Water Stewardship Information Sources

Citation Jost, G and Weber, F. 2012. Hydrologic Impacts of Climate Change; Integrated Resource Plan Appendix 2C. BC Hydro
Organization BC Hydro
URL https://www.bchydro.com/content/dam/BCHydro/customer-portal/documents/corporate/regulatory-planning-documents/integrated-resource-plans/current-plan/0200c-nov-2013-irp-appx-2c.pdf
Abstract/Description or Keywords This document provides an introduction to the science of climate change and its impact on the
hydrology in British Columbia, and summarizes the implications of historical and future climate change on
the water cycle and water availability in watersheds managed by BC Hydro. This document uses the IPCC
definition of climate change, which is "a change in the state of the climate that can be identified (e.g.,
using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for
an extended period, typically decades or longer. It refers to any change in climate over time, whether due
to natural variability or as a result of human activity."
As part of BC Hydro's climate change adaptation strategy, BC Hydro has been working with some of
the world's leading scientists in climatology, glaciology, and hydrology to determine how climate change
has affected the water supply and what we can expect in the future. BC Hydro has formed partnerships
with the Pacific Climate Impacts Consortium (PCIC) and the Western Canadian Cryospheric Network
(WdN). In addition, BC Hydro has conducted internal studies to investigate historic impacts of climate
change on inflows.
When working with climate change scenarios it is important to realize that the goal of working with
scenarios is not to predict the future, but to better understand uncertainties in order to reach decisions
that are robust under a wide range of possible futures. The hydrologic climate change impact studies that
were commissioned by BC Hydro included a comprehensive assessment of uncertainties in predictions for
the 2050s that considered uncertainties in general circulation modeling, hydrologic modeling, and
uncertainties in possible emission trajectories. Despite substantial uncertainty in the magnitude of
projected changes, there is a general consensus of the direction of climate change:
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• Historical trends in annual reservoir inflows are small and not significant. There is some evidence
for a modest historical increase in annual inflows into BC Hydro's reservoirs.
• There is evidence for historical changes in the seasonality of inflows. Fall and winter inflows have
shown an increase in almost all regions; there is weaker evidence for a possible modest decline
in late-summer flows for those basins driven primarily by melt of glacial ice and/or seasonal
snowpack.
• For the period of inflow records (35 to 47 years, depending on the reservoir), the severity of
year-to-year fluctuations in annual reservoir inflow volumes has not changed.
• Projected warming in the 21st century shows a continuation of patterns similar to those of
recent decades.
• All emission scenarios project higher temperatures in all seasons in all areas of British Columbia
during the 21st century that will very likely be larger than those observed during the 20th
century. Precipitation projections suggest likely increases in winter, spring, and fall for all study areas
under all scenarios.
• A modest increase in annual water availability is likely for BC Hydro's hydroelectric system.
• Annual discharge in most Upper Columbia watersheds is projected to likely increase.
• In the Columbia and Kootenay regions, late fall and winter flows will increase slightly; the onset
of the snowmelt freshet will be earlier; spring a.nd early-summer flows will be substantially
higher; earlier peak flows and higher monthly peak flows can be expected; and late-summer and
early-fall flows will be substantially lower.
• Annual discharge is projected to increase in the Peace region, where late-fall and winter flows
will increase slightly; the snowmelt freshet will begin earlier due to higher spring temperatures;
and summer flows will be lower.
• Snow processes on the South Coast will become less important to the hydrology of tlie
watersheds; fall and winter flows will increase, with a larger fraction of precipitation falling as
rain; and spring and summer flows will decrease.
• The Campbell River area will see negligible changes to annual discharges.
The hydrological impact studies constitute the first step in BC Hydro's climate change adaption
strategy: identify current and future climate changes relevant to the system. Next steps are to assess the
vulnerabilities and risks to climate change across the BC Hydro system and then to develop an adaptation
strategy using risk-based prioritization schemes. The BC Hydro Adaptation Working Group will determine
where there may be vulnerabilities to climate change, and then specific hydrologic scenarios will be input
into existing planning models that simulate the current and future operation of the Generation system to
assess whether the operation of the system might need to be adapted in the future.
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