. permanent), (3) moisture content of the active layer, (4) properties of the soil profile, and (5) the presence/absence of subsurface drainage. On slopes with permafrost, cooling was rapid and two-sided freezing closed the active layer several months after the onset of freezing. On a slope with seasonal frost only, dry soil conditions allowed frost to penetrate to depth. In contrast, a slope with seasonal frost that had continuous drainage, frost depths were shallow due to heat advected from flowing water. A simple one-dimensional conduction model with latent heat was used to simulate freezing processes. Model performance varied among the slopes, and results indicate that (1) conduction is the predominant heat transfer mechanism during freezing, (2) latent heat is the principal factor controlling frost front descent, and (3) lateral flow significantly retards frost penetration because of heat advection. This information is valuable in assessing spatial variability within tile-based models and in predicting freezing, which defines an effective end-of-season on lateral hydrological processes.

The essential value of long-term experimental data for hydrology and water management

Observations and data from long-term experimental watersheds are the foundation of hydrology as a geoscience. They allow us to benchmark process understanding, observe trends and natural cycles, and are prerequisites for testing predictive models. Long-term experimental watersheds also are places where new measurement technologies are developed. These studies offer a crucial evidence base for understanding and managing the provision of clean water supplies, predicting and mitigating the effects of floods, and protecting ecosystem services provided by rivers and wetlands. They also show how to manage land and water in an integrated, sustainable way that reduces environmental and economic costs.

Regional scale selenium loading associated with surface coal mining, Elk Valley, British Columbia, Canada

Selenium (Se) concentrations in surface water downstream of surface mining operations have been reported at levels in excess of water quality guidelines for the protection of wildlife. Previous research in surface mining environments has focused on downstream water quality impacts, yet little is known about the fundamental controls on Se loading. This study investigated the relationship between mining practices, stream flows and Se concentrations using a SPAtially Referenced Regression On Watershed attributes (SPARROW) model. This work is part of a R&D program examining the influence of surface coal mining on hydrological and water quality responses in the Elk Valley, British Columbia, Canada, aimed at informing effective management responses. Results indicate that waste rock volume, a product of mining activity, accounted for roughly 80% of the Se load from the Elk Valley, while background sources accounted for roughly 13%. Wet years were characterized by more than twice the Se load of dry years. A number of variables regarding placement of waste rock within the catchments, length of buried streams, and the construction of rock drains did not significantly influence the Se load. The age of the waste rock, the proportion of waste rock surface reclaimed, and the ratio of waste rock pile side area to top area all varied inversely with the Se load from watersheds containing waste rock. These results suggest operational practices that are likely to reduce the release of Se to surface waters.

Progress in Canadian Snow and Frozen Ground Hydrology, 2003-2007

This paper reviews advances made in Canadian snow and frozen ground hydrology between 2003 and 2006, and follows the 1999 to 2002 review of Woo and Marsh (2005). In this assessment, frozen ground hydrology encompasses the influence of both seasonally and perennially frozen ground (permafrost) on hydrology. In reviewing snow hydrology, we exclude processes associated with precipitation, glaciers and snow avalanches. With respect to frozen ground, its influence on infiltration, percolation and runoff in both permafrost and more temperate environments continues to be an active area of research. The role of permafrost at the landscape scale, and its interaction with soil properties in controlling runoff, has received particular attention. In snow hydrology, knowledge on physical processes of accumulation, redistribution and melt continue to advance through both field experiments and numerical modelling in both natural and urban settings. There also continues to be research on snow chemistry.

Hydroclimatic and hydrochemical controls on Plecoptera diversity and distribution in northern freshwater ecosystems

Freshwater ecosystems in the mid- to upper-latitudes of the northern hemisphere are particularly vulnerable to the impact of climate change as slight changes in air temperature can alter the form, timing, and magnitude of precipitation and consequent influence of snowmelt on streamflow dynamics. Here, we examine the effects of hydro-climate, flow regime, and hydrochemistry on Plecoptera (stonefly) alpha (α) diversity and distribution in northern freshwater ecosystems. We characterized the hydroclimatic regime of seven catchments spanning a climatic gradient across the northern temperate region and compared them with estimates of Plecoptera genera richness. By a space-for-time substitution, we assessed how warmer temperatures and altered flow regimes may influence Plecoptera alpha diversity and composition at the genus level. Our results show wide hydroclimatic variability among sites, including differences in temporal streamflow dynamics and temperature response. Principal component analysis showed that Plecoptera genera richness was positively correlated with catchment relief (m), mean and median annual air temperature (°C), and streamflow. These results provide a preliminary insight into how hydroclimatic change, particularly in terms of increased air temperature and altered streamflow regimes, may create future conditions more favorable to some Plecopteras in northern catchments.