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Stream surface albedo plays a key role in the energy balance of rivers and streams that are exposed to direct solar radiation. Most physically based analyses and models have incorporated a constant stream albedo between 0.03 and 0.10, based primarily on measurements from low-gradient streams with low suspended sediment concentrations. However, albedo should vary with solar elevation angle, suspended sediment concentration, aeration, and fraction of direct vs diffuse radiation. The objective of this study was to quantify the dependence of albedo of mountain streams on the controlling factors and to develop a predictive model for use in physically based analysis and modelling of stream temperature, especially for future climate and land use scenarios. Stream surface albedo was measured at nine sites with a variety of gradients and suspended sediment characteristics in the southern Coast Mountains of British Columbia, Canada. As expected, albedo of low-gradient, non-whitewater (flatwater) streams increased with solar zenith angle, suspended sediment concentration, and proportion of diffuse to direct solar radiation, ranging between 0.025 during cloudy periods over clear water to 0.25 for turbid water at zenith angles of less than 20 degrees. Albedo was enhanced in steep reaches or at channel steps and cascades where flow was visibly aerated, with a range of 0.09 to 0.33. In clear weather, albedo exhibited notable diurnal variability at flatwater sampling sites. For example, during late summer, surface albedotypically fluctuated between 0.08 and 0.15 on a daily basis at a flatwater site on the highly turbid, glacier-fed Lillooet River. Multiple regression models explained approximately 60% and 40% of the variance under cross validation for flatwater and whitewater data subsets, respectively, with corresponding root-mean-square errors of approximately 0.02 and 0.06.

There has been increasing attention over the last decade to the potential effects of glacier retreat on downstream discharge and aquatic habitat. This study focused on streamflow variability downstream of Bridge Glacier in the southern Coast Mountains of BC between 1979 and 2014, prior to and during a period in which the glacier experienced enhanced calving and rapid retreat across a lake-filled basin. Here we combined empirical trend detection and a conceptual-parametric hydrological model to address the following hypotheses: (1) streamflow trends in late summer and early autumn should reflect the opposing influences of climatic warming (which would tend to increase unit-area meltwater production) and the reduction in glacier area (which would tend to reduce the total volume of meltwater generated), and (2) winter streamflow should increase because of displacement of lake water as ice flows past the grounding line and calves into the lake basin. In relation to the first hypothesis, we found no significant trends in monthly discharge during summer. However, applying regression analysis to account for air temperature and precipitation variations, weak but statistically significant negative trends were detected for August and melt season discharge. The HBV-EC model was applied using time-varying glacier cover, as derived from Landsat imagery. Relative to simulations based on constant glacier extent, model results indicated that glacier recession caused a decline in mean monthly streamflow of 9% in August and 11% in September. These declines in late-summer streamflow are consistent with the results from our empirical analysis. The second hypothesis is supported by the finding of positive trends for December, January, and February discharge. Despite the modelled declines in late-summer mean monthly streamflow, recorded discharge data exhibited neither positive nor negative trends during the melt season, suggesting that Bridge Glacier may currently be at or close to the point of peak water. Further analysis of the impact of lake-terminating glaciers on downstream discharge is needed to refine the peak water model. Copyright © 2016 John Wiley & Sons, Ltd.

Meteorological observations at high elevations in mountainous regions are often lacking. One opportunity to fill this data gap is through the use of downscaled output from weather reanalysis models. In this study, we tested the accuracy of downscaled output from the North American Regional Reanalysis (NARR) against high-elevation surface observations at four ridgetop locations in the southern Coast Mountains of British Columbia, Canada. NARR model output was downscaled to the surface observation locations through three-dimensional interpolation for air temperature, vapour pressure and wind speed and two-dimensional interpolation for radiation variables. Accuracy was tested at both the 3-hourly and daily time scales. Air temperature displayed a high level of agreement, especially at the daily scale, with root mean square error (RMSE) values ranging from 0.98 to 1.21 °C across all sites. Vapour pressure downscaling accuracy was also quite high (RMSE of 0.06 to 0.11 hPa) but displayed some site specific bias. Although NARR overestimated wind speed, there were moderate to strong linear relations (r2 from 0.38 to 0.84 for daily means), suggesting that the NARR output could be used as an index and bias-corrected. NARR output reproduced the seasonal cycle for incoming short-wave radiation, with Nash–Sutcliffe model efficiencies ranging from 0.78 to 0.87, but accuracy suffered on days with cloud cover, resulting in a positive bias and RMSE ranged from 42 to 46 Wm− 2. Although fewer data were available, incoming long-wave radiation from NARR had an RMSE of 19 Wm− 2 and outperformed common methods for estimating incoming long-wave radiation. NARR air temperature showed potential to assist in hydrologic analysis and modelling during an atmospheric river storm event, which are characterized by warm and wet air masses with atypical vertical temperature gradients. The incorporation of a synthetic NARR air temperature station to better represent the higher freezing levels resulted in increased predicted peak flows, which better match the observed run-off during the event. Copyright © 2016 John Wiley & Sons, Ltd.

We collected fish samples and measured physical habitat characteristics, including summer stream temperatures, at 156 sites in 50 tributary streams in two sampling areas (Upper Fraser and Thompson Rivers) in British Columbia, Canada. Additional watershed characteristics were derived from GIS coverages of watershed, hydrological and climatic variables. Maximum weekly average temperature (MWAT), computed as an index of summer thermal regime, ranged from 10 to 23 °C. High values of MWAT were associated with large, warm, low relief watersheds with a high lake influence. Measures of community similarity suggested that the fish community changed most rapidly through a lower transition zone at an MWAT of about 12 °C and an upper transition zone at an MWAT of about 19 °C. These results were confirmed using existing fisheries inventory data combined with predictions of MWAT from a landscape-scale regression model for the Thompson River watershed. For headwater sites in the Chilcotin River watershed (which drains into the middle Fraser River), the relative dominance of bull trout versus rainbow trout (based on inventory data) decreased with increasing predicted MWAT although the distinction was not as clear as for the Thompson River sites. The fish communities in these watersheds can be characterized in terms of very cold water (bull trout and some cold water species), cold water (salmonids and sculpins) and cool water (minnows and some cold water salmonids). The two transition zones (ca 12 and 19 °C) can be used to identify thresholds where small changes in stream temperature can be expected to lead to large changes in fish communities. Such clear, quantifiable thresholds are critical components of a management strategy designed to identify and protect vulnerable fish communities in streams where poor land use practices, alone or in combination with climatic change, can lead to changes in stream temperatures. Copyright © 2015 John Wiley & Sons, Ltd.

Hydrologic classification is useful for data organization, transfer of model parameters and estimation of hydrologic sensitivity to disturbance and climatic change. Stream-flow regime has frequently been used as a basis for classification, typically by mapping regimes defined by stream-flow data from a gauging network. As an alternative, we hypothesized that ecological classification systems can predict stream-flow regime because they are based on the same characteristics that control run-off generation (soils, climate and topography). A multivariate regression tree (MRT) was used to relate stream-flow regime to the fractional coverages of the Biogeoclimatic Ecological Classification (BEC) zones within the catchment for gauged streams in British Columbia, Canada. Although the MRT identified a realistic set of regimes, only a small number of BEC zones were used as predictors, reflecting bias in the gauging network. To avoid this bias, we used a water balance model to compute mean monthly stream flow for 932 ungauged basins in British Columbia that were generated with areas between 10 and 1000 km2; these monthly stream flows were used to train an MRT model based on BEC zone coverages. This model predicted the regime at gauged basins nearly as accurately as the water balance model for pluvial, nival and glacier-supported nival regimes. Difficulties occurred in smaller basins and in specific regions where the local BEC zones were not included as predictors. Coastal hybrid nivo–pluvial regimes were poorly predicted. With further development, ecological classification systems could have great value as a tool for hydrologic classification for both research and operational applications. Copyright © 2013 John Wiley & Sons, Ltd.

Stream temperature was recorded between 2002 and 2005 at four sites in a coastal headwater catchment in British Columbia, Canada. Shallow groundwater temperatures, along with bed temperature profiles at depths of 1 to 30 cm, were recorded at 10-min intervals in two hydrologically distinct reaches beginning in 2003 or 2004, depending on the site. The lower reach had smaller discharge contributions via lateral inflow from the hillslopes and fewer areas with upwelling (UW) and/or neutral flow across the stream bed compared to the middle reach. Bed temperatures were greater than those of shallow groundwater during summer, with higher temperatures in areas of downwelling (DW) flow compared to areas of neutral and UW flow. A paired-catchment analysis revealed that partial-retention forest harvesting in autumn 2004 resulted in higher daily maximum stream and bed temperatures but smaller changes in daily minima. Changes in daily maximum stream temperature, averaged over July and August of the post-harvest year, ranged from 1.6 to 3 °C at different locations within the cut block. Post-harvest changes in bed temperature in the lower reach were smaller than the changes in stream temperature, greater at sites with DW flow, and decreased with depth at both UW and DW sites, dropping to about 1 °C at a depth of 30 cm. In the middle reach, changes in daily maximum bed temperature, averaged over July and August, were generally about 1 °C and did not vary significantly with depth. The pre-harvest regression models for shallow groundwater were not suitable for applying the paired-catchment analysis to estimate the effects of harvesting. However, shallow groundwater was warmer at the lower reach following harvesting, despite generally cooler weather compared to the pre-harvest year. Copyright © 2012 John Wiley & Sons, Ltd.

Stream surface albedo was measured at a location downstream of Place Glacier, Canada, in a steep bouldery channel. Portions of the water surface were visibly aerated as a result of the cascading flow even at lower discharges; at high flows, the stream was near-continuous whitewater. Albedo generally increased with discharge, from around 0.1 at the lower flows to 0.4 at the highest flows. This increase is consistent with the known effect of aeration on the reflectance of water. This discharge dependence of albedo needs to be accounted for in physically based models for predicting stream temperature to avoid biased predictions of net radiation. For steep proglacial streams that experience decreasing late-summer flows as a result of ongoing and future glacier recession, the associated decrease in albedo could promote higher stream temperatures, in addition to the effects of reduced flow depth and velocity. Copyright © 2011 John Wiley & Sons, Ltd.

This study was motivated by an interest in understanding the potential effects of climate change and glacier retreat on late summer water temperatures in alpine areas. Fieldwork was carried out between July and September 2007 at Place Lake, located below Place Glacier in the southern Coast Mountains of British Columbia. Place Lake has an area of 72 000m2, a single inlet and outlet channel, and an approximate residence time of 4 days. Warming between the inlet and outlet of the lake ranged up to 3 C and averaged 1.8 C, which exceeds the amount of warming that occurred over the 1 km reach of Place Creek between the lake outlet and tree line. Over a 23-day period, net radiation totalled about 210 MJ m–2, with sensible heat flux adding another 56 MJm-2. The latent heat flux consumed about 8% of the surface heat input. The dominant heat sink was the net horizontal advection associated with lake inflow and outflow. Early in the study period, temperatures between the surface and 6-m depth were dominantly at or above 4 C and were generally neutral to thermally stable, whereas temperatures decreased with depth below 6m and exhibited irregular sub-diurnal variations. The maximum outflow temperature of almost 7 C occurred in this period. We hypothesize that turbidity currents associated with cold, sediment-laden glacier discharge formed an underflow and influenced temperatures in the deeper portion of the lake but did not mix with the upper layers. Later in the study period, the lake was dominantly well mixed with some near-surface stability associated with nocturnal cooling. Further research is required to examine the combined effects of sediment concentrations and thermal processes on mixing in small proglacial lakes to make projections of the consequences of glacier retreat on alpine lake and stream temperatures.

The objective of this study was to analyse stream temperature variability during summer in relation to both surface heat exchanges and reach-scale hydrology for two hydrogeomorphically distinct reaches. The study focused on a 1·5-km wildfire-disturbed reach of Fishtrap Creek located north of Kamloops, British Columbia. Streamflow measurements and longitudinal surveys of electrical conductivity and water chemistry indicated that the upper 750 m of the study reach was dominated by flow losses. A spring discharged into the stream at 750 m below the upper reach boundary. Below the spring, the stream was neutral to losing on three measurement days, but gained flow on a fourth day that followed a rain event. Continuous stream temperature measurements typically revealed a downstream warming along the upper 750 m of the study reach on summer days, followed by a pronounced cooling associated with the spring, with little downstream change below the spring. Modelled surface energy exchanges were similar over the upper and lower sub-reaches, and thus cannot explain the differences in longitudinal temperature patterns. Application of a Lagrangian stream temperature model provided reasonably accurate predictions for the upper sub-reach. For the lower sub-reach, accurate prediction required specification of concurrent flow losses and gains as a hydrological boundary condition. These findings are consistent with differences in the hydrogeomorphology of the upper and lower sub-reaches. The modelling exercise indicated that substantial errors in predicted stream temperature can occur by representing stream-surface exchange as a reach-averaged one-directional flux computed from differences in streamflow between the upper and lower reach boundaries. Further research should focus on reliable methods for quantifying spatial variations in reach-scale hydrology. Copyright © 2010 John Wiley & Sons, Ltd.

The glaciers of western Canada and the conterminous United States have dominantly retreated since the end of the Little Ice Age (LIA) in the nineteenth century, although average rates of retreat varied from strong in the first-half of the twentieth century, with glaciers stabilizing or even advancing until 1980, and then resuming consistent recession. This retreat has been accompanied by statistically detectable declines in late-summer streamflow from glacier-fed catchments over much of the study area, although there is some geographical variation: over recent decades, glaciers in northwest BC and southwest Yukon have lost mass dominantly by thinning with relatively low rates of terminal retreat, and glacier-fed streams in that region have experienced increasing flows. In many valleys, glacier retreat has produced geomorphic hazards, including outburst floods from moraine-dammed lakes, mass failures from oversteepened valley walls and debris flows generated on moraines. In addition to these hydrologic and geomorphic changes, evidence is presented that glacier retreat will result in higher stream temperatures, possibly transient increases in suspended sediment fluxes and concentrations, and changes in water chemistry. With climate projected to continue warming over the twenty-first century, current trends in hydrology, geomorphology and water quality should continue, with a range of implications for water resources availability and management and hydroecology, particularly for cool and cold-water species such as salmonids. Copyright © 2008 John Wiley & Sons, Ltd.

The Georgia Basin–Puget Sound Lowland region of British Columbia (Canada) and Washington State (USA) presents a crucial test in environmental management due to its combination of abundant salmonid habitat, rapid population growth and urbanization, and multiple national jurisdictions. It is also hydrologically complex and heterogeneous, containing at least three streamflow regimes: pluvial (rainfall-driven winter freshet), nival (melt-driven summer freshet), and hybrid (both winter and summer freshets), reflecting differing elevation ranges within various watersheds. We performed bootstrapped composite analyses of river discharge, air temperature, and precipitation data to assess El Nino–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) impacts upon annual hydrometeorological cycles across the study area. Canadian and American data were employed from a total of 21 hydrometric and four meteorological stations. The surface meteorological anomalies showed strong regional coherence. In contrast, the seasonal impacts of coherent modes of Pacific circulation variability were found to be fundamentally different between streamflow regimes. Thus, ENSO and PDO effects can vary from one stream to the next within this region, albeit in a systematic way. Furthermore, watershed glacial cover appeared to complicate such relationships locally; and an additional annual streamflow regime was identified that exhibits climatically driven non-linear phase transitions. The spatial heterogeneity of seasonal flow responses to climatic variability may have substantial implications to catchment-specific management and planning of water resources and hydroelectric power generation, and it may also have ecological consequences due to the matching or phase-locking of lotic and riparian biological activity and life cycles to the seasonal cycle. The results add to a growing body of literature suggesting that assessments of the streamflow impacts of ocean–atmosphere circulation modes must accommodate local hydrological characteristics and dynamics. Copyright © 2007 John Wiley & Sons, Ltd. The copyright in Paul H. Whitfield's contribution belongs to the Crown in right of Canada and such copyright material is reproduced with the permission of Environment Canada.

A principal component analysis (PCA)-based synoptic typing scheme is used to assess the ability of the Canadian Centre for Climate Modelling and Analysis (CCCma) Coupled Global Climate Model (CGCM2) to reproduce daily mean-sea-level (MSL) synoptic patterns and their frequencies for the Pacific Northwest region of North America. Model output for the ‘control’ period 1961–1989 is compared against the climatology based on National Center for Environmental Prediction (NCEP) re-analysis data. Although CGCM2 is able to reproduce the full range and seasonality of 13 synoptic types it significantly under-represents three cold types and over-represents (by about 50%) three warm/wet winter types. This effect is most pronounced in winter months. Differences in frequencies between the CGCM2 runs (1961–1989 climatology and 1990–2100 IPCC SRES ‘A2’ greenhouse gases (GHG) and aerosol forcing scenario) are smaller than the differences between NCEP and CGCM2 synoptic type frequencies for the 1961–1989 control. Unresolved orographic influences and atmosphere-ocean coupling are cited as possible explanations for model deficiencies. Results suggest that application of CGCM2 output in downscaling studies examining regional impacts should take account of these potential biases. The approach adopted provides a methodology for not only assessing progress in emerging generations of more sophisticated higher resolution General Circulation Models (GCMs) (e.g. CGCM4 is under development), but also choosing the most appropriate model for regional downscaling studies. Copyright © 2006 Royal Meteorological Society.

Previous research has highlighted the relationship between snow accumulation and forest stand characteristics, as well as the effects of topography, but not the variability within stands. This study examined spatial patterns in snow accumulation within forest stands, their consistency from year to year, and the extent to which they can be predicted from commonly used stand measurements. Snow water equivalent (SWE) was measured on or near April 1, 1995 to 1997, and a forest inventory was completed at 64 points (15-m grid spacing) in each of nine stand types including mature and juvenile forests and clearcuts. Semivariograms revealed little evidence of spatial correlation among sample points, indicating that each sample could be considered statistically independent for analysis. Within the study stands, no strong spatial trends were evident through quadratic trend surface analysis. The within-stand coefficient of variation (CV) generally decreased with increasing mean accumulation. Spearman's rank correlation analysis and principal components analysis (PCA) indicated a weak to moderate similarity in snow accumulation patterns from year to year. Site-scale canopy measures do not appear to provide a reliable basis for parameterizing the variability of within-stand snow deposition. Through the fitting of general linear models (GLM), year alone accounted for 33% of the variability in snow water equivalent within stands, on average. Of the stand inventory variables measured, crown closure explained the largest proportion of the variability in SWE within each stand, but together with year never more than 43%. The strongest correlations between snow water equivalent and crown closure were found in those stands exhibiting the greatest consistency in interannual spatial patterns of snow accumulation.

The Pacific Northwest encompasses a range of hydrologic regimes that can be broadly characterized as either coastal (where rain and rain on snow are dominant) or interior (where snowmelt is dominant). Forest harvesting generally increases the fraction of precipitation that is available to become streamflow, increases rates of snowmelt, and modifies the runoff pathways by which water flows to the stream channel. Harvesting may potentially decrease the magnitude of hyporheic exchange flow through increases in fine sediment and clogging of bed materials and through changes in channel morphology, although the ecological consequences of these changes are unclear. In small headwater catchments, forest harvesting generally increases annual runoff and peak flows and reduces the severity of low flows, but exceptions have been observed for each effect. Low flows appear to be more sensitive to transpiration from vegetation in the riparian zone than in the rest of the catchment. Although it appears that harvesting increased only the more frequent, geomorphically benign peak flows in several studies, in others the treatment effect increased with return period. Recovery to pre-harvest conditions appeared to occur within about 10 to 20 years in some coastal catchments but may take many decades in mountainous, snow dominated catchments.

This study examined the thermal regime of a headwater stream within a clear-cut. The stream had a complex morphology dominated by step–pool features, many formed by sediment accumulation upstream of woody debris. Maximum daily temperatures increased up to 5 °C after logging, and were positively associated with maximum daily air temperature and negatively with discharge. Maximum daily temperatures generally increased with downstream distance through the cut block, but decreased with distance in two segments over distances of tens of metres, where the topography indicated relatively concentrated lateral inflow. Localized cool areas within a step–pool unit were associated with zones of concentrated upwelling. Bed temperatures tended to be higher and have greater ranges in areas of downwelling flow into the bed. Heat budget estimates were made using meteorological measurements over the water surface and a model of net radiation using canopy characteristics derived from fisheye photography. Heat exchange driven by hyporheic flow through the channel step was a cooling effect during daytime, with a magnitude up to approximately 25% that of net radiation during the period of maximum daytime warming. Heat budget calculations in these headwater streams are complicated by the heterogeneity of incident solar radiation and channel geometry, as well as uncertainty in estimating heat and water exchanges between the stream and the subsurface via hyporheic exchange and heat conduction. Copyright © 2005 John Wiley & Sons, Ltd.

Understanding key hydrological processes and properties is critical to sustaining the ecological, economic, social and cultural roles of Canada's varied forest types. This review examines recent progress in studying the hydrology of Canada's forest landscapes. Work in some areas, such as snow interception, accumulation and melt under forest cover, has led to modelling tools that can be readily applied for operational purposes. Our understanding in other areas, such as the link between runoff-generating processes in different forest landscapes and hydrochemical fluxes to receiving waters, is much more tentative. The 1999–2003 period saw considerable research examining hydrological and biogeochemical responses to natural and anthropogenic disturbance of forest landscapes, spurred by major funding initiatives at the provincial and federal levels. This work has provided valuable insight; however, application of the findings beyond the experimental site is often restricted by such issues as a limited consideration of the background variability of hydrological systems, incomplete appreciation of hydrological aspects at the experiment planning stage, and experimental design problems that often bedevil studies of basin response to disturbance. Overcoming these constraints will require, among other things, continued support for long-term hydroecological monitoring programmes, the embedding of process measurement and modelling studies within these programmes, and greater responsiveness to the vagaries of policy directions related to Canada's forest resources. Progress in these and related areas will contribute greatly to the development of hydrological indicators of sustainable forest management in Canada. Copyright © 2005 John Wiley & Sons, Ltd.

This study documented the spatial and temporal variability of outflow from a forested hillslope segment during snowmelt at a small mountain catchment in south coastal British Columbia, Canada. A pit 5 m wide was established just upslope from the stream channel. Outflow from the organic horizon was intercepted and measured by a single trough, and outflow from the mineral horizons was measured separately for three adjacent sections. Throughflow exhibited non-steady-state behaviour involving shifting allocations of flow amongst different sections of the outflow pit, as well as threshold effects and hysteresis in the relationship between pit outflow and water table elevation. Most of the pit outflow originated from the mineral horizons, indicating that throughflow was the dominant pathway by which water was delivered to the stream channel. Direct precipitation and snowmelt onto near-stream saturated areas can account for less than 20% of the total outflow from the hillslope segment. Throughflow from the mineral sections consistently peaked either at the same time as or earlier than stream flow from the 150-ha catchment during diurnal snowmelt cycles, indicating that throughflow appears to respond rapidly enough to contribute to snowmelt-induced peak stream flow. Pit outflow cannot be extrapolated reliably to the catchment scale on the basis of simple length- or area-based ratios. Copyright © 2004 John Wiley & Sons, Ltd.

This study examined suspended sediment concentration (SSC) during the ablation seasons of 2000 and 2001 in Place Creek, Canada, a steep, glacier-fed mountain stream. Comparison of stream flow in Place Creek with that in an adjacent, almost unglacierized catchment provided a rational basis for separating the ablation seasons into nival, nival–glacial, glacial and autumn recession subseasons. Distinct groupings of points in plots of electrical conductivity against discharge supported the validity of the subseasonal divisions in terms of varying hydrological conditions. Relationships between SSC and discharge (Q) varied between the two study seasons, and between subseasons. Hysteresis in the SSC–Q relationship was evident at both event and weekly time-scales. Some suspended sediment released from pro-glacial Place Lake (the source of Place Creek) appeared to be lost to channel storage at low flows, especially early in the ablation season, with re-entrainment at higher flows. Multiple regression models were derived for the subseasons using predictor variables including Q, Q2, the change in Q over the previous 3 h, cumulative discharge over the ablation season, total precipitation over the previous 24 h and SSC measured at 1500 hours as an index value for each day. The models produced adjusted R2 values ranging from 0·71 to 0·91, and provided tentative insights into the differences in SSC dynamics amongst subseasons. Introduction of the index value of SSC significantly improved the model fit during the nival–glacial and glacial subseasons for both years, as it adjusts the model to the current condition of sediment supply. Copyright © 2003 John Wiley & Sons, Ltd.

Knowledge of winter streamflow regimes is required in northern catchments to evaluate water supply and to assess the vulnerability of aquatic habitat. The objective of this study was to explore the nature and causes of winter streamflow variability in northern rivers through examination of a limited number of case studies involving intensive field measurements, as well as a synoptic analysis of winter streamflow measurements archived by Water Survey of Canada for rivers in Yukon Territory, Canada. Evidence was found for an abrupt decrease in discharge at freeze-up in one of the case studies and for 10 of the 25 stations in the synoptic analysis that had measurements within 30 days of freeze-up (an additional 12 stations had no measurements within 30 days of freeze-up). However, given the paucity of measurements in the early winter, the magnitude, duration and frequency of these events cannot be specified. The case studies indicate that, even where a coherent depression does not occur, discharge can fluctuate around a smooth recession trend for about the first 30 days after the onset of ice effects, probably as a result of transient storage and release of water behind ice jams. A storage-depletion model that represents streamflow as outflow from two parallel linear reservoirs provided a reasonable fit to most of the observed measurements (excluding those in the first 30 days following freeze-up), with model fit deteriorating with increasing latitude and decreasing catchment size. The effect of latitude could relate to abstraction of flow by ice production, which would cause deviations from a storage-depletion trend. Northern catchments also tended to have steeper late-winter recessions, which could reflect a lack of extensive, deep aquifers to maintain late-winter discharge. The tendency to poorer model fit in smaller catchments could reflect a problem with data reliability, since it is more difficult to find good winter gauging sections in smaller streams. Some evidence for temperature-related discharge fluctuations was found in both the case studies and synoptic analyses. However, the magnitude of these effects appears to be about ±10 to 15%, at most, and not to be consistent between winters. Further advances in understanding winter streamflow variability will require frequent measurements on a range of streams over a number of winters. Copyright © 2002 John Wiley & Sons, Ltd.

Many efforts to model stream temperature by using an energy budget approach have not accounted for view factors in modelling stream surface radiative exchanges, used informal approaches for computing them, or relied on calibration, which is not applicable for prediction at unmonitored sites or for predicting the effects of changes in riparian vegetation. In this paper, equations are derived for calculating view factors on the basis of geometric considerations for streams with and without riparian forest. The solutions can accommodate vegetation overhanging the stream surface. Example calculations illustrate the substantial variability of view factors across the stream width, which has implications for the estimation of view factors from point-scale radiation measurements over the stream surface, and the important influence of overhanging vegetation on view factors for narrow streams. View factors computed from the geometric model agreed well with view factors computed from hemispherical photography for streams ranging from 1 to almost 50 m wide, indicating that the model appears to be reasonably robust to deviations from the simplified geometry assumed by the model. In addition to their use in modelling stream surface energy exchanges, the solutions could also be adapted for application to energy balance and microclimate modelling in linear forest openings, such as seismic lines used in oil and gas exploration. Copyright © 2013 John Wiley & Sons, Ltd.

The relations between water-table depth in a shallow forest soil and topographic characteristics derived from a raster digital elevation model (DEM) were studied. Water-table depths at times of observation, and peak levels between times of observation, were measured weekly during an autumn-winter rainy season at 59 wells in a catchment (ca 0.04 km 2 ) drained by an ephemeral stream, located 80 km east of Vancouver, Canada. Digital elevation models with grid spacings of 4, 8 and 16 m were derived from a ground survey and values of a (upslope contributing area per unit contour length), tanβ (surface slope) and x (a measure of surface curvature) were computed from the DEMs. To avoid problems with data censoring when the water-table dropped below the bottom of some wells, the depths were discretized into classes and discriminant analysis was used to relate water-table depth classes to the topographic indices. The relations were derived using data from 30 wells and were tested on data from the other 29 wells to provide an independent test of predictive capability. The index In(a/tanβ) provided more reliable classifications than a multiple discriminant analysis using In(a), tanβ and x as separate predictor variables. Water-table depths at some wells were consistently misclassified (e.g. 0-3% correct classifications), whereas at others they were classified correctly in up to 100% of cases. Consistent misclassification at individual wells could reflect either the effects of errors in the derived topographic indices (through errors in the DEM or the algorithms used to calculate the indices) or phenomena not related to surface topography, such as variability in soil properties or differences between the surface topography and the topography of the base of the soil profile. The predictive accuracy and statistical significance of derived relations decreased as the DEM grid size increased from 4 to 8 to 16 m. These results are valid only for predictions of water-table depths at points. Further research should explore the effect of grid scale on relations between grid-averaged water-table depths and topographic indices and on methods to parameterize subgrid-scale variability.

Stream temperature and riparian microclimate were characterized for a I-5 km wildfire-disturbed reach of Fishtrap Creek, located north of Kamloops, British Columbia. A deterministic net radiation model was developed using hemispherical canopy images coupled with on-site microclimate measurements. Modelled net radiation agreed reasonably with measured net radiation. Air temperature and humidity measured at two locations above the stream, separated by 900 m, were generally similar, whereas wind speed was poorly correlated between the two sites. Modelled net radiation varied considerably along the reach, and measurements at a single location did not provide a reliable estimate of the modelled reach average. During summer, net radiation dominated the surface heat exchanges, particularly because the sensible and latent heat fluxes were normally of opposite sign and thus tended to cancel each other. All surface heat fluxes shifted to negative values in autumn and were of similar magnitude through winter. In March, net radiation became positive, but heat gains were cancelled by sensible and latent heat fluxes, which remained negative. A modelling exercise using three canopy cover scenarios (current, simulated pre- wildfire and simulated complete vegetation removal) showed that net radiation under the standing dead trees was double that modelled for the pre-fire canopy cover. However, post-disturbance standing dead trees reduce daytime net radiation reaching the stream surface by one-third compared with complete vegetation removal. The results of this study have highlighted the need to account for reach-scale spatial variability of energy exchange processes, especially net radiation, when modelling stream energy budgets. Copyright © 2010 John Wiley & Sons, Ltd.

1. Applied to intact Na-rich muscle cells, sanguinarine causes an increased 22Na efflux in the presence or absence of extracellular K+ or of ouabain. 2. The increased 22Na efflux does not represent Na:Na exchange as indicated by the fact that it is not associated with an increase in one-way isotopic Na influx nor is it abolished by the absence of external Na+. 3. In both K-free Ringer and K-free Ringer containing ouabain, sanguinarine not only increases one-way efflux of 22Na, it also induces net efflux of Na+ in the face of both an electrical and a concentration gradient. Moreover, the induction of net Na+ efflux occurs in the face of an approximately fourfold increase in PNa. These surprising results lead to the conclusion that, contrary to all experiments, sanguinarine induces active Na+ efflux even in K-free Ringer containing 10(-3) M-ouabain. 4. Sanguinarine depolarizes the Na-loaded muscle to approximately the same value, -54 mV, regardless of the presence or absence of extracellular K+. This depolarization is most likely secondary to the increase in PNa. 5. Sanguinarine causes a net loss of K+, presumably secondary to the depolarization. 6. The stimulation of net Na+ efflux is not correlated with the depolarization. The stimulation in K-free conditions (with or without ouabain), which is associated with the largest depolarization, produces an increment in net Na+ efflux which is not significantly different from the increment in net Na+ efflux in 10 mM-K+ Ringer where the depolarization is smallest. 7. Although sanguinarine increases active Na+ efflux in intact cells, it inhibits the isolated (Na+ + K+)-ATPase, presumably due to interaction with a site on the inner face of the membrane fragment. 8. The surprising stimulation of active Na+ efflux in the presence of 10(-3) M-ouabain must be due to interaction of sanguinarine with a site on the outer face of the membrane, perhaps the K+ activation site. It seems probable that the component of active Na+ efflux induced by sanguinarine is mediated by the Na pump. Sanguinarine may produce a K+-like effect upon the Na pump with consequent unbinding of ouabain.

The hypothesis that part of the insulin transduction system consists of a co-ordinated stimulation of the Na pump and of Na-H exchange by the hormone (Moore, 1981) requires that insulin plays a physiological role in the regulation of intracellular Na+. Moreover, this model predicts that in hypoinsulinaemic states, such as diabetes and fasting, intracellular pH and intracellular ATP levels would be depressed. The present study tests the hypothesis that in hypoinsulinaemic states intracellular Na+ is increased and intracellular ATP is decreased by measuring these parameters in soleus muscles removed from both diabetic and fasted rats. When rats were made diabetic by injection of streptozotocin (SZ) plasma insulin significantly decreased by 24 hr and plasma glucose and triglyceride levels increased. Intracellular Na+ was significantly elevated by 48 hr after injection of SZ. The elevation ranged from 18 to 48% and persisted for the duration of the experimental observation (up to 28 days). Intracellular ATP decreased significantly by the seventh day after SZ injection and remained depressed by about 24% for the duration (35 days) of the observation. In one series, a significant negative correlation was seen between plasma insulin levels and intracellular Na+ of both SZ-diabetic animals and their controls. Intracellular Na+ also significantly increased when hypoinsulinaemia was induced by fasting. Again, intracellular ATP did not decrease until after the elevation of intracellular Na+. After 72 hr of fasting, intracellular ATP was still decreased in spite of normal plasma glucose levels. Insulin therapy of SZ diabetic rats restored intracellular ATP and plasma glucose to normal, but did not restore intracellular Na+ to normal levels. The results confirm two predictions of the 'insulin transduction system model (Moore, 1981). Most strongly supported is that part of the model which indicates that the Na pump is regulated by physiological levels of insulin. This is especially convincing since hypoinsulinaemia produced by a non-pharmacological procedure, fasting, was associated with an increase in intracellular Na+.