Spatial and temporal characteristics in streamflow-related hydroclimatic variables over western Canada. Part 2: future projections (original) (raw)
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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...
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.
Assessing Climatic Drivers of Spring Mean and Annual Maximum Flows in Western Canadian River Basins
Water
Flows originating from cold and mountainous watersheds are highly dependent on temperature and precipitation patterns, and the resulting snow accumulation and melt conditions, affecting the magnitude and timing of annual peak flows. This study applied a multiple linear regression (MLR) modelling framework to investigate spatial variations and relative importance of hydroclimatic drivers of annual maximum flows (AMF) and mean spring flows (MAMJflow) in 25 river basins across western Canada. The results show that basin average maximum snow water equivalent (SWEmax), April 1st SWE and spring precipitation (MAMJprc) are the most important predictors of both AMF and MAMJflow, with the proportion of explained variance averaging 51.7%, 44.0% and 33.5%, respectively. The MLR models’ abilities to project future changes in AMF and MAMJflow in response to changes to the hydroclimatic controls are also examined using the Canadian Regional Climate Model (CanRCM4) output for RCP 4.5 and RCP8.5 sc...
Climate change impacts on snow and streamflow drought regimes in four ecoregions of British Columbia
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In many regions with seasonal snow cover, summer streamflow is primarily sustained by groundwater that is recharged during the snowmelt period. Therefore, below-normal snowpack (snow drought) may lead to below-normal summer streamflow (streamflow drought). Summer streamflow is important for supplying human needs and sustaining ecosystems. Climate change impacts on snow have been widely studied, but the relationship between snow drought and streamflow drought is not well understood. In this study, a combined investigation of climate change impacts on snow drought and streamflow drought was completed using generic groundwatersurface water models for four headwater catchments in different ecoregions of British Columbia. Results show that, in response to increased precipitation and temperature, the snow drought regime changes substantially for all four catchments. Warm snow droughts, which are caused by above-normal winter temperatures, increase in frequency, and dry snow droughts, which are caused by below-normal winter precipitation, decrease in frequency. The shift toward more frequent and severe temperature-related snow droughts leads to decreased summer runoff, decreased summer groundwater storage, and more extreme low flows in summer. Moreover, snow droughts propagate into summer streamflow droughts more frequently in the future time periods (2050s, 2080s) as compared to the baseline 1980s period. Thus, warm snow droughts not only become more frequent and severe in the future but also more likely to result in summer streamflow drought conditions.
Sustainability, 2018
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Recent Variations in Climate and Hydrology in Canada
Canadian Water Resources Journal, 2000
Climatic and hydrologic variations between the decades 1976-1985 and 1986-95 are examined at 210 climate stations for temperature,2Tl climate stations for precipitation, and 642 hydrology stations from across Canada. The variations in climate are distributed across a broad spatial area. Temperatures were generally warmer in the more recent decade, with many stations showing significant increases during spring and fall. Significant decreases in temperature were found during winter in eastern Canada. Significant increases in temperature were more frequent in western Canada than in the east. Significant decreases in precipitation were also more prevalent in the north, as were increases in the south, except for Ontario and Quebec where little or no change has taken place. The hydrologic responses to these variations in climate are classified into four hydrograph types and six patterns of shifts in streamflow between the two decades. The 642 hydrologic stations fall into pr6cipitations dtaient dgalement plus courantes dans le Nord, tout comme l'6taient Ies hausses dans le Sud, sauf en Ontario et au Qudbec, oil l'on a enregistrd que tEnvironment Canada, Vancouver, BC
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...
Hydrological Processes
The South Saskatchewan River Basin of southern Alberta drains the transboundary central Rocky Mountains region and provides the focus for irrigation agriculture in Canada. Following extensive development, two tributaries, the Oldman and Bow Rivers, were closed for further water allocations, while the Red Deer River (RDR) remains open. The RDR basin is at the northern limit of the North American Great Plains and may be suitable for agricultural expansion with a warming climate. To consider irrigation development and ecological impacts, it is important to understand the regional hydrologic consequences of climate change. To analyze historic trends that could extend into the future, we developed century-long discharge records for the RDR, by coordinating data across hydrometric gauges, estimating annual flows from seasonal records, and undertaking flow naturalization to compensate for river regulation. Analyses indicated some coordination with the Pacific Decadal Oscillation and slight decline in summer and annual flows from 1912 to 2016 (-0.13%/year, Sen's slope). Another forecasting approach involved regional downscaling from the global circulation models (GCMs), CGCMI-A, ECHAM4, HadCM3, and NCAR-CCM3. These projected slight flow decreases from the mountain headwaters versus increases from the foothills and boreal regions, resulting in a slight increase in overall river flows (+0.1%/year). Prior projections from these and other GCMs ranged from slight decrease to slight increase and the average projection of-0.05%/year approached the empirical trend. Assessments of other rivers draining the central and northern Rocky Mountains revealed a geographic transition in flow patterns over the past century. Flows from the rivers in Southern Alberta declined (around-0.15%/year), in contrast to increasing flows in northeastern British Columbia and the Yukon. The RDR watershed approaches this transition and this study thus revealed regional differentiation in the hydrological consequences from climate change.
Hydrologic effects of climatic change in west-central Canada
Journal of Hydrology, 1994
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