Simulated Future Streamflow for Bow and Elbow River Basins above Calgary
A high resolution, enhanced version of Environment and Climate Change Canada’s MESH (Modélisation Environnementale Communautaire - Surface Hydrology) land surface hydrological model was set up at a spatial resolution of approximately 4 km by 4 km to correspond to the resolution of dynamically downscaled Weather Research Forecast (WRF) atmospheric model outputs for current and future climates in the region. This convection-permitting WRF product used ERA-Interim reanalysis product boundary conditions over 2000 - 2015 to produce realistic, high resolution weather simulations. The pseudo global warming (PGW) approach to dynamical downscaling of future warming projection under RCP8.5 (2086 - 2100), used WRF bounded by ERA-Interim outputs that were perturbed by the mean outcomes of an ensemble of Coupled Model Intercomparison Project Phase 5 (CMIP5) climate model projections.
Available land surface data consist of digital elevation models (DEMs), i.e. the hydrologically conditioned HydroSheds DEM that has a spatial resolution of approximately 90 m available at (
https://www.mrlc.gov/downloads/sciweb1/shared/hydrosheds), and its derived products including flow direction and drainage density. Soil data was collected from a rasterized version of the Soil Landscapes of Canada (SLC) dataset (
https://open.canada.ca/data/en/dataset). The dataset covers Canada at 90 m spatial resolution and is derived from original data at a scale of 1:1M. This dataset has some missing information for the Bow River Basin, for instance there is no information on the percentages of clay and sand of the first soil layer (0 – 5 cm depth). Landcover data was downloaded from the Commission for Environmental Cooperation (CEC) (
http://www.cec.org/north-american-land-change-monitoring-system/) covering all of the North America at a resolution of 30 m with 19 land cover classes. The Randolph Glacier Inventory 6.0 data (
https://www.glims.org/RGI/rgi60_dl.html), based on Landsat imagery from 2004–06, were used to delineate glacier coverage in the basin. The inventory was generated and manually checked in 2008 (Bolch et al., 2010).
Prior to this project, MESH, did not consider the impact of slope and elevation on meteorological forcings below the resolution of the data, which is not a reasonable assumption in mountains. Here, incoming solar radiation was calculated as a function of terrain slope and aspect. Also, precipitation, temperature, pressure, humidity, and longwave radiation were corrected for elevation. The necessary cold regions processes (blowing snow, intercepted snow, sublimation, frozen soil infiltration, slope/aspect impacts on melt rates, glacier ice melt) and water management processes needed to simulate the natural and reservoir-managed streamflow hydrographs in the basin were modelled. Most model parameter values were set based on remote sensing, land surveys and the results and understandings from previous regional hydrological investigations, however forest root depth and stomatal resistance, and soil hydraulic conductivity and channel routing model parameters were calibrated using measured (2006 - 2015) streamflows on the Bow River at Banff, and evaluated (2000 - 2005) at the same stream gauging station.
Project Title: Diagnosis of Historical and Future Flow Regimes of the Bow River at Calgary using a Dynamically Downscaled Climate Model and a Physically Based Land Surface Hydrological Model
The project assesses the impacts of projected climate change on the hydrology, including the flood frequencies, of the Bow and Elbow Rivers above Calgary, Alberta. It reports on investigations of the effects of projected climate change on the runoff mechanisms for the Bow and Elbow River basins, which are important mountain headwaters in Alberta, Canada. The study developed a methodology and applied a case study for incorporating climate change into flood frequency estimates that can be applied to a variety of river basins across Canada. It also produced model simulated future streamflow for Bow and Elbow River basins above Calgary. The project was carried out by scientists from the University of Saskatchewan Centre for Hydrology, under contract to Natural Resources Canada and Alberta Environment and Parks with contributions from the City of Calgary, Environment and Climate Change Canada and the Global Water Futures program.
Purpose: Natural Resources Canada and Public Safety Canada have established a Technical Subcommittee on Climate Change and Floodplain Mapping which has noted the challenges in floodplain mapping under non-stationarity due to the impacts of a changing climate on hydrology. The Technical Subcommittee is interested in a case study of the impacts of climate change on the hydrological regime and flooding on the Bow River at Calgary. This study would feed into other research and development of updated hydraulic modelling of the river and thus lead to a reduction in uncertainty for floodplain delineation in a time of changing climate.
Objective: This study aims to estimate the changes in flood frequency of the Bow River at Calgary over the historical period and into future climates of the 21stCentury using dynamically downscaled coupled atmospheric-hydrological models.
The dataset provides model simulated future streamflow of Bow and Elbow River basins using high resolution Weather Research Forecasting simulated historical and future climate.
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