Kootenay Lake Research Articles

Kootenay Lake kokanee (Oncorhynchus nerka) collapse into a predator pit

Kootenay Lake is a large, oligotrophic waterbody in southern British Columbia renowned for recreational fisheries for piscivorous rainbow trout (Oncorhynchus mykiss) and bull trout (Salvelinus confluentus). Long-term datasets showed an increase in large-bodied (>2 kg) piscivore abundance followed by a collapse of the kokanee (Oncorhynchus nerka) prey population in 2013 and subsequent decline of large-bodied piscivores. An unprecedented post-collapse state formed in 2015–2018, characterized by low kokanee spawner abundance and biomass and high catch rates for small-bodied (<2 kg), slow-growing piscivores. Bioenergetics model estimates of average historical (1961–2008) piscivore consumption was 29.3% of the average historical (1993–2008) kokanee prey supply (biomass and production), but increased to 78.7% in 2011, immediately preceding kokanee collapse. From 2015–2018, kokanee did not recover due to persistently poor juvenile survival; estimated piscivore consumption relative to prey supply remained high (73.0%), suggesting that kokanee were trapped in a predator pit. Although the ultimate and interacting causes of the predator build up remain uncertain, overcoming current depensatory dynamics may be aided by kokanee stocking or increasing harvest on still-abundant, unsatiated piscivores.

Growth genes are implicated in the evolutionary divergence of sympatric piscivorous and insectivorous rainbow trout (Oncorhynchus mykiss)

BackgroundIdentifying ecologically significant phenotypic traits and the genomic mechanisms that underly them are crucial steps in understanding traits associated with population divergence. We used genome-wide data to identify genomic regions associated with key traits that distinguish two ecomorphs of rainbow trout (Oncorhynchus mykiss)—insectivores and piscivores—that coexist for the non-breeding portion of the year in Kootenay Lake, southeastern British Columbia. “Gerrards” are large-bodied, rapidly growing piscivores with high metabolic rates that spawn north of Kootenay Lake in the Lardeau River, in contrast to the insectivorous populations that are on average smaller in body size, with lower growth and metabolic rates, mainly forage on aquatic insects, and spawn in tributaries immediately surrounding Kootenay Lake. We used pool-seq data representing ~ 60% of the genome and 80 fish per population to assess the level of genomic divergence between ecomorphs and to identify and interrogate loci that may play functional or selective roles in their divergence.ResultsGenomic divergence was high between sympatric insectivores and piscivores (F_{text{ST}} = 0.188), and in fact higher than between insectivorous populations from Kootenay Lake and the Blackwater River (F_{text{ST}} = 0.159) that are > 500 km apart. A window-based F_{text{ST}} analysis did not reveal “islands” of genomic differentiation; however, the window with highest F_{text{ST}} estimate did include a gene associated with insulin secretion. Although we explored the use of the “Local score” approach to identify genomic outlier regions, this method was ultimately not used because simulations revealed a high false discovery rate (~ 20%). Gene ontology (GO) analysis identified several growth processes as enriched in genes occurring in the ~ 200 most divergent genomic windows, indicating many loci of small effect involved in growth and growth-related metabolic processes are associated with the divergence of these ecomorphs.ConclusionOur results reveal a high degree of genomic differentiation between piscivorous and insectivorous populations and indicate that the large body piscivorous phenotype is likely not due to one or a few loci of large effect. Rather, the piscivore phenotype may be controlled by several loci of small effect, thus highlighting the power of whole-genome resequencing in identifying genomic regions underlying population-level phenotypic divergences.

Characterizing the phytoplankton and zooplankton communities in Kootenay Lake: a time series analysis of 24 years of nutrient addition

Large-scale seasonal addition of limiting nutrients has been used for restoration in Kootenay Lake, British Columbia, since 1992 to mitigate cultural oligotrophication resulting from upstream hydropower development, river channelization, mysid shrimp introduction, and extensive tributary floodplain loss. Historical (1949) in-lake nutrient levels were targeted to stimulate bottom-up carbon transfer from native plankton communities to planktivorous and piscivorous fish populations that support popular fisheries. Analysis of 24 years of monitoring data assessed the effects of nutrient addition on the phytoplankton and zooplankton communities. Assessment involved comparisons of plankton community metric data from North Arm (1992–2003) and North + South arms (2004–2015) nutrient addition periods. A before–after, control–impact (BACI) analysis adjusted for these effects involved a series of phytoplankton and zooplankton metrics across the two lake arms. Time series analyses revealed significant serial correlation structure, significant increases in phytoplankton and zooplankton abundance and biomass, and increased stability within the phytoplankton and zooplankton communities. Results confirmed that adaptively managed nutrient restoration can effectively restore biological productivity and community structure in a large culturally oligotrophic lake.

Dynamic analysis of the 2012 Johnsons Landing landslide at Kootenay Lake, British Columbia: the importance of undrained flow potential

The Johnsons Landing landslide occurred on 12 July 2012 on the shores of Kootenay Lake, British Columbia. The landslide consisted of poorly sorted, low-plasticity debris that initially descended a steep channel, before avulsing onto a glaciofluvial terrace. This event destroyed three homes and killed four people who lived on this terrace. This paper presents a back-analysis of this event using numerical runout modelling. It is shown that undrained flow can explain the observed channel avulsion with fewer model parameters than needed by previous analyses. This mechanism should be considered in similar settings, as ignoring it can lead to underestimation of runup and overtopping of natural and anthropogenic flow obstacles, such as landslide protection structures.

Genetic mixture analyses in support of restoration of a high value recreational fishery for rainbow trout (Oncorhynchus mykiss) from a large lake in interior British Columbia

Genetic mixture analysis is an important tool to apportion catch amongst potential component populations contributing to a fishery. We used variation at 10 microsatellite DNA loci to assess the level of genetic divergence between two ecotypes of rainbow trout (Oncorhynchus mykiss) that naturally co-occur in Kootenay Lake, southeastern British Columbia, and to exploit such divergence in a mixture analysis. One form, “Gerrard” rainbow trout, historically matured at sizes greater than 60 cm and 5 kg, spawns at a lake outlet after upstream migration in a large river tributary to Kootenay Lake, and is highly prized in the recreational fishery. The other form, “non-Gerrard” rainbow trout, is also native to the lake and matures at smaller sizes and spawns in numerous small streams tributary to Kootenay Lake. Recent declines in growth rate of Gerrard rainbow trout, however, has made them difficult to identify by size in fishery samples. Gerrard (N = 130, 6 sites) and non-Gerrard trout N = 312, 15 sites) were highly divergent from one another (FST = 0.14, P < 0.001) and constituted distinct genetic groups in model-based clustering analyses. Genetic mixture analyses of fishery samples indicated a high degree of accuracy in estimating mixture proportions; 100% Gerrard simulated fisheries were estimated to contain 99.9% Gerrards (95% confidence intervals of 99.8–100%) while 100% non-Gerrard rainbow trout simulated fisheries were estimated to contain 100.0% non-Gerrard trout (100–100%). Across eight fishery creel samples obtained between 2015 and 2017 (N = 527 fish), mixture analysis estimated the fishery to contain an average of 73.4% (95% confidence interval = 68.4–74.6%) Gerrard and 26.6% (23.4–31.6%) non-Gerrard trout. Realistic fishery simulations demonstrated strong agreement with empirical results; the average simulated values for Gerrards was 73.4% (65.9–80.0%) and for non-Gerrards was 26.8% (20.0–34.1%). Assignment tests resulted in an average 98.5% (± 0.066%) assignment confidence; 385 fish from the fishery samples were assigned to the Gerrard group (0.73) and 142 (0.27) to the non-Gerrard rainbow trout genetic group. Fitting length-at-age data for genetically assigned fishery samples to a von Bertalanffy growth model found greatest support for a model employing ecotype-specific L∞ (= 59.6 and 52.9 cm for Gerrards and non-Gerrards, respectively, both P < 0.001), and t0 (= − 1.36 and − 2.58, respectively, both P < 0.05), but a common K (= 0.189, P < 0.001). Our mixture analyses are being used to monitor catches and better understand the feeding and migration biology of these sympatric ecotypes of rainbow trout.

Population structure of sea-type and lake-type sockeye salmon and kokanee in the Fraser River and Columbia River drainages.

Population structure of three ecotypes of Oncorhynchus nerka (sea-type Sockeye Salmon, lake-type Sockeye Salmon, and Kokanee) in the Fraser River and Columbia River drainages was examined with microsatellite variation, with the main focus as to whether Kokanee population structure within the Fraser River drainage suggested either a monophyletic or polyphyletic origin of the ecotype within the drainage. Variation at 14 microsatellite loci was surveyed for sea-type and lake-type Sockeye Salmon and Kokanee sampled from 121 populations in the two river drainages. An index of genetic differentiation, FST, over all populations and loci was 0.087, with individual locus values ranging from 0.031 to 0.172. Standardized to an ecotype sample size of 275 individuals, the least genetically diverse ecotype was sea-type Sockeye Salmon with 203 alleles, whereas Kokanee displayed the greatest number of alleles (260 alleles), with lake-type Sockeye Salmon intermediate (241 alleles). Kokanee populations from the Columbia River drainage (Okanagan Lake, Kootenay Lake), the South Thompson River (a major Fraser River tributary) drainage populations, and the mid-Fraser River populations all clustered together in a neighbor-joining analysis, indicative of a monophyletic origin of the Kokanee ecotype in these regions, likely reflecting the origin of salmon radiating from a refuge after the last glaciation period. However, upstream of the mid-Fraser River populations, there were closer relationships between the lake-type Sockeye Salmon ecotype and the Kokanee ecotype, indicative of the Kokanee ecotype evolving independently from the lake-type Sockeye Salmon ecotype in parallel radiation. Kokanee population structure within the entire Fraser River drainage suggested a polyphyletic origin of the ecotype within the drainage. Studies employing geographically restricted population sampling may not outline accurately the phylogenetic history of salmonid ecotypes.

The fishing and natural mortality of large, piscivorous Bull Trout and Rainbow Trout in Kootenay Lake, British Columbia (2008-2013).

BackgroundEstimates of fishing and natural mortality are important for understanding, and ultimately managing, commercial and recreational fisheries. High reward tags with fixed station acoustic telemetry provides a promising approach to monitoring mortality rates in large lake recreational fisheries. Kootenay Lake is a large lake which supports an important recreational fishery for large Bull Trout and Rainbow Trout.MethodsBetween 2008 and 2013, 88 large (≥500 mm) Bull Trout and 149 large (≥500 mm) Rainbow Trout were marked with an acoustic transmitter and/or high reward ($100) anchor tags in Kootenay Lake. The subsequent detections and angler recaptures were analysed using a Bayesian individual state-space Cormack–Jolly–Seber (CJS) survival model with indicator variable selection.ResultsThe final CJS survival model estimated that the annual interval probability of being recaptured by an angler was 0.17 (95% CRI [0.11–0.23]) for Bull Trout and 0.14 (95% CRI [0.09–0.19]) for Rainbow Trout. The annual interval survival probability for Bull Trout was estimated to have declined from 0.91 (95% CRI [0.76–0.97]) in 2009 to just 0.46 (95% CRI [0.24–0.76]) in 2013. Rainbow Trout survival was most strongly affected by spawning. The annual interval survival probability was 0.77 (95% CRI [0.68–0.85]) for a non-spawning Rainbow Trout compared to 0.41 (95% CRI [0.30–0.53]) for a spawner. The probability of spawning increased with the fork length for both species and decreased over the course of the study for Rainbow Trout.DiscussionFishing mortality was relatively low and constant while natural mortality was relatively high and variable. The results indicate that angler effort is not the primary driver of short-term population fluctations in the Rainbow Trout abundance. Variation in the probability of Rainbow Trout spawning suggests that the spring escapement at the outflow of Trout Lake may be a less reliable index of abundance than previously assumed. Multi-species stock assessment models need to account for the fact that large Bull Trout are more abundant than large Rainbow Trout in Kootenay Lake.

Evaluating the influence of predator–prey interactions on stock assessment and management reference points for a large lake ecosystem

Ecosystem models are thought to offer advantages over single-species models in terms of management policy analysis. This hypothesis has proven difficult to test because of underlying system complexities, coupled with short time series and minimal contrast in environmental conditions or management policies. This paper presents a Bayesian statistical catch-at-age model to compare ecosystem models and test hypotheses about the management of a recreational fishery based on a predator–prey system using a relatively simple and data-rich ecosystem in a large lake, Kootenay Lake, British Columbia, where kokanee (Oncorhynchus nerka) are the prey and piscivorous rainbow trout (Oncorhynchus mykiss) are the predator. A model that explicitly incorporates the predator–prey interaction explained long-term data of field and fishery surveys much better than single-species models without any interactions. Minimally realistic multispecies models that treated predation identically but differed in their representation of the effects of prey abundance on predator mortality produced quite different results. Management reference points, for example, differed considerably between the models. Our study thus emphasizes that the choice of a management approach for this type of fishery will depend strongly on the model form and should take into consideration results from empirically based models that include species interactions.

Adjusting for undercoverage of access-points in creel surveys with fewer overflights.

Creel surveys are used in recreational fisheries to estimate angling effort, catch, and harvest. Aerial-access creel surveys rely on two components: (1) a ground component in which fishing parties returning from their trips are interviewed at some access-points of the fishery; (2) an aerial component in which the number of fishing parties is counted. A common practice is to sample fewer aerial survey days than ground survey days. This is thought by practitioners to reduce the cost of the survey, but there is a lack of sound statistical methodology for this case. In this article, we propose various estimation methods to handle this situation and evaluate their asymptotic properties from a design-based perspective. We also propose formulas for the optimal allocation of the effort between the ground and the aerial portion of the survey, for given costs and budget. A simulation study investigates the performance of the estimators. Finally, we apply our methods to data from an annual Kootenay Lake survey (Canada).

Adaptation of lake-origin burbot stocked into a large river environment

Burbot Lota lota maculosa numbers in Kootenay Lake and Kootenai River of British Columbia, Idaho, and Montana have diminished due to habitat changes from the construction of Libby Dam. Recent implementation of a conservation strategy included aquaculture to supplement the population using a donor stock from a self-sustaining lake population within the watershed. Evaluation of release strategies using telemetry and mark recapture through hoop netting suggests lake-origin Burbot have adapted to the Kootenai system and selected riverine over lacustrine habitat. Previous telemetry work identified good survival and dispersal of released Burbot, and vast dispersal distance and lacustrine use. However, our analysis of a broader telemetry dataset indicated that only 24% of age 1–4 Burbot were detected in the lake. Recapture hoop net data indicated that Burbot residing in the river have growth and survival rates comparable to the historical population. Spawning of hatchery origin fish was detected at historical riverine spawning locations. Other than later spawn timing, our evaluations suggest lake-origin fish are mimicking movement and habitat use of the historical riverine population. This study, in combination with others, provides evidence that Burbot progeny from lacustrine brood stock can successfully survive, grow, disperse, and spawn in a riverine environment.

Ideological Migration and War Resistance in British Columbia’s West Kootenays: An Analysis of Counterculture Politics and Community Networks among Doukhobor, Quaker, and American Migrants during the Vietnam War Era

This paper addresses migration, war resistance, and counterculture activity in the West Kootenays region of British Columbia during the 1960s and 1970s. Through a combination of perspectives including S.N. Eisenstadt’s discussion of “multiple modernities,” it reveals an ongoing pattern of alternative, values-based migration we refer to as “ideological migration.” Most immediately associated with the influx of thousands of young Americans who came to the West Kootenays during the Vietnam War, this pattern, in fact, began much earlier, first with the arrival of the Doukhobors beginning in 1908, and subsequently in the 1950s with the development of a community of American Quakers at the north end of Kootenay Lake. From there, we show how common experiences of marginalization along with with shared values of pacifism, war resistance, community-building, and self-sufficiency facilitated the arrival of this new group, and with them the entrenchment in the region of a vibrant counterculture identity.

Effects of long-term protection from grazing on phenotypic expression in geographically separated mountain rough fescue populations

Thompson, D. J. and Willms, W. D. 2014. Effects of long-term protection from grazing on phenotypic expression in geographically separated mountain rough fescue populations. Can. J. Plant Sci. 94: 33–39. Whether or not long-term grazing or protection from grazing alters the genetic makeup of grass populations has been debated. Mountain rough fescue [(Festuca campestris (Rydb.)], which is highly sensitive to summer grazing, and becomes dominant in plant communities with long-term protection, was chosen to address this question. Plants from three geographic sites (Stavely in AB, Milroy in the Kootenay trench, BC and Goose Lake on the BC interior plateau) with divergent grazing histories were vegetatively propagated from tillers. Daughter plants were planted into two field nurseries (at Kamloops, BC, and Stavely, AB) and morphological measurements were taken in two field seasons post-establishment. Plants from all three populations were taller, flowered earlier, and were more productive at the Kamloops nursery site. Of the three geographic sources, plants from the Goose Lake site were most distinct with narrower leaves, later flowering, and greater yield. Plants with a long history of grazing had slightly shorter fertile tillers and leaves than plants with a history of long-term protection.

Survival and Dispersal of Sonic‐Tagged, Hatchery‐Reared Burbot Released into the Kootenay River

AbstractAs part of recovery efforts for the Kootenay population of Burbot Lota lota, we monitored 109 sonic‐tagged, hatchery‐reared Burbot released at 1–3 years of age throughout Kootenay Lake and the Kootenay River over a 3‐year period. Our objectives were to evaluate broodstock choice, assess differences in survival and dispersal by release site and age, and evaluate spawning movements. Overall, release survival was high (66%) and there was dispersal throughout the system (up to 235 km), involving both lacustrine and riverine habitat. Spawning movements were extensive (up to 59 km/d upstream) and suggest the use of known spawning locations. However, most age‐1 releases had lower survival and remained in the release tributaries for 1 year postrelease, which was longer than expected and which warrants further investigation. Overall, this telemetry study provides a positive outlook on the current aquaculture rehabilitation efforts for Kootenay Burbot and provides direction for further work.

A Synthesis of Kootenai River Burbot Stock History and Future Management Goals

AbstractIn Idaho, Burbot Lota lota are endemic only to the Kootenai River, where they once provided an important winter fishery to the indigenous people and European settlers. This fishery and that of Kootenay Lake in British Columbia may have been the most robust Burbot fisheries in North America. However, the fishery in Idaho rapidly declined after the construction of Libby Dam by the U.S. Army Corps of Engineers in 1972, and it closed in 1992. Concomitant to the collapse in Idaho was the collapse of the Burbot fishery in Kootenay Lake and the Kootenay River. The operation of Libby Dam for hydroelectric power generation and flood control created major changes in the river's nutrient concentration, temperature, and seasonal discharge, particularly during the winter when Burbot spawn. Libby Dam operations were implicated as the major limiting factor to Burbot recruitment, giving rise to higher winter temperatures and widely fluctuating flows. Because the Burbot in the Kootenai River are at risk of demographic extinction, a conservation strategy was prepared to outline the measures necessary to rehabilitate the Burbot population to a self‐sustaining level. The strategy indicated that operational discharge changes at Libby Dam are required during winter to provide suitable temperature and discharge conditions for Burbot migration and spawning. Studies recommend that the discharge at Bonners Ferry average 176 m3/s for a minimum of 90 d (mid‐November through mid‐February). Furthermore, preferred Burbot water temperatures of about 6°C are necessary for migration and cooler temperatures of 1–4°C for spawning. With each passing year, Burbot stock limitations increasingly constrain rehabilitation. Thus, coordination of intensive culture, extensive rearing, and pen rearing among the Kootenai Tribe of Idaho, the British Columbia Ministry of Environment, the University of Idaho's Aquatic Research Institute, and the Idaho Department of Fish and Game is important for restoration.

Neutral Loci Reveal Population Structure by Geography, not Ecotype, in Kootenay Lake Kokanee

Abstract Genetic tools are often used to define stocks for fisheries management, however, traditional approaches using neutral markers may be inadequate for detecting fine-scale structure when populations have recently diverged. Kokanee Oncorhynchus nerka is a freshwater form of sockeye salmon that exhibits divergent reproductive ecotypes. We used a combination of expressed sequence tag (EST)-linked and non-EST-linked microsatellites to investigate kokanee stock structure and ecotype differentiation in Kootenay Lake, British Columbia. Despite being highly informative in other lakes in the province, the EST-linked loci used in this study did not exhibit outlier behavior relative to neutral loci for distinguishing shore-spawning and stream-spawning ecotypes. We found conflicting evidence for differentiation between ecotypes and strong evidence for geographical structure corresponding to the North Arm and West Arm of Kootenay Lake. These results are consistent with previous findings that neutral markers are ...

CMA president-elect traverses wildernesses

Dr. Anna Reid thought she was done with all things political. Back at Kootenay Lake Hospital in Nelson, British Columbia, she had served as chief of staff, as chair of the quality assurance committee and as president and chair of the medical advisory committee. It had been difficult at times. She

THE ORIGIN OF MINERALIZED FRACTURES AT THE BLUEBELL MINE SITE, RIONDEL, BRITISH COLUMBIA

The Bluebell Pb-Zn deposit is located on the east side of Kootenay Lake in southeastern British Columbia. It is a fracture-controlled replacement deposit hosted in Lower Cambrian marble of the Badshot and Mohican formations. The orebodies trend west-northwest, parallel to a prominent set of fractures that controlled mineralization. These fractures are interpreted to have formed as part of a conjugate set. Contrary to some earlier suggestions, folding played no role in fracture formation. The youngest generation of folds are reinterpreted as having formed through development of shear bands during extension of the layering prior to fracture development. Formation of the fractures also postdated motion on a number of early Tertiary normal faults that are associated with regional extension and alkaline magmatism. West-northwest–trending fractures, which formed as part of a conjugate set, were reactivated and controlled the intrusion of mafic dikes, mineralizing fluids, and minor late faulting. Fracturing, faulting, mafic dike intrusion, and mineralization may be associated with a long-lived basement structure that runs below the area, which could have facilitated the ascent of deep crustal or mantle-derived magma and mineralizing fluids. The results of this study provide a new perspective on exploration strategies for hydrothermal ore deposits in this part of southeastern British Columbia.

Bull trout (Salvelinus confluentus) movement in a transboundary river

The bull trout (Salvelinus confluentus) is listed as a threatened species and is native to the Kootenai River, Idaho and Montana, USA, and British Columbia (BC), Canada. Little is known about its life history and movements downstream of Kootenai Falls, Montana. Between 1998 and 2006, 19 bull trout were monitored in the Kootenai River with radio and sonic transmitters. Two bull trout life history patterns were found; 16 bull trout were likely fluvial, and two were adfluvial. Evidence of spawning was found for only about 33% of the bull trout tracked; of those, 50% were annual spawners and 50% alternate-year spawners. Temperature of the Kootenai River during spawning migration of six bull trout that made spawning migrations ranged from 7.1°C to 15.0°C and averaged 11.4°C. Telemetry data indicated nine bull trout concentrated below Kootenai Falls during the spawning season, but it is not known if they spawned. Two tagged bull trout were located in Kootenay Lake, BC. One fish returned to the river and moved a total of 228 km from Kootenay Lake through Idaho and to Kootenai Falls. Bull trout also used several tributary streams outside of the spawning season, possibly as a thermal refuge.

Movement of Lake‐Origin Burbot Reared in a Hatchery Environment and Released into a Large River Drainage

AbstractBurbot Lota lota in Kootenay Lake and the Kootenay River of British Columbia, Idaho, and Montana (U.S. spelling: “Kootenai River”) are at risk of demographic extinction. We conducted a pilot study to evaluate poststocking dispersal and movement of hatchery‐reared, lake‐strain burbot (Moyie Lake, British Columbia) in a riverine environment to determine the potential utility of this hatchery strain for future burbot rehabilitation efforts in this system. We implanted ultrasonic tags into 30 hatchery‐reared burbot (ages 2 and 3) and released them into the Goat River, a tributary to the Kootenay River, in October 2009. Dispersal over a distance of 2 km from the Goat River release site to the Kootenay River occurred within 1–9 d after release (mean = 3.1 d; n = 28 active tags). Thereafter, 14 burbot remained in the Kootenay River for the rest of the 144‐d study period; nine of these fish were observed moving upstream from the Goat River confluence, and five were observed both upstream and downstream from the confluence. The other 14 burbot were observed in Kootenay Lake; of these fish, eight were detected in the lake for the duration of the study, and six were observed to move regularly between the lake and the river. Dispersal distances (distance between the upstream‐most and downstream‐most detections per individual) within the Kootenay River ranged from 10 to 138 km (mean = 80 km), and tagged fish were detected over a 236‐km reach (from 135 km downstream to 101 km upstream of the Goat River confluence). We also observed burbot in the vicinity of known spawning locations during the February spawning season. The observed dispersal suggests that a limited number of stocking locations may be sufficient to allow burbot to access available habitats within a few months postrelease. Our observations therefore suggest that lake‐origin, hatchery‐reared burbot may be suitable for stocking in a riverine environment.Received June 11, 2010; accepted December 4, 2010

Daily Time-Step Refinement of Optimized Flood Control Rule Curves for a Global Warming Scenario

Pacific Northwest temperatures have warmed by 0.8°C since 1920 and are predicted to increase in the 21st century. Streamflow timing shifts associated with climate change would degrade the water resources system performance for climate change scenarios using existing system operation policies for the Columbia River Basin. To mitigate the hydrologic impacts of anticipated climate change on this complex water resource system, optimized flood control operating rule curves were developed at a monthly time step in a previous study and were evaluated with a monthly time-step simulation model. Here, a daily time-step simulation model is used over a smaller portion of the domain to evaluate and refine the optimized flood-control curves derived from monthly time-step analysis. Daily time-step simulations demonstrate that maximum evacuation targets for flood control derived from the monthly analysis were remarkably robust. However, the evacuation schedules for Libby and Duncan Dams from February to April conflicted with Kootenay Lake level requirements specified in the 1938 International Joint Commission Order on Kootenay Lake. We refined the flood rule curves derived from monthly analysis by creating a gradual evacuation schedule, keeping the timing and magnitude of maximum evacuation the same as in the monthly analysis. After these refinements, the performance at monthly timescales reported in our previous study proved robust at daily timescales. Owing to a decrease in July storage deficits, additional benefits such as more revenue from hydropower generation and more July and August outflow for fish augmentation were observed when the optimized flood-control curves were used for a climate-change scenario.