Quesnel Lake Research Articles

Annual pulses of copper-enriched sediment in a North American river downstream of a large lake following the catastrophic failure of a mine tailings storage facility

Failures of mine tailings storage facilities (TSF) can have profound and long-lasting effects on the downstream receiving environment. Virtually all spills to date have been into river systems without large lakes that may buffer downstream impacts. In August 2014, the failure of the Mount Polley copper (Cu)-gold mine TSF in British Columbia, Canada, released ~25 × 106 m3 of water and solids; globally, this is the second largest TSF spill in history. Over 18 × 106 m3 was delivered to Quesnel Lake, which is ~9 km from the TSF and is the third deepest lake in North America, and a crucial habitat for Pacific salmon and trout populations. We determined the sediment-associated Cu concentrations and fluxes in Quesnel River, downstream of the lake, from August 2014 to February 2021 based on the analysis of >400 samples of sediment, mainly collected using a continuous-flow centrifuge. During each winter since the spill, Cu concentrations in the fluvial sediment in the upper reaches of the river (~35 km from the TSF) were elevated relative to regional background concentrations and samples collected before the spill. Maximum Cu concentrations were ~410 mg kg−1 which exceeds Canadian sediment quality guidelines for the protection of aquatic organisms (197 mg kg−1). Monitoring of Quesnel Lake since the spill shows that these annual pulses in the winter are due to resuspension of unconsolidated tailings and sediments at the bottom of Quesnel Lake, during autumnal lake turnover, which become mixed throughout the water column and subsequently flow into Quesnel River. Results show that while large lakes may buffer downstream aquatic systems from contaminated sediment, they may prolong the environmental impact. These findings are crucial in understanding how lake processes may modify the effects of TSF spills on downstream aquatic systems.

The Fate of a Lake After a Dramatic Mining Disaster

Researchers tracked long-term sediment dynamics in Canada’s Quesnel Lake following the 2014 failure of a dam that spilled record-breaking amounts of contaminated mining waste.

Invertebrate metal accumulation and toxicity from sediments affected by the Mount Polley mine disaster.

On August 4, 2014, a tailings dam failed at the Mount Polley copper and gold mine near Likely, British Columbia, Canada, releasing approximately 25 M m[Formula: see text] of contaminated water and solid tailings material into Polley and Quesnel lakes. Water, sediment, freshwater scuds (Hyalella azteca), and mayfly larvae (Ephemeroptera) were collected during the summer of 2018 from Polley Lake, affected and unaffected sites in Quesnel Lake, and both mine-contaminated and clean far-field sites as references. Analytical results indicated that invertebrates from sites affected by the tailings breach had elevated metal concentrations relative to those from non-affected or reference sites. We conducted a controlled laboratory exposure to determine if laboratory-reared Hyalella azteca metal concentrations were related to field-collected water or sediments from the same sites as the field study. Half of the replicates prevented amphipods from directly contacting sediments (water-only exposure), while the other half allowed them direct access (sediment and water exposure). Whole-body Cu concentration was highest in Hyalella exposed to substrate from the most contaminated sites as well as in treatments where they were allowed direct access to sediments. Hyalella having direct access to metal-contaminated sediments showed reduced survival and growth relative to those in reference or control treatments. These results suggest that metals from the fine sediments associated with the Mount Polley mine disaster are bioavailable and potentially toxic to epibenthic invertebrates, even several years after the initial breach.

Initial Distribution and Interannual Decrease of Suspended Sediment in a Two‐Basin Lake Following a Massive Mine Tailings Spill: Quesnel Lake, BC, Canada

AbstractOn 4 August 2014, a tailings dam failure at Mount Polley Mine in central British Columbia led to the largest short‐term release of mine waste into a lake ever recorded. Once released by the breach, slurry entered the smaller of Quesnel Lake’s two basins, called the West Basin, from which the lake drains northwest into the Quesnel River. An estimated 38,000 ± 11,000 tonnes of fine solids remained suspended in the West Basin on 10 September 2014, 37 days postspill. This decreased to within background levels (<300 tonnes) by June 2015, by which time ∼4,000 tonnes of sediment had flowed from the West Basin into the Quesnel River, and ∼31,000 tonnes had been transported east into the main basin, the direction opposed to the mean hydraulic gradient. Here, we evaluate sediment transport in Quesnel Lake following the Mount Polley tailings dam spill. We apply conservation of mass in two ways: using data collected between 12 August 2014 and 15 October 2020 to estimate suspended sediment mass and mass flows into and out of the West Basin; and using one‐ and two‐basin completely mixed models. Suspended sediment concentrations were highly elevated through the first three seasons postspill, then fluctuated within a gradually decreasing, seasonal cycle. The observed mass trend and an analytical mass balance model of a simplified, two‐basin system suggest that suspended sediment mass will fall to below the median prespill mass by 7 ± 5 years postspill.

Erosion, deposition and contamination by high‐magnitude subaqueous debris flows and turbidity currents: Insights from the failure of a tailings dam near Quesnel Lake, British Columbia

AbstractThe 4 August 2014 failure of Mount Polley mine tailings dam in central British Columbia, Canada, is the worst environmental disaster in British Columbia history. Around 25 million m3 of water, tailings solids and dam construction materials travelled as a slurry flow down nearby Hazeltine Creek. About 18.6 million m3 of tailings and displaced coarse sediment entered into the narrow, deep, fjord‐like Quesnel Lake. Multibeam echosounding, sub‐bottom profiling, sediment cores and theoretical models are used to examine erosion and deposition on the Hazeltine Creek fan‐delta and the bed of Quesnel Lake by subaqueous sediment density flows generated from the slurry. Strong to very strong subaqueous debris flows eroded two deep subaqueous channels on the fan‐delta in a period of less than 12 h. A model for subaerial debris‐flow erosion overestimates submerged delta‐front erosion rates in the channels because of evolution of the subaqueous debris flows and incomplete liquefaction of the eroding bed. The debris flows deposited a localized debrite with a hummocky surface composed of fine tailings and coarse displaced fan‐delta and fluvial sediment. A flat, featureless, surface composed of fine‐grained sediment adjacent to the debrite is interpreted as debrite/turbidite resulting from debris flows proximally and turbidity currents distally. Copper concentrations in cores are highly elevated compared to background concentrations in pre‐event native lacustrine sediment. Deposits from subaqueous sediment flows generated by earthquakes and glacial lake outburst floods are generally thinner than those in Quesnel Lake caused by the tailings dam failure.

Seasonal Turbidity Linked to Physical Dynamics in a Deep Lake Following the Catastrophic 2014 Mount Polley Mine Tailings Spill

AbstractThe catastrophic August 2014 Mount Polley tailings spill, the second largest ever documented, sent ~18 Mm3 of waste plunging to the bottom of the >100 m deep West Basin of Quesnel Lake, British Columbia, a critical West Coast salmon habitat. To understand the impact of the spill on the lake, including the fate of suspended solids, we examine changes in physical water properties over 11 years (2006–2017) using water column profiles, moored timeseries, and satellite imagery. Contaminated waters were initially largely confined to the hypolimnion; however, during autumn 2014 turnover, turbid waters were mixed to the surface, resulting in the clear blue lake turning bright green. Twelve months after the spill, the lake's temperature, conductivity, and turbidity temporarily returned to pre‐spill conditions; however, initiation of mine effluent discharge in late 2015 was associated with a subsequent 15 μS cm−1 conductivity increase above historic values. Importantly, a post‐spill 1–2.5 formazin turbidity unit hypolimnetic turbidity increase was observed during spring and fall turnovers of 2015–2017, which appeared to be due to resuspension of a thin layer of unconsolidated spill‐related material from the lake bed driven by large internal seiche motions. This process implies spill contaminants may be seasonally mobilized into the water column, with potentially detrimental impacts on aquatic ecology. Our findings underscore that basin‐scale physical processes, including seasonal turnover and internal seiches, must be accounted for, even in deep lakes, to understand the long‐term impact of the ever increasing number of tailings spills into aquatic ecosystems.

In the Wake of the Mount Polley Mine Tailings Breach: Tailings Dam Design, Innovation, and Practice Changes

The Mount Polley tailings dam in British Columbia (BC), Canada, failed in 2014, spilling approximately 21 million m3 of water and tailings (estimated as approximately 50/50 water and tailings) into Hazeltine Creek, Polley Lake, and Quesnel Lake. In January 2015, the Ministry of Energy and Mines (MEM) issued a report by the Independent Review Panel (Panel) that assessed the failure. At the same time, it also launched a separate investigation, led by the chief inspector of mines, into the root cause of the problem, the failure mechanism, and the operational and governance aspects that contributed to the failure. This report was issued in November 2015.

A synoptic climatology of potential seiche‐inducing winds in a large intermontane lake: Quesnel Lake, British Columbia, Canada

AbstractExcitation of basin‐scale, internal waves (i.e., internal seiches) in lakes require spatially homogeneous wind fields that vary on time scales comparable to the seiche period, which can be on the order of several days in large lakes. We evaluate 2 years (October 1, 2016 to September 30, 2018) of 15‐min wind data from a shore‐based meteorological station to identify strong wind episodes likely to excite internal seiches in a large and geometrically complex lake surrounded by convoluted topography, Quesnel Lake, British Columbia, Canada. Our findings include the identification of strong wind event seasonality, with peak mean monthly wind speeds in April and November, and minimum mean monthly wind speeds in August. Using geopotential heights (GPHs) from 1.5° × 1.5° gridded reanalysis data to reconstruct the atmospheric state for each strong wind episode, two primary synoptic patterns are identified that, in conjunction with local topographic channelling, lead to either easterlies or westerlies occurring at our sampling station, with strong easterly episodes three times more frequent than westerly episodes. This highlights the important role that developing low‐pressure systems in the Northeastern Pacific Basin have in setting up the GPH gradient required for persistent strong winds at Quesnel Lake, in the hours and days before these storms make landfall. The projection of synoptic patterns of strong wind events onto a 4 × 3 self‐organizing map clustered strong wind events by mean wind direction, similar to the results of a manual classification. Methods to identify the strong wind episodes and the resulting self‐organizing map are both evaluated in‐part by two case studies where strong winds are known to have excited a basin‐scale baroclinic response in Quesnel Lake.

The bacterial community of Quesnel Lake sediments impacted by a catastrophic mine tailings spill differ in composition from those at undisturbed locations \u2013 two years post-spill

The West Basin of Quesnel Lake (British Columbia, Canada) suffered a catastrophic disturbance event in August 2014 when mine tailings and scoured natural material were deposited into the lake’s West Basin due to an impoundment failure at the adjacent Mount Polley copper-gold mine. The deposit covered a significant portion of the West Basin floor with a thick layer of material. Since lake sediments host bacterial communities that play key roles in the geochemical cycling in lacustrine environments, it is important to understand which groups inhabit the newly deposited material and what this implies for the ecological function of the West Basin. Here we report a study conducted two years post-spill, comparing the bacterial communities from sediments of both disturbed and undisturbed sites. Our results show that sediments from disturbed sites differed in physical and chemical properties than those in undisturbed sites (e.g. higher pH, particle size and Cu concentration). Furthermore, bacterial communities from the disturbed sites appeared to be legacy communities from the tailings impoundment, with metabolic potential revolving mainly around the cycling of S and metals, whereas the ones from the undisturbed sites were associated with the cycling of N.

Risks and Impacts to First Nation Health and the Mount Polley Mine Tailings Dam Failure

In August 2014, the Mount Polley Mine tailings dam was breached, releasing millions of cubic metres of tailings water and tailings into Polley Lake, Quesnel Lake, and Hazeltine Creek in British Columbia (BC), Canada. To date, no assessment has identified the communities impacted by this event, nor how they were impacted, from a social or health perspective. This qualitative study uses a community-based participatory research approach to identify (1) First Nations impacted by this incident and (2) impacts to Aboriginal health experienced by these communities. To address these gaps in knowledge, the First Nations Health Authority funded the project team to complete the first two phases of a health impact assessment. This work draws attention to the strong links between First Nations, the land and resources, culture, and associated health outcomes. In considering the importance of Aboriginal health and culturally appropriate health pathways, the project team identified 4 key impacts: environmental dispossession, emotional stress, altered dietary patterns, and changes in physical activity. The similarity in impacts associated with the Mount Polley tailings dam failure for many First Nations in BC is best understood through an in-depth understanding of the importance of the Fraser River as a source of salmon for their communities. This work documents the unidentified and unfulfilled need to ameliorate the extent of emotional trauma prompted by real or perceived threat to salmon health, a threat exacerbated by a lack of reliable information from trusted sources in the aftermath of the breach. Relevant recommendations are also provided.

"Our Economy Walks on the Land": Secwepemc Resistance and Resilience After the Imperial Metals Mt. Polley Tailings Storage Facility Breach

Discusses Indigenous responses to Canada’s, and one of the world’s, largest and most impactful mining disasters of its kind, [on] August 4, 2014, [when] approximately 25 million cubic metres of contaminated water and ground mining waste, or tailings, spilled into Edney Creek, Polley Lake, Hazeltine Creek, and Quesnel Lake.

Carbonate-Hosted Nonsulfide Pb-Zn Deposits of the Quesnel Lake District, British Columbia, Canada

Carbonate-hosted Pb and Zn mineralization in the Quesnel Lake district (Flipper Creek, Dolomite Flats, Main, Gunn, and Que deposits) forms an ~8-km-long belt in metasedimentary and metavolcanic rocks of the Cariboo terrane, a displaced piece of the ancestral North American margin. The mineralization is strata-bound, dolostone hosted, and consists of Pb- and Zn-bearing sulfide and nonsulfide minerals. The supergene nonsulfides mimic the morphology of preexisting sulfides occurring as disseminations, veins, and fracture fillings, and irregular replacement zones in the Neoproterozoic to Upper Cambrian dolostones of the Cunningham Formation. The main sulfides are galena, sphalerite, and minor amounts of pyrite, which have been partially or completely transformed into nonsulfide minerals by supergene processes. The main nonsulfide minerals are smithsonite [ZnCO 3 ] and hemimorphite [Zn 4 Si 2 O 7 (OH) 2 ⋅(H 2 O)], with variable amounts of cerussite [PbCO 3 ], anglesite [PbSO 4 ], hydrozincite [Zn 5 (CO 3 ) 2 (OH) 6 ], and iron oxides. The δ 18 O VSMOW , δ 13 C VPDB , and 87 Sr/ 86 Sr values of the nonmineralized and mineralized dolostones are indistinguishable and consistent with the composition of carbonates that underwent postdepositional recrystallization and isotopic reequilibration during deep burial fluid-rock interaction. The δ 18 O VSMOW and δ 13 C VPDB values range from 17.4 to 20‰ and −0.8 to +1.4‰, respectively, and 87 Sr/ 86 Sr values are above 0.71048. Carbon and oxygen ratios of smithsonite show a limited range of values, which are slightly lower than those of the host dolostones with δ 18 O VSMOW values of 16.9 to 17.8‰ and δ 13 C VPDB values of −1.6 to −0.9‰. The carbon isotope values suggest that the host dolostones are the carbon source for smithsonite. The δ 18 O smithsonite values are lower than typical values for nonsulfides formed under warm, humid, and arid-to-hyperarid climates elsewhere in the world. The precipitation temperatures derived from the isotope data for the Quesnel Lake smithsonite vary between 9° and 33°C. This temperature range is favorable for supergene smithsonite formation. For most deposits of the Quesnel Lake district examined in this study, close spatial relationships (including textures and morphological similarities) between sulfide and nonsulfide zones, coexisting sulfide-nonsulfide assemblages, and stable oxygen and carbon isotope data suggest that the oxidation of sulfides occurred after the Laramide orogeny (

Lithospheric mantle xenoliths sampled by melts from upwelling asthenosphere: The Quaternary Tasse alkaline basalts of southeastern British Columbia, Canada

The Quaternary Tasse basalts are exposed near the north shore of Quesnel Lake in southeastern British Columbia. They host a variety of mantle xenoliths consisting predominantly of spinel lherzolite with minor dunite and pyroxenite. Mineralogically, the xenoliths are composed of olivine, orthopyroxene, clinopyroxene and spinel characterized by forsterite (Fo87–93), enstatite (En90–92), diopside (En45–50–Wo40–45–Fs5), and Cr-spinel (6−11wt.% Cr), respectively. All of the mantle xenoliths are coarse-grained and show granoblastic textures. Clinopyroxene and spinel display textural evidence for chemical reactions with percolating melts.The mantle xenoliths are characterized by restricted Mg-numbers (89−92) and low abundances of incompatible elements (Ba=2−11ppm; Sr=3−31ppm) and Yttrium (1−3ppm). On the basis of REE patterns, the xenoliths are divided into three groups reflecting the various degrees of mantle metasomatism: (1) Group 1 consists of concave-up LREE patterns (La/Smcn=0.48−1.16; Gd/Ybcn=0.71−0.92); (2) Group 2 possesses flat to moderately LREE-enriched patterns (La/Smcn=1.14−1.92; Gd/Ybcn=0.87−1.09); and (3) Group 3 is characterized by strongly LREE-enriched patterns (La/Smcn=1.53−2.45; Gd/Ybcn=1.00−1.32). On MORB-normalized trace element diagrams, the majority of the xenolith samples share the enrichment of LILE (Rb, Ba, K), U, Th, Pb, Sr and the depletion of HFSE (Nb, Ta, Ti, Y) relative to REE. These geochemical characteristics are consistent with a compositionally heterogeneous subcontinental lithospheric mantle source that originated as subarc mantle wedge peridotite at a convergent plate margin.The Tasse basalts have alkaline compositions characterized by low SiO2 (44−46wt.%) and high alkali (Na2O+K2O=5.1−6.6wt.%) contents. They are strongly enriched in incompatible elements (TiO2=2.4−3.1wt.%; Ba=580−797ppm; Sr=872−993ppm) and, display OIB-like trace element patterns (La/Smn=3.15−3.85; Gd/Ybn=3.42−4.61). They have positive εNd (+3.8 to +5.5) values, with 338−426Ma depleted mantle model ages, and display uniform OIB-like Sr (87Sr/86Sr=0.703346−0.703591) and Pb (206Pb/204Pb=19.40−19.58; 207Pb/204Pb=15.57−15.60; 208Pb/204Pb=38.99−39.14) isotopic compositions. The basalts erupted discontinuously along a >1000km long SE-NW-trending linear belt with minimal compositional variation indicative of a homogenous mantle source. The Sr−Nd−Pb isotope and trace element systematics of the alkaline basalts suggests that they originated from partial melting of an upwelling asthenospheric mantle source. Melting of the asthenospheric mantle might have stemmed from extension of the overlying lithosphere in response to the early stages of back-arc basin opening in the Omineca and Intermontane belts. Ridge subduction beneath the Canadian Cordillera might have played an important role in the weakening of the lithospheric mantle prior to its extension. Alternatively, melting of the upwelling asthenosphere in response to the delamination of the lithospheric mantle beneath the Rocky Mountain Trench might have generated the alkaline lavas.

Relocating A Historical Black Swift Nest and the Importance of Nest Sites to the Species

In British Columbia, the Black Swift (Cypseloides niger) is thought to breed throughout the southern half of the province (Campbell and others 1990); however, relatively few Black Swift nests have been located and described. Grant (1966) located the 1st active Black Swift nest in the province 29 km north of Vernon at Harlan Creek. Tyson (2004) located the 2nd active nest at Cascade Falls 16 km northeast of Mission. In 2004, I located an active nest at Brandywine Falls 14 km south of Whistler. There are additional accounts that suggest nesting, but active nests have not been located or described. The 1st breeding evidence of Black Swifts was a developing egg in a bird collected on 16 June 1901 near Chilliwack (Brooks 1917). Jobin (1955) reported breeding colonies of Black Swift on cliffs near the north arm of Quesnel Lake, and 10 km northwest of Kleena Kleene. During wildlife inventories in Kootenay National Park, Black Swifts were observed flying near Helmut Falls, Sinclair Canyon, and Marble Canyon; nesting was suspected at the latter site (Poll and others 1984). In June 2001, during a cave inventory west of Prince George, a dead juvenile Black Swift was found at the entrance of Redemption Cave; Black Swifts were observed entering the cave in July, but active nests were not located (Northern BC Caving Club 2015). Black Swifts have been observed flying from sea caves near Hotsprings Cove (Campbell and others 1990) and near Port Renfrew (Tyson 2004). Given the limited number of known Black Swift nest sites in British Columbia, each of the known nest sites are increasingly valuable to the conservation of the species and determining the status of unconfirmed sites should be a priority. Beebe (1959) provided the 1st evidence of Black Swift nesting in British Columbia. On 16 August 1958, a flightless Black Swift nestling was delivered to Beebe’s home in Victoria. Apparently, the nestling was 1 of 2 Black Swift nestlings that were collected by a teenage boy on 15 August from a single nest located 4.57 m on a vertical rock face adjacent to a waterfall, approximately 2 mi north of Clinton, British Columbia. Beebe cared for the nestling by feeding the bird goat’s milk, termites, and crickets; the nestling survived and was successfully released in Victoria, British Columbia on 25 August. There is no indication that Beebe attempted to relocate the nest site, nor that it has ever been relocated (Campbell and others 1990). There are a number of reasons that would deter readers of Beebe’s account from attempting to relocate the Clinton nest site: (1) the site location is a second-hand account from an unnamed teenage boy; (2) the waterfall is unnamed; and (3) the area surrounding Clinton is generally not known for waterfalls. The mention of 2 nestlings being removed from a single nest raises doubt of Beebe’s account. It is now well established that Black Swifts lay a single egg per nest (Lowther and Collins 2002; Hirshman and others 2007); therefore, if 2 nestlings were collected in 1958, this would suggest 2 active nests were involved. In 2014, 56 years after Beebe’s nest account, I relocated what is presumed to be the original nesting site described by Beebe (1959). On 29 July 2014, I visited a series of waterfalls located approximately 6.4 km north of Clinton (Fig. 1), and conducted a 2-h search for evidence of nesting Black Swifts. I found 1 active Black Swift nest, but it was immediately clear that a more thorough inventory of the site was needed. I revisited the site on 3 August, and conducted a 7-h inventory over the approximately 500-m length of the Clinton Creek waterfall complex. No additional active Black Swift nests were located; however, I observed 4 empty nest structures that appeared to be Black Swift nests from previous years. The active Black Swift nest was beside the southern edge GENERAL NOTES

The impact of a catastrophic mine tailings impoundment spill into one of North America's largest fjord lakes: Quesnel Lake, British Columbia, Canada

AbstractOn 4 August 2014, a catastrophic breach of the Mount Polley mine tailings impoundment released ~25 M m3 of tailings and water and scoured an unknown quantity of overburden into the West Basin of Quesnel Lake. We document Quesnel Lake and Quesnel River observations for 2 months postspill. Breach inflows raised Quesnel Lake by 7.7 cm, equivalent to ~21 M m3. The West Basin hypolimnion was modified immediately, exhibiting increased temperature (~5°C to 6–7.5°C), conductivity (110 to 160 μS/cm), and turbidity (<1 to 200–1000 nephelometric turbidity units (NTU)). Cooscillating seiches moved West Basin hypolimnetic water both westward and eastward contaminating the Main Basin. Postspill, high‐turbidity water propagated eastward (~1 cm/s), introducing a persistent ~20 m thick layer below the thermocline and an ~30 m thick layer at the bottom. The contaminant introduction, mobilization, and bioaccumulation may pose risks to resident and anadromous fish stocks, which support recreational, commercial, and First Nations fisheries.

Stock‐Specific Migration Pathways of Juvenile Sockeye Salmon in British Columbia Waters and in the Gulf of Alaska

AbstractWe outlined the route and relative timing of juvenile Sockeye Salmon Oncorhynchus nerka migration by analyzing stock composition and relative CPUE in marine sampling conducted in coastal British Columbia and the Gulf of Alaska. Variation at 14 microsatellites was analyzed for 10,500 juvenile Sockeye Salmon obtained from surveys conducted during 1996–2011. Using a 404‐population baseline, we identified the sampled individuals to 47 populations or stocks of origin. Stock compositions of the mixtures increased in diversity in more northerly sampling locations, indicating a general northward movement of juveniles. The primary migration route of Columbia River and Washington stocks was northward along the west coast of Vancouver Island, with a majority of the juveniles subsequently migrating through Queen Charlotte Sound and Dixon Entrance. Fraser River stocks migrated principally through the Strait of Georgia and Johnstone Strait. Some Fraser River populations, such as the Cultus Lake population, appeared to spend little time rearing in the Strait of Georgia, as individuals from this population were primarily observed in July samples from Hecate Strait, Dixon Entrance, and Southeast Alaska. Other Fraser River populations, such as the Chilko Lake and Quesnel Lake populations, were widely distributed during July surveys, as they were observed from the Gulf of Alaska to the Strait of Georgia. For the British Columbia central coast and Owikeno Lake stocks, not all individuals migrated northward in the summer: some individuals were still present in local areas during the fall and winter after spring entry into the marine environment. Juvenile Fraser River Sockeye Salmon dominated the catch of juveniles at the Yakutat, Prince William Sound, Kodiak Island, and Alaska Peninsula sampling locations. There was a wide divergence among stocks in dispersion among sampling locations.Received September 26, 2013; accepted June 6, 2014

Late glacial and Holocene sedimentary environments of Quesnel Lake, British Columbia

At 512m Quesnel Lake is the third deepest in North America and at 100km long its drainage basin spans from the arid interior plateau to the high mountains of the eastern Cordillera where small glaciers are a significant source of sediment. In most of the lake sediment is 0 to 40m thick, reaching a maximum of just over 100m thick near the junction of the three arms. Cores from three locations in the lake provide evidence that the entire Holocene record is contained in the upper 4 to 6m of the sedimentary record where rates of accumulation have been constant or have decreased slowly. The highest rates (0.35 to 0.72mm/a) occur near points of inflow, while the lowest rate (0.22mm/a) occurs in a sheltered environment with limited inflow, and significant hypolimnic circulation which may flush water and suspended sediment from the water column. Late Pleistocene sediment beneath has a similar acoustic signature to the cored Holocene record above, suggesting that the sedimentary processes governing its deposition were not greatly different than in the present lake but that extensive glacial and paraglacial sources contributed to a significantly higher rate of accumulation. Mazama ash analyzed from two locations near points of inflow has an age of 7576±60cal. BP according to our chronology. Vivianite, which is uncommon in lakes of the Cordillera, occurs in the middle of the cores mainly associated with macroscopic wood fragments and indicates reducing conditions within the sediment.

The joint effects of riverine, thermal, and wind forcing on a temperate fjord lake: Quesnel Lake, Canada

Field data obtained in 2003–2004 are used to describe the influence of atmospheric and riverine forcing on the thermal history of fjord-type lakes using Quesnel Lake, British Columbia, Canada as an example. Typical of fjord-type lakes, Quesnel Lake is narrow, long (>100km total thalweg), multi-armed (three arms of comparable size), deep (maximum depth>500m), and has multiple basins separated by sills. The lake's annual thermal history responds to the joint forcing of surface heat exchange, river inputs, and wind stress. The lake's annual heat budget is dominated by surface radiative fluxes, and riverine input of heat is insignificant in this medium residence time lake (10years). Despite being insignificant to the annual heat budget, the three major rivers that feed the three arms of the lake contribute to the overall lake circulation pattern. Since these rivers have differing salinities, it is possible to identify, using temperature/salinity correlation diagrams, patterns of riverine circulation interflowing in the lake. Data from a 1-year thermistor-chain record suggests exchange between surface and intermediate waters occurs twice annually, but deep-waters below 150–250m are mainly renewed during autumn, by strong and episodic atmospheric forcing. This is because wind-forced turbulent diffusion and gravitational convection triggered by wind forced displacement of isotherms (initiating thermobaric instability) are required for full overturn and deep-water renewal.

The thickness of Neogene and Quaternary cover across the central Interior Plateau, British Columbia: analysis of water-well drill records and implications for mineral exploration potential1This article is one of a series of papers published in this Special Issue on the theme of New insights in Cordilleran Intermontane geoscience: reducing exploration risk in the mountain pine beetle-affected area, British Columbia. 2Geological

Analysis of over 10 000 water-well records has been used to produce new depth-to-bedrock maps for areas around five cities on the central Interior Plateau of central British Columbia: 100 Mile House, Prince George, Quesnel, Vanderhoof, and Williams Lake. Hitherto, exploration for mineral and hydrocarbon resources has been hampered by a lack of basic knowledge of the thickness of Neogene and Quaternary lithologies. Interpretation of these new maps provides first-order constraints on the localization of thick drift in pre-Late Wisconsinan bedrock paleovalleys, some of which are now buried. Basalt lavas of the Chilcotin Group are restricted to erosional remnants of previously extensive sheets emplaced onto an older peneplain. Our results confirm that the Neogene and Quaternary cover is primarily controlled by paleotopography and is generally thin and patchy across much of the region. Increased understanding of the three-dimensional distribution of cover produces a corresponding increase in the utility of geological, geochemical, and geophysical exploration techniques, and a reduction in the risk for future mineral exploration activities, especially when combined with more sophisticated data sets.

Wind-driven Summertime Upwelling in a Fjord-type Lake and its Impact on Downstream River Conditions: Quesnel Lake and River, British Columbia, Canada

Observations and modeling results are presented to explore the response of a multi-basin, fjord-type lake to episodic wind forcing. Field observations show that abrupt cooling and warming events (magnitude greater than 5°C d-1) lasting 3–6 days in a large, salmon-bearing river (Quesnel River) are due to upwelling in its upstream lake (Quesnel Lake) during the summer, stratified season. Within the lake, vertical displacement of isotherms in the vicinity of the river mouth associated with this upwelling is shown to be forced by wind events longer than one quarter of the fundamental seiche period and of sufficient magnitude that the Wedderburn number approaches one. Upwelling occurs nearly-simultaneously throughout a smaller basin adjacent to the outflow (West Basin) that is separated from the Main Basin of Quesnel Lake by a sill and contraction. Wind-driven water fluxes across the sill are estimated using a conceptual model based on volume and heat budgets. These estimates provide an upper bound for flow across the sill and suggest that exchange flow may at times be internally hydraulically controlled, with epilimnetic velocities of up to ∼25 cm/s. Computed fluxes suggest the West Basin hypolimnion has a residence time of 6-8 weeks during the summer stratified period with each upwelling episode irreversibly exchanging 25–30% of the hypolimnetic volume with the rest of the lake. Implications of such events are profound for salmon bearing rivers wherein the thermal habitat is critical to migration success.