Assessing Climatic Drivers of Spring Mean and Annual Maximum Flows in Western Canadian River Basins (original) (raw)
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Hydrology Research, 2016
Much of the freshwater in western Canada originates in the Rocky Mountains as snowpack. Temperature and precipitation patterns throughout the region control the amount of snow accumulated and stored throughout the winter, and the intensity and timing of melt during the spring freshet. Therefore, changes in temperature, precipitation, snow depth, and snowmelt over western Canada are examined through comparison of output from the current and future periods of a series of regional climate models for the time periods 1971–2000 and 2041–2070. Temporal and spatial analyses of these hydroclimatic variables indicate that minimum temperature is likely to increase more than maximum temperature, particularly during the cold season, possibly contributing to earlier spring melt. Precipitation is projected to increase, particularly in the north. In the coldest months of the year snow depth is expected to increase in northern areas and decrease across the rest of study area. Snowmelt results indic...
Journal of Hydrometeorology, 2022
Anthropogenic climate change-induced snowpack loss is affecting streamflow predictability, as it becomes less dependent on the initial snowpack conditions and more dependent on meteorological forecasts. We assess future changes to seasonal streamflow predictability over two large river basins, Liard and Athabasca in western Canada, by approximating streamflow response from the Variable Infiltration Capacity (VIC) hydrologic model with the Bayesian regularized neutral network (BRNN) machine learning emulator. We employ the BRNN emulator in a testbed ensemble streamflow prediction system by treating VIC-simulated snow water equivalent (SWE) as a known predictor and precipitation and temperature from GCMs as ensemble forecasts, thereby isolating the effect of SWE on streamflow predictability. We assess warm-season mean and maximum flow predictability over 2041-70 and 2071-2100 future periods against the1981-2010 historical period. The results indicate contrasting patterns of change, with the predictive skills for mean flow generally declining for the two basins, and marginally increasing or decreasing for the headwater subbasins. The predictive skill for maximum flow declines for the relatively warmer Athabasca basin and improves for the colder Liard basin and headwater subbasins. While the decreasing skill for the Athabasca is attributable to substantial loss in SWE, the improvement for the Liard and headwaters can be attributed to an earlier maximum flow timing that reduces the forecast horizon and offsets the effect of SWE loss. Overall, while the future change in SWE does affect the streamflow prediction skill, the loss of SWE alone is not a sufficient condition for the reduction in streamflow predictability. SIGNIFICANCE STATEMENT: The purpose of this study is to evaluate potential changes in seasonal streamflow predictability in relation to snowpack change under future climate. This is highly relevant because snowpack storage provides a means of predicting available freshet water supply, as well as peak flow events in cold regions. We use a machine learning model as an emulator of a hydrologic model in a testbed ensemble prediction system. Our results provide insights on hydroclimatic controls and interactions that affect future streamflow predictability across two river basins in western Canada. We conclude that besides snowpack, predictability depends on a number of other factors (basin/subbasin characteristics, streamflow variables, and future periods), and the loss of snowpack alone is not a sufficient condition for the reduction in streamflow predictability.
Climate Impacts on Hydrological Variables in the Mackenzie River Basin
Canadian Water Resources Journal, 2012
The research described in this paper examines changes in the hydrologic cycle in the Mackenzie River Basin (MRB) in northern Canada. The study focuses on temperature, precipitation, runoff, evapotranspiration and storage. A distributed hydrological model is used with two different climate input data sets: Environment Canada gridded observed data and the European Centre for Medium-range Weather Forecasting (ECMWF) reanalysis climate data (ERA-40). Both data sets were used to estimate runoff and evapotranspiration. The resulting hydrological variables were assessed for trends on a monthly and annual basis using the Mann-Kendall non-parametric trend test. The results reveal a general pattern of warming temperatures, and increasing precipitation and evapotranspiration. However, an overall decrease in runoff and in storage were detected for results derived from the Environment Canada data set while an overall increase in runoff and in storage were detected for results derived from the ECMWF data set. The sensitivity of mean annual runoff to changes in climate was also estimated using a non-parametric estimator. The results of the analysis can be used to better prepare for the potential impacts of climate change on water availability and water resource infrastructure in the MRB. Ré sumé : La recherche décrite dans la présente communication porte sur les changements dans le cycle hydrologique du bassin du fleuve Mackenzie dans le Nord du Canada. L'étude est axée sur la température, les précipitations, le ruissellement, l'évapotranspiration et l'emmagasinement. Un modèle hydrologique distribué est utilisé avec deux ensembles différents de données d'entrée climatiques : données observées sur grille d'Environnement Canada et données climatiques des réanalyses ERA-40 du Centre européen pour les prévisions météorologiques à moyen terme (CEPMMT). Les deux ensembles de données ont été utilisés afin d'estimer le ruissellement et l'évapotranspiration. Les variables hydrologiques qui en ont résulté ont été évaluées afin de dégager les tendances sur une
The impact of climate change on water availability in two river basins located in central Canada is investigated. Several statistical downscaling methods are used to generate temperature and precipitation scenarios from the third-generation Canadian Coupled General Circulation Model, forced with different emission scenarios. The hydrological model SLURP is used to simulate runoff. All downscaling methods agree that temperature will increase with time and that precipitation will also increase, although there is considerably more uncertainty in the magnitude of precipitation change. The study concludes that the change in total annual precipitation does not necessarily translate into similar changes in runoff. The seasonal distribution of precipitation changes is important for runoff, as is the increase in evapotranspiration. The choice of downscaling method appears to have a greater impact on runoff projections than the choice of emission scenario. Therefore, it is important to consider several downscaling methods when evaluating the impact of climate change on runoff.
Climatic Controls on Mean and Extreme Streamflow Changes Across the Permafrost Region of Canada
Water, 2021
Climatic change is affecting streamflow regimes of the permafrost region, altering mean and extreme streamflow conditions. In this study, we analyzed historical trends in annual mean flow (Qmean), minimum flow (Qmin), maximum flow (Qmax) and Qmax timing across 84 hydrometric stations in the permafrost region of Canada. Furthermore, we related streamflow trends with temperature and precipitation trends, and used a multiple linear regression (MLR) framework to evaluate climatic controls on streamflow components. The results revealed spatially varied trends across the region, with significantly increasing (at 10% level) Qmin for 43% of stations as the most prominent trend, and a relatively smaller number of stations with significant Qmean, Qmax and Qmax timing trends. Temperatures over both the cold and warm seasons showed significant warming for >70% of basin areas upstream of the hydrometric stations, while precipitation exhibited increases for >15% of the basins. Comparisons o...
Precipitation Trends Contribute to Streamflow Regime Shifts in Northern Canada
2011
Autumn runoff events rivalling the size of the spring freshet peak as well as sustained winter streamflow have become more common in the northwestern Canadian Shield since the mid 1990s. Previous circumpolar and large regional-scale studies have implied these phenomena are due to increased water inputs from thawing permafrost. However, results from an investigation of the precipitation and temperature trends provide an alternate explanation for this region. A shift from a nival to a combined nival/pluvial streamflow regime, particularly in small watersheds, can be attributed to trends in the timing and state of autumn precipitation. Because these trends are subtle, careful consideration of hydrological processes, and the temporal and landscape context in which they operate, is important when attempting to explain the observed shifts in regional streamflow. It is important to correctly explain why streamflow regimes are changing because of close relationships with variations in groun...
A Dynamical Climate Model-Driven Hydrologic Prediction System for the Fraser River, Canada
Journal of Hydrometeorology, 2015
Recent improvements in forecast skill of the climate system by dynamical climate models could lead to improvements in seasonal streamflow predictions. This study evaluates the hydrologic prediction skill of a dynamical climate model-driven hydrologic prediction system (CM-HPS), based on an ensemble of statistically downscaled outputs from the Canadian Seasonal to Interannual Prediction System (CanSIPS). For comparison, historical and future climate traces-driven ensemble streamflow prediction (ESP) was employed. The Variable Infiltration Capacity model (VIC) hydrologic model setup for the Fraser River basin, British Columbia, Canada, was used as a test bed for the two systems. In both cases, results revealed limited precipitation prediction skill. For streamflow prediction, the ESP approach has very limited or no correlation skill beyond the months influenced by initial hydrologic conditions, while the CM-HPS has moderately better correlation skill, attributable to the enhanced temperature prediction skill that results from CanSIPS's ability to predict El Niño-Southern Oscillation (ENSO) and its teleconnections. The root-mean-square error, bias, and categorical skills for the two methods are mostly similar. Hydrologic modeling uncertainty also affects the prediction skill, and in some cases prediction skill is constrained by hydrologic model skill. Overall, the CM-HPS shows potential for seasonal streamflow prediction, and further enhancements in climate models could potentially to lead to more skillful hydrologic predictions.
Advances in Meteorology, 2016
We compared the spatiotemporal variability of temperatures and precipitation with that of the magnitude and timing of maximum daily spring flows in the geographically adjacent L’Assomption River (agricultural) and Matawin River (forested) watersheds during the period from 1932 to 2013. With regard to spatial variability, fall, winter, and spring temperatures as well as total precipitation are higher in the agricultural watershed than in the forested one. The magnitude of maximum daily spring flows is also higher in the first watershed as compared with the second, owing to substantial runoff, given that the amount of snow that gives rise to these flows is not significantly different in the two watersheds. These flows occur early in the season in the agricultural watershed because of the relatively high temperatures. With regard to temporal variability, minimum temperatures increased over time in both watersheds. Maximum temperatures in the fall only increased in the agricultural wate...
Assessment of the influence of Nonstationary Climate on Extreme Hydrology of Southwestern Canada
2020
Knowledge of the spatial and temporal distribution of water resources is vital to address management practices and policies for planned adaptation to a changing climate. The primary objective of this study is to examine the spatial and temporal variability of available water in the naturally flowing watersheds of southwestern Canada using regional hydroclimatic indices. To do so, we first examined the empirical relationships between historically observed streamflow in 24 naturally flowing watersheds across southwestern Canada and the associated watershed’s hydroclimate, represented by the watershed averaged Standardised Precipitation Evapotranspiration Index (SPEI). The hydroclimate of all the selected watersheds is assumed to be represented by the second version of the NRCAN gridded climate dataset. We then developed SPEI-based principle component regression (PCR) equations and found them to be very efficient in representing the variability in historically observed monthly and annu...