Diagnosis of Historical and Future Hydrology of the Bow and Elbow Rivers at Calgary: A blueprint for assessing climate change impacts on flooding
Adaptation Platform Webinar December 11, 2020 Webinar Presenter
Professor John Pomeroy, PhD, FRGS, FRSC
Canada Research Chair in Water Resources and Climate Change
Distinguished Professor, Dept. of Geography & Planning
Director: • CFREF Global Water Futures Programme • USask Centre for Hydrology • USask Coldwater Laboratory, Canmore, Alberta
2 Diagnosing the Historical and Future Hydrology of the Bow and Elbow Rivers at Calgary A blueprint for assessing climate change impacts on flooding Zelalem Tesemma, Chandra Rajulapati, Kevin Shook, Dan Princz, Saman Razavi, Alain Pietroniro, Howard Wheater, Simon Papalexiou, Bruce Davison, Yanping Li and John Pomeroy Canada, we have a problem…..
• Dramatic increase in flood damages across the country since 2000 • Floodplain maps are outdated, and the historical data used to calculate them is subject to non-stationarity • How to calculate future floods? • Most hydrological models have a poor physical basis for prediction in Canada • Conceptual parameters do not work well in the future • Lack of cold regions processes impairs reliability and ability to diagnose change • Lack of water management limits “real world” simulations • Atmospheric models are needed to force hydrological models • Climate models have poor resolution and precipitation dynamics • Weather models are expensive to run for future climates Forcing Data Available For Hydrological Modelling
Forcing Inputs Full Name Record Spatial / Temporal length resolution EU-WFD-CRU European Union Integrated Project 1901 - 2001 0.5˚ / 3 and 6 hourly Water and Global Change (EU-WATCH) Forcing Data WFDEI European Union Integrated Project Water 1979 - 2016 0.5˚ / 3 hourly and Global Change (EU WATCH) ERA-Interim GEM-CaPA Global Environmental Multiscale 2002 - 2019 0.09-0.22˚ / 1 hourly and Canadian Precipitation Analysis WFDEI-GEM-CaPA Bias corrected WFDEI using GEM-CaPA 1979 - 2016 0.125˚ / 3 hourly CanRCM4-r8i2p1r1 Canadian Centre for Climate Modelling 1950 - 2100 0.125˚ / 1 hourly and Analysis Canadian Regional Climate Model CanRCM4-WFDEI Bias corrected CanRCM4 using 1950 - 2100 0.125˚ / 3 hourly -GEM-CaPA WFDEI-GEM-CaPA WRF Weather Research and Forecasting 2000 - 2015 0.05˚ / 1 hourly Weather Research and Forecasting (WRF) Model domain over Western Canada
Study domain MESH model
• Feedback with atmospheric and groundwater models • model falsification (Glaciers, blowing snow, frozen soil infiltration, slope/aspect, physical based phase change) to evaluate the necessary cold regions processes • Better discretization for mountain headwater basin • Flexible • Large river basins • water management processes needed to simulate the natural river Pietroniro et al., 2007 and reservoir- managed river hydrographs in the basin MESH model setup for Bow River at Calgary
• Model was set up at standard (10 km) resolution and a 4 km resolution consistent with WRF forcing data • Model was parameterised from • DEM 90 m for slope, aspect and drainage • Land cover 30 m (Landsat Comm. Env. Cooperation) • Soils - ECCC • Streams from ECCC - Water Survey • Managed Basin setup • with dams and reservoir storage • “Mountain Mesh” • Downscale shortwave irradiance to slopes • Downscale wind speed, air pressure, temperature, humidity, precipitation, precipitation phase to elevation • Improved glacier model in MESH, snow redistribution used Bow & Elbow Rivers above Calgary – ~10x10 km and ~4x4km MESH modelling setup Topography and Hydro-Shed DEM Slope, Aspect and Land Cover Grouped Hydrological Response Unit (GRU) Creation MESH Model Realisations: WATCH & Gem-CaPA
Calibration of subsurface storage and routing parameters from 2 GRU only. NSE objective function MESH Model Realisations: CanRCM4 (bias corr.)
Calibration of subsurface storage and routing parameters from 2 GRU only. NSE objective function MESH Bow@Banff: calibration and validation with historical WRF - 4km data
9 MESH Elbow@Sarcee: calibration and validation with historical WRF - 4km data MESH with Reservoirs, Bow@Calgary: calibration and validation with historical WRF - 4km
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WRF Pseudo-Global-Warming 2070-2099
CMIP5 1. Calculate 30-year monthly mean values of U, V, T, Qv, PSFC, Tsoil and models SST of current and future climate periods from multi CMIP5 ACCESS1-3 CanESM2 model ensemble (1976-2005 historical and 2070-2099, RCP8.5) CCSM4 CESM1-CAM5 Multi-model mean CMCC-CM Historical CNRM-CM5 Average 1976-2005 CSIRO-Mk3-6-0 Global warming GFDL-CM3 GFDL-ESM2M increments GISS-E2-H (monthly means) HadGEM2-CC HadGEM2-ES Multi-model mean Inmcm4 RCP85 IPSL-CM5A-MR Average 2070-2099 MIROC5 MIROC-ESM MPI-ESM-LR MPI-ESM-MR 2. Subtract current from future to get monthly climate perturbations MRI-CGCM3 3. Add time-interpolated perturbation to current reanalysis (ERA-Interim, 6- hourly) to give new WRF model initial and lateral boundary conditions Basin Average Precipitation
P (mm / yr) Historical Future Difference Bow River Banff 864 979 +115
Bow River Calgary 723 826 +103
Elbow River Sarcee 678 766 +88
Basin Average Temperature
T (oC / yr) Historical Future Difference
Bow River Banff -4.16 0.54 +4.70
Bow River Calgary -1.89 2.70 +4.59
Elbow River Sarcee -0.14 4.35 +4.49 CanRCM4 Climate Projections
• Dynamically downscaled to regional climate models from global circulation models • Coarser resolution than WRF • Less accurate representation of mountain weather • Representation of uncertainty from multiple realisations in model runs is possible Future Runoff for Streamflow
Glaciers Contribution (%) Basins Simulation Historical Future Future Period Period Period Runs (2001 - (2086 - (2086 - 2015) 2100) 2100) With With Without Glacier Glacier Glacier Bow River WRF - 2.4 9.3 0 at Banff Mountain MESH CanRCM4 - 13.5 25 0 Mountain MESH Bow River WRF - 1.8 6.3 0 at Calgary Mountain MESH CanRCM4 - 9.5 16.7 0 Mountain MESH Future Streamflow Regimes
Bow@Banff Future Streamflow Regimes
Bow@ Calgary Future Streamflow Regimes
Elbow below Glenmore Reservoir Diagnosis of the 2013 high flow events in more detail June 2013 current and future climate runoff mechanisms
WRF-MESH Calculation of future streamflow exceedance probabilities for flood risk estimation Future Flow Duration Curves WRF-MESH
Bias corrected to historical streamflow from WSC Future Flow Duration Curves CanRCM4- MESH
Bias corrected to historical streamflow from WSC Predicted Changes in Quantiles
% Time Flow QObs WRF-MESH WRF-MESH % Change CanRCM4-MESH CanRCM4-MESH % Change
Equalled / QSHist QSFutu QSHist QSFutu Exceeded Bow River at Banff 10 97.6 97.6 83.3 -14.7 97.7 65.0 -33.4 20 62.5 62.5 54.5 -12.9 62.5 39.9 -36.2 30 40.3 40.4 39.6 -2.0 40.5 29.3 -27.6 40 26.7 26.7 32.5 21.7 26.7 24.0 -10.3 50 17.0 16.9 29.6 74.9 16.9 21.4 26.8 60 11.8 11.7 27.4 134.0 11.7 18.5 57.7 70 9.8 9.8 24.9 155.7 9.8 15.9 63.2 80 8.8 8.8 23.1 161.7 8.8 12.9 45.8 90 7.9 7.9 13.9 74.5 7.9 10.8 35.9 Bow River above Calgary 10 167.9 167.1 145.1 -13.2 167.0 123.1 -26.3 20 107.6 107.0 100.9 -5.7 107.0 88.8 -17.0 30 87.6 87.5 88.1 0.6 87.5 73.9 -15.6 40 71.2 71.2 80.2 12.7 71.2 67.8 -4.7 50 65.8 65.7 73.2 11.5 65.7 65.8 0.2 60 61.0 60.9 68.7 12.9 60.9 62.9 3.2 70 57.6 57.5 64.4 12.0 57.5 60.4 5.1 80 54.2 54.2 60.0 10.6 54.2 58.3 7.5 90 50.0 49.9 56.9 14.0 49.9 55.6 11.4 Elbow River below Glenmore Reservoir 10 17.3 17.3 16.0 -7.3 17.2 15.9 -7.9 20 10.3 10.3 11.3 10.1 10.3 9.3 -10.0 30 7.1 7.1 8.8 25.0 7.1 6.8 -4.0 40 5.1 5.1 7.5 46.1 5.1 5.3 3.7 50 4.0 4.0 6.0 52.7 4.0 4.0 1.9 60 2.9 2.9 4.4 51.6 2.9 3.2 8.8 70 2.4 2.4 3.0 22.9 2.4 2.6 9.7 80 2.0 2.0 2.6 31.0 2.0 2.2 13.9 Combining the Methods: Using the CanRCM4 precipitation frequency distributions to perturb WRF- PGW precipitation fields
The modified method is as follows, for each grid cell and each month
1. random numbers are generated using the log-normal distribution fitted to the non-zero precipitation data of WRF for that month,
2. the non-zero precipitation values of the CanRCM4 simulation are ranked and
3. the values of CanRCM4 are replaced with the generated random numbers according to their ranks. Blueprint for future climate change impacts on hydrology Change to extreme streamflow events using CanRCM4 uncertainty and WRF-PGW forcing data
Bow River at Banff Change to extreme streamflow events using CanRCM4 uncertainty and WRF-PGW forcing data
Bow River at Calgary How to drive hydraulic models of flood plains using these outputs Conclusions
• Coupling dynamically downscaled climate and weather models to a physically based hydrological model can provide credible current and future hydrological simulations • Include glaciers, mountains, reservoirs • Weather models produce suitable precipitation dynamics, but climate models quantify uncertainty – both are needed for hydrological risk management • Uncertainty from climate model projects can be reduced and quantified by combining future climate and weather models and reducing bias by using streamflow records • In the Bow River Basin under climate change, future spring peak flows will increase at Banff due to earlier snowmelt and rain-on-snow but decrease at Calgary due to decreased rain-on-snow contributions to flood events. • Overall streamflow volumes will increase, but deglaciation may reduce late summer flows in the Bow River • This study provides a robust blueprint for calculating future streamflow discharge probabilities that can be used for mapping future floodplains. Questions?
33 Thank You!
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