Robert Daniel Moore
Relevant Degree Programs
stream temperature, forest hydrology, effects of glacier retreat and vegetation succession
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Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - May 2021)
Spatial variability in fuel moisture driven by changes in microclimate is an importantbottom-up factor determining spatial wildfire behaviour, as fuel moistureimpacts fire intensity, severity, and spread probability. However, few studies haveexamined how landscape scale patterns in near-surface microclimates impact fuelmoisture patterns. This study quantified patterns of near-surface atmospheric conditionswithin a heterogeneous forested landscape, and determined how those patternsimpact the spatial variability of fuel moisture and fire danger across the landscape.Observations across a forested landscape demonstrated that, in general,spatial variability in near-surface relative humidity and temperature was highestduring dry, clear-sky conditions. However, daytime relative humidity was an exception,being relatively homogenous across the landscape and only weakly relatedto weather conditions. Canopy cover and above-canopy radiation load predicteda significant portion of the spatial patterns in relative humidity and temperature.Changes in canopy cover had the largest impact on near-surface conditions. Opensites saw higher relative humidity, on average, due to nocturnal longwave cooling.A novel fuel moisture model was presented that predicted between 76% and 93%of the variance in observations from independent sites or time periods, which is animprovement on a more complex model currently used operationally. This modelwas combined with meteorological observations to quantify spatial patterns in fuelmoisture and potential fire danger across the landscape. Daytime fuel moisture andpotential fire danger exhibited low spatial variability, regardless of weather conditions,and only 1-hour fuel moisture was related to canopy cover or radiationload. Fuel moisture and potential fire danger were more variable at night and thatvariability increased during cool, moist periods with low wind speeds. Patterns in fuel moisture and potential fire danger were dominated by differences in nocturnallongwave cooling due to changes in canopy cover. Open sites had lower dailymean potential fire danger. When fire danger was extrapolated over a larger studyregion, daytime conditions remained homogenous. Moreover, radiation load andcanopy cover did not have a large enough direct influence on daytime fuel moistureto generate patches within the landscape that remain significantly wetter than thesurrounding landscape.
Rain-on-snow, in which rainfall occurs upon a previously existing snowpack, complicates runoff response to rain events. In some situations the snowpack absorbs rainfall; in others, runoff is enhanced by significant snowmelt. Rain-on-snow has generated major floods around the world, particularly in coastal, mountainous regions such as southwestern British Columbia, where the rugged topography can cause rapid and varying transitions between rainfall and snowfall within the same watershed, and warm, subtropical storms known as atmospheric rivers can deliver large quantities of precipitation. This thesis sought to further the understanding of rain-on-snow at the regional scale, including its role in runoff response to a wide spectrum of rain-on-snow events. Tools were developed and assessed to help achieve this goal and for use by others. First, the hydrologic utility of output from a regional weather reanalysis model was tested. Results showed air temperature and vapour pressure were likely to be useful, whereas other variables were not accurate enough to be of use. Air temperature, in particular, showed potential ability for more accurate specification of temperature gradients for hydrologic forecasting of rain-on-snow runoff. An analysis of rain-on-snow events across five automated snow pillow sites over 10 years illustrated the importance of understanding the amount of rainfall occurring at high elevations during rain-on-snow, and the relatively consistent enhancement of water available for runoff (WAR) by 25-30% due to snowmelt during large rain-on-snow events. For smaller events, a range of antecedent and meteorological factors influenced WAR generation, particularly the antecedent liquid water content of the snowpack. A probabilistic method for infilling cloud obscured pixels in optical remotely sensed snow cover imagery showed strong performance compared to more standard methods, and illustrated spatial changes in snow cover during the largest flood event within the analysis period. This method was developed to maximize information gain from satellite snowcover imagery while minimizing the transfer of disinformation. Finally, high elevation rainfall during atmospheric river events was found to be the dominant predictor of runoff response in six study catchments in the region. Antecedent snowcover provided only minimal increases in the ability to predict runoff during these events compared to rainfall alone.
Stream temperature dynamics during winter are less well studied than summer thermal regimes, but the winter season thermal regime can be critical for fish growth and development. The winter thermal regimes of Pacific Northwest headwater streams, which provide vital winter habitat for salmonids and their food sources, may be particularly sensitive to changes in climate because they can remain ice-free throughout the year and are often located in rain-on-snow zones. This study examined winter stream temperature patterns and controls in small headwater catchments within the rain-on-snow zone at the Malcolm Knapp Research Forest, near Vancouver, British Columbia, Canada.A diagnostic energy budget analysis highlighted that advective fluxes associated with hillslope throughflow inputs were a dominant control on the winter stream thermal regime. In addition, stream temperatures during rain-on-snow events were generally lower than during rain-on-ground events after controlling for air temperature. Methods for estimating throughflow temperatures embedded in stream temperature models were evaluated against field observations, and were found either not to account for the role of snow or to under- or over-predict throughflow temperatures by up to 5 °C. Therefore, a conceptual-parametric hillslope throughflow temperature model that coupled hydrologic and thermal processes, and accounted for the role of snow was developed and evaluated against field observations of throughflow temperatures. The hillslope throughflow temperature model was linked to stream energy exchange processes in order to predict stream temperature. The stream temperature model accurately predicted streamflow and winter stream temperature at three study catchments. The model also simulated lower throughflow temperatures during rain-on-snow versus rain-on-ground events, although the magnitude of cooling was less than suggested by empirical results. A key implication of this research is that climatic warming may generate higher winter stream temperatures in the rain-on-snow zone due to both increased temperature of throughflow inputs and reduced cooling effect of snow cover.
Runoff source area dynamics are controlled by the interaction of processes influencing the dynamics of water inputs at the soil surface and processes influencing vertical versus lateral flux partitioning at or below the soil surface coupled with variability in connectivity between runoff generating areas. These issues are investigated for the snowmelt-dominated Cotton Creek Experimental Watershed in southeast British Columbia, Canada. First, the controls on midwinter snowmelt are investigated. Accumulated snowmelt during the midwinter period of 2007 with nearly continuous subzero air temperatures comprised between 3% and 27% of the total snowfall. This, and other circumstantial evidence, supports the hypothesis that soil heat flux generated the midwinter snowmelt. Early-winter soil hydrothermal conditions and midwinter meteorological conditions are important controls on the midwinter melt dynamics. Second, the influences of soil hydraulic conductivity (Ks) and water input dynamics on the formation of transient perched shallow groundwater via percolation-excess processes are investigated. The results suggest that the initiation depth and maximum water table level vary according to and can be predicted by an interplay between the Ks profile and the maximum water input intensity during an event. At sites where Ks does not decrease gradually with depth, water input intensity does not appear to influence the depth of groundwater initiation. Last, seasonal variation in the spatial controls on the occurrence, timing, and persistence of shallow groundwater response are examined. The Ks of the soil at 75 cm depth is a first-order control on the distribution of sites that generate shallow groundwater response versus sites that experience only deep percolation. Upslope contributing area and slope gradient are first-order controls on the persistence of shallow groundwater response during peak flow, recession flow, and low flow periods, and runoff source areas expand and contract throughout these periods according to an interplay between catchment wetness and the spatial patterns of topographic convergence. However, controls on the space-time distribution and rates of snowmelt, and controls on vertical versus lateral flux partitioning in the soil overwhelm the importance of topographic convergence during early spring freshet periods.
The concept of hydrologic connectivity provides a temporally dynamic aspect to an otherwise static description of streamflow generation processes. The research presented in this dissertation focuses on the linkages between slopes, riparian zones and streams – the three main constitutive landscape elements of steep montane catchments – and the ways in which hydrologic connectivity affects hydrological processes. The research was conducted in Cotton Creek Experimental Watershed (CCEW), a snow-dominated meso-scale catchment located in the Kootenay Mountains, south-eastern British Columbia, Canada. First, the controls on slope water delivery to the stream were examined across a range of flow regimes. The spatial patterns and their dominant controls shifted from high to low flow. Catchment contributing area and slope length were good predictors of streamflow generation during high flow periods. At low flow, a new topographic index reflecting the spatial organization of flow pathways within a catchment was the dominant control on streamflow generation. Second, the dynamics of coupling between slopes, riparian zone and stream were examined through analysis of streamflow diel fluctuations. Periods representing high, intermediate and low baseflow were selected to investigate the dominant controls on diel fluctuations at nine stream gauges arranged in a nested design. Streamflow diel fluctuations were generated by evapotranspiration, the diurnal pattern of which was represented using vapour pressure deficit measured at a weather station within the catchment. Response times between climatic forcing and the various stream gauges revealed that both in-stream wave advection and dispersion processes, and transient storage processes in the riparian aquifers needed to be accounted for to explain spatio-temporal patterns of streamflow diel fluctuations. Last, the influence of slope water contributions to the stream on modelled solute transient storage and in-stream transport was examined. It was found that calibrated parameters representing transient storage vary systematically with the assumed magnitude and location of water fluxes to and from the stream.
Spatially distributed regional scale models of glacier melt are required to assess the potential impacts of climate change on glacier response and proglacial streamflow. The objective of this study was to address the challenges associated with regional scale modelling of glacier melt, specifically by (1) developing methods for estimating regional fields of the meteorological variables required to run melt models, and (2) testing models with a range of complexity against observed snow and ice melt at four glaciers in the southern Coast Mountains, ranging in size from a small cirque glacier to a large valley glacier. Near-surface air temperature and humidity measured over four glaciers in the southern Coast Mountains of British Columbia were compared to ambient values estimated from a regional network of off-glacier weather stations. Systematic differences between measured and ambient conditions represent the effects of katabatic flow, and were modelled as a function of flow path length calculated from glacier digital elevation models. Near-surface wind speeds were classified as either katabatic or channelled, and were modelled based on Prandtl flow (for katabatic winds) or gradient wind speeds. Models for atmospheric transmissivity, snow and ice albedo, and incoming longwave radiation were tested and developed from observations of incident and reflected shortwave radiation and incoming longwave radiation. Data from a regional climate network were used to run a degree-day model, a radiation-indexed degree-day model, a simple energy balance model (including tuned parameters for turbulent exchange) and two full energy balance models (incorporating stability corrections, with and without corrections for katabatic effects on air temperature and humidity). Modelled melt was compared to mass balance measurements of seasonal snow and ice melt. Models were also compared based on their ability to predict date of snow disappearance, given an initial snowpack water equivalence. The degree-day model outperformed the simple energy balance and radiation-indexed degree-day approaches, while the full energy balance model without katabatic boundary layer corrections yielded the lowest errors.
Master's Student Supervision (2010 - 2020)
Reductions in forest cover due to logging and natural disturbance often result in an earlier peak flow and an increase in annual yields. Most studies that consider the hydrological impacts of forest harvesting have focused on these changes to peak flows and annual yields, and not summertime low flows, even though summertime low flows are critical for instream rearing fish. This study specifically considered how forestry has impacted summertime low flows and fish habitat through time in three catchments in the southern interior of BC, two with an area of about 5 km², and one with an area of 36 km². To assess the hydrological impacts of logging, a paired-catchment analysis was applied to each day-of-year, as well as the July 1-September 30 yield. The post-harvest time series was divided into treatment periods, each about 6-10 years. To quantify the effects on of altered flows on fish habitat, an eco-hydraulic instream flow habitat assessment using a physical habitat simulation (PHABSIM)-style approach was coupled to the results of the paired-catchment analysis. In the two catchments with the longest post-harvest time series, beginning approximately two decades after the onset of harvesting, summertime low flows were consistently less than the predictions from the pre-harvest regression. Reductions in summertime low flows were less pronounced in the third catchment, where there are only 10 years of post-harvest data. The eco-hydraulic habitat modelling indicated that these reductions in streamflow often corresponded to reductions in fish habitat that typically ranged from about 20-50%. The delay between forest harvesting and reductions in streamflow is speculated to be due to regenerating forests that produces greater transpiration loss than the original, mature forests. These results begin to fill an important gap in our knowledge about longer-term impacts of logging on summertime low-flows and fish habitat in small snowmelt dominated hydrological systems of the Pacific Northwest.
Evaporation can be an important control on stream temperature,particularly in the summer when it acts to limit daily maximum streamtemperature. Evaporation from streams is usually modelled with the useof a wind function that includes empirically derived coefficients. Asmall number of studies derived wind functions for individual streams;the fitted parameters varied substantially among sites. In this study,stream evaporation and above-stream meteorological conditions (at 0.5and 1.5 m above the water surface) were measured at nine mountainstreams in southwestern British Columbia, Canada, covering a range ofstream widths, temperatures, and riparian vegetation. Evaporation wasmeasured on several days at each stream, at approximately hourlyintervals, using nine floating evaporation pans distributed across thechannels. The wind function was fit using mixed-effects models toaccount explicitly for among-stream variability in the parameters. Thefixed-effects parameters were tested using leave-one-outcross-validation. The model based on 0.5-m measurements providedimproved model performance compared to that based on 1.5-m values, withRMSE of 0.0162 and 0.0187 mm h⁻¹, respectively, relative to amean evaporation rate of 0.06 mm h⁻¹. Inclusion of atmosphericstability and canopy openness as predictors improved model performancewhen using the 1.5-m meteorological measurements, with minimalimprovement when based on 0.5-m measurements. A laboratory experimentwas conducted to test the influences of aeration and flow velocity onevaporation; no significant relationship was observed, but this may beattributable to several methodological issues.
The accuracy of gridded precipitation products in mountainous environments has been shown to be unreliable compared to other geographic areas due to the complex terrain and sparse network of stations typically found in these regions. This study is an analysis of the accuracy of the North American Regional Reanalysis (NARR) precipitation dataset for the province of British Columbia. Unlike similar gridded precipitation products, the NARR has not yet been evaluated to determine how reliably it reproduces observed patterns of precipitation in this region. The objective of this study is to assess the temporal and spatial patterns of precipitation in the NARR record in order to determine how closely it reproduces observed precipitation. A comparison of the NARR precipitation records with station precipitation records was conducted to evaluate the NARR’s ability to reproduce the interannual, monthly, and daily patterns of precipitation experienced. Streamflow records and NARR precipitation records for a number of basins throughout British Columbia were examined using a water balance approach to better understand the spatial variability of errors. A structural break in the NARR data was observed in 2003, which led to larger inaccuracies in the NARR record in subsequent years. This break was caused by a decision to exclude Canadian rain gauge data from the NARR’s data assimilation process from 2003 onwards. Several clear spatial patterns were observed in the NARR precipitation data. The NARR underpredicted precipitation in mountainous regions due to inaccuracies in its digital elevation model (DEM). The NARR overpredicted precipitation in the northern region of BC’s Interior Plateau due to a lack of available rain gauge data in this area. Finally, the NARR was found to be more accurate at modelling precipitation in areas with flat terrain and adequate station coverage, such as the southern region of the Interior and the Northeast Plateau. This analysis has shown the spatial and temporal variability of errors in the NARR dataset, allowing users to recognize both the strengths and potential shortcomings of this tool.
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 models assume that stream albedo lies between 0.03 and 0.10, based primarily on measurements from low-gradient streams with low suspended sediment concentrations. Albedo should depend upon solar elevation angle, suspended sediment, aeration, and fraction of direct vs diffuse radiation. However, there is no model available for predicting the dependence of albedo on these factors. This study quantified the dependence of albedo of mountain streams on the controlling factors in order to improve the representation of albedo in energy balance studies. Proxy measures for albedo using digital camera imagery were also developed and assessed. 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 diff use to direct solar radiation, ranging between 0.025 during cloudy periods in clear water to 0.25 for turbid water at zenith angles of less than 20 degrees. Albedo varied with discharge 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 albedo typically fluctuated between 0.08 and 0.15 on a diurnal basis at a flatwater site on the highly turbid, glacier-fed Lillooet River. Physically based representations of albedo should be incorporated into energy balance models in order to improve predictions of stream temperature, especially for future scenarios.
The objective of this study was to (1) identify the dominant processes affecting stream temperature and (2) develop and apply a process-based stream temperature model to assess the potential for managing the thermal regime of a regulated river in coastal BC through bank re-forestation and changes to release regime. The study spanned June to September 2013, when temperatures are highest and multiple salmonid species begin their spawning runs. Following June 14, a steady discharge of approximately 2.7 m³/s was released from the reservoir through a low level outlet. The reservoir developed two-layer stratification and an internal seiche that caused oscillating withdrawal of epilimnetic and hypolimnetic water that was observed to propagate at least 14 km downstream using wavelet analysis.The stream temperature model was developed with field measurements of hydrological, meteorological, and geomorphic variables that govern stream heat fluxes. A Lagrangian model was employed to model a 14 km reach of Alouette River beginning at the dam. Using a 10-min time step, an accuracy of 0.54 °C RMSE was achieved over all predictions, and 0.50 °C RMSE for daily peaks. Water parcels arriving at the downstream extent near sunset gained most heat through direct and diffuse shortwave radiation, with the greatest cooling effect associated with evaporation, tributary inflows, and bed heat conduction. Parcels arriving near sunrise gained most heat through bed heat conduction, with the greatest cooling effect associated with longwave radiation and tributary inflows.Modelling a bank re-forestation scenario resulted in study reach temperature reductions of less than 0.5 °C for mean and daily peak temperatures. A lower reservoir outlet withdrawing from the cool hypolimnion resulted in mean daily peak reductions of 4.6 °C, while raising the outlet into the epilimnion resulted in mean daily peak increases of 0.5 °C. Increased reservoir discharge caused minor increases of mean and daily peak temperatures of less than 0.15 °C. When combined, increased discharge amplified the effect of modified release depth. The results of this study stress the importance of basing warming mitigation efforts on a detailed understanding of stream heat fluxes and reservoir stratification regime in regulated systems.
Tracer dilution methods using salt and Rhodamine WT (RWT) are commonly used to measure discharge in steep mountain streams. This research addressed knowledge gaps associated with dilution methods using original ﬁeld data collected on nine streams in southwest British Columbia and discharge measurements conducted by Northwest Hydraulic Consultants. Laboratory experiments were conducted to evaluate the uncertainties associated with different procedures for calibrating the relation between salt concentration and electrical conductivity (EC) for dry salt injection, and toevaluate the effects of RWT decay due to sorption and photolysis. For salt dilution, calibration should be conducted at the in-situ stream temperature for greatest accuracy. The calibration factor varied linearly with background EC for water samples with EC less than 1000 µS/cm. For higher background EC, factors plotted below the ﬁtted relation, likely due to differences in the relative ionic abundances. Minimum mixing lengths ranged between 6.5 and 24.5 stream wetted widths, but determining the mixing length can be confounded by surface-subsurface water ﬂuxes. Probes need to be placed on opposite sides of the stream to verify adequate mixing, because probes located at different locations on the same of the stream sometimes suggested complete mixing had occurred when it in fact had not. For probes located downstream of complete mixing, breakthrough curves (BTCs) for probes located in the main current differed signiﬁcantly from probes in zones with recirculating ﬂow, even though they yielded discharge values within ± 10%. The peak of the BTC is a function of the mass of tracer injected, reach length, channel cross-sectionalarea, and the integral of a non-dimensional BTC, A*. The distribution of A* derived from analysis of 175 BTCs can be used, in conjunction with estimates of channel geometry and desired increases in EC, to estimate dosing requirements to avoid under- or over-dosing a stream reach. The calibration factor for RWT varied with turbidity, indicating that calibration is essential for each discharge measurement. Laboratory and ﬁeld experiments focused on RWT decay were confounded by other factors, so no ﬁrm conclusions could be drawn.
There has been increasing attention over the last decade to the potential effects of glacier retreat on downstream discharge and aquatic habitat. Of particular interest is the timing of "peak water," when the reduction in ice area associated with retreat begins to offset the increased rate of climatic warming-induced melt. This study examines streamflow variability downstream of Bridge Glacier, in the southern Coast Mountains of BC. The glacier currently calves into a proglacial lake, and has been retreating rapidly since 1991, when the terminus retreated into an over-deepened basin. Despite the glacier's areal decrease from 92 km² in the early 1990s to 81 km² in 2014, interannual climatic variability has obscured any resulting reductions in late-summer streamflow. The objective of this study was to diagnose trends in streamflow, as associated with the accelerating retreat of a lake-calving glacier, examining the role of calving and retreat on the magnitude and timing of summer streamflow, as well as the persistence of icebergs in the basin. Snow melt, ice melt, and rainfall-runoff were estimated using a semi-distributed hydrological model, with glacier area determined from Landsat imagery. Two seasonal discharge trends were observed, an increase in winter flow attributed to ice discharge into the lake, and a decrease in late-summer flow attributed to decreasing glacier area behind the grounding line. Decreasing streamflow trends suggested that the glacier has passed peak water, and that streamflow will continue declining with reducing glacier area.Surface and subaqueous iceberg melt were computed using an energy-balance approach, assuming that net radiation received by the ice-proximal basin was consumed by subaqueous melt and heating of 0⁰C melt water. Fractional iceberg cover in the proximal basin was determined by spectral unmixing of Landsat imagery. Estimated melt volumes suggested that in the absence of large calving events, icebergs persist for roughly a year, with high fractional iceberg cover allowing for persistence into a second year. The results from this study contribute to our understanding of streamflow response for retreating valley glaciers, many of which will likely experience a transient lake-terminating phase as the terminus retreats into over-deepened basins.
This study was motivated by an interest in understanding the physical processes drivingthe thermal regime of an ice-contact proglacial lake, in the context of its influence ondownstream water temperatures in the southern Coast Mountains of British Columbia,Canada.Field work was carried out at Bridge Glacier during the 2013 summer melt period, fromJune - September, focusing on quantifying the heat and water budgets and the thermalstructure of the lake. The proglacial lake extending from the terminus of Bridge Glacier,informally referred to as `Bridge Lake', was approximately 5.9 km² and discharged via asingle outlet. A barrier of icebergs caused the ice-proximal and distal portions of BridgeLake to behave as individual basins, although not separated by a sill.The mean net warming in summer 2013 between the glacier terminus and lake outletwas 2.7 °C. Net radiation provided the dominant energy input and net lateral advectionwas the dominant energy sink. The presence of icebergs provided a significant energy sinkand source of 0 °C melt water. Iceberg melt was equivalent to 6 - 7% of the mean dischargemeasured at the lake outlet. As icebergs are lost from Bridge Lake with continued glacierretreat, lake discharge is expected to decrease, having detrimental impacts on downstreamwater supplies for use in hydropower.The vertical thermal structure of the water column was monitored at 8 locations withinthe distal basin, with varying degrees of stratification observed with increasing distancefrom icebergs. Suspended sediment concentrations were inferred to dominate density variations, inhibiting vertical mixing of the water column induced by temperature differences.A modelling exercise provided predictions of changes to the thermal behaviour ofBridge Lake with the removal of icebergs once Bridge Glacier becomes land-terminatingand ceases to calve icebergs. With the loss of icebergs, Bridge Lake is predicted to exhibithigher water temperatures and elevated advective energy transfer associated with outflow.Drawing upon previous studies and findings from the current study, a conceptual modelfor the effect of valley glacier retreat on downstream water temperatures is proposed.
This study examined the trajectories of proglacial channel evolution in coastal British Columbia and Washington. Reach morphologies were identified by field surveys of 70 headwater reaches in ten catchments in the Coast and North Cascade Mountains. Riparian vegetation development and potential fish habitat were characterized in an additional 22 catchments using GIS analysis and satellite image interpretation. The study focused on reaches exposed by post-Little Ice Age (LIA) glacier retreat. Channel morphologies were predominantly governed by slope. The predominance of slope as a morphological control is a reflection of the landscape template imposed by the Quaternary glaciation, which appears to override most of the modern effects of the LIA. However, high sediment yield induced by post-LIA deglaciation influences channel form by providing large amounts of readily mobile sediment. Logistic regression models of riparian vegetation and forest development indicate that vegetation presence and maturity are positively correlated with reach age and negatively correlated with reach elevation. The timeline for riparian development is longer than that reported for other proglacial streams, suggesting that post-LIA instability and sediment inputs delay the establishment of riparian vegetation. A gradient-based classification tree model of potential fish presence in post-LIA channels suggests that fish may be able to access the majority of recently deglaciated headwaters, and that low-gradient, glacially carved hanging valleys may present habitat opportunities. The ability of fish to colonize proglacial streams will become increasingly important as climatic warming shifts thermal barriers for cold water species further upstream. Estimates of maximum weekly average stream temperature (MWAT) indicate that, at present, the majority of proglacial streams are thermally suitable for cold water fish. However, future projections of MWAT without basin ice cover show a 30% decline in cold water species habitat within the study basins. The work presented here contributes to the understanding of recently deglaciated headwaters by identifying first-order controls on proglacial stream morphology and riparian vegetation, which influence habitat and govern channel change in new streams.
A distinctive characteristic of proglacial streams is unsteady streamflow associated with diurnal ice melt. The role of discharge variability on downstream temperatures is not well understood. This study addressed the influence of diurnal discharge fluctuations on temperature by quantifying longitudinal heat advection and unsteady flow effects in a heat budget model for a proglacial stream in the Coast Mountains of British Columbia, Canada. Given advection has not been quantified in previous modeling studies, the dominant role of advection over surface heat fluxes found here was surprising. Advection was expected to have a considerable cooling effect due to the flow contributions from cold meltwater. This effect was confirmed while discharge generally increased; however, advection also exhibited a diurnal warming phase of similar magnitude and duration as the cooling phase, while flow generally decreased. The role of discharge variability on transverse mixing dynamics found in previous studies has been inconsistent. Here, transverse mixing lengths tended to be longer with greater tributary flow relative to the main channel. These findings need to be confirmed with further research.
Vegetation interception loss plays an important role in controlling the water balance of a watershed, especially where urban development has taken place. The aim of this study is to document the importance of urban trees as a form of ‘green infrastructure’ to reduce stormwater runoff and rainwater intensity, and cause a delay in precipitation reaching the ground. A 21 months study was carried out in the North/West Vancouver in British Columbia to determine how effective urban trees are to intercept and detain rainwater. We applied a unique methodology for measuring rain/throughfall under 54 different urban trees using a system of PVC pipes hung beneath the canopy to capture the throughfall where it drained into a rain gauge attached to a data logger. To ensure that the study adequately captured the range of throughfall variability, trees were selected to sample different landscape sites (streets, parks, and natural forested areas), elevations, tree type, health condition and species, including Douglas-fir (Pseudotsuga menziesii), Western red cedar (Thuja plicata), Bigleaf maple (Acer macrophyllum), Oak (Quercus sp.), Copper beech (Fagus sylvatica), Horse chestnut (Aesculus hippocastanum), Cherry (Prunus sp.), and Poplar (Populus sp.). Interception loss and throughfall were monitored from February 2007 until November 2008. Rainfall interception varied seasonally for all species. Interception losses accounted for on average 76.5% and 56.4% of gross precipitation for coniferous and deciduous trees, respectively. The interception loss varied depending on canopy structure, climatic conditions, and rainfall characteristics. The results showed that urban trees intercept and evapotranspire more rain than trees in forested environments. Together with the delay in runoff trees can act as an effective stormwater management tool on individual properties.
Skiing and snowboarding occur on the seasonal snow of Blackcomb Mountain, BC, which includes two glaciers: Blackcomb Glacier and Horstman Glacier. Ski operations involve the application of salt (NaCl) to the glacier and redistribution of snow on Horstman Glacier to allow for additional skiing and snowboarding during the months of June and July. Although European studies have documented that salting ski pistes can have negative effects on the environment, no research has been conducted to study the continuous application of salt onto a glacier and the effects on the downstream aquatic environment. In this study we examined the temporal changes in chloride concentration in Horstman Creek. Using neighbouring Blackcomb Glacier and Blackcomb Creek as a reference system, automatic samplers were used to collect water samples for two periods of sixteen days each during the summer of 2008. The concentration of chloride in Horstman Creek was found to be greatly elevated compared to regional background values and those of Blackcomb Creek during both sampling periods. The pattern of chloride concentration suggests that some of the NaCl applied to the glacier makes its way downstream as initial snowmelt runoff and some is stored within the glacier and released at a later time. However, despite the fact that 90 020 kg of NaCl was applied during summer 2008, the elevated concentrations did not reach a level of environmental concern during the study period.