Wetter, warmer, and more extreme weather is expected in the coming years, according to regional planners — and while there might be more moisture falling from the sky in the future, when and how it arrives is shifting.
The Capital Regional District’s (CRD) regional water supply commission heard from staff Wednesday, April 19, in a now-biennial report on the expected impact of climate change on the region’s water supplies. The report also examined how the changing climate will affect the way water is delivered between now and 2050 — emphasizing that current modelling for the CRD projects a slight net increase in total annual precipitation, but with summer drought conditions occurring more frequently, and for longer periods.
Annette Constabel, the CRD’s senior watershed protection manager, said the report’s outlook was similar to one presented in 2021, but included updates and new figures.
“Overall, it’s a good news story,” said Constabel, “in terms of the fitness of the current regional water supply system and meeting the demands of today.”
There was also good reason for optimism, said Constabel, in that water systems within the CRD could likely meet future demands, even under the current climate change scenarios. The climate models forecast an increase in fall, winter and spring rainfall, and a decrease in summers — a projected five per cent increase in total annual precipitation. That’s despite hotter summers — and fewer days with freezing temperatures in the winter — that will be evident in the general warming trend, according to the report.
But the big changes seem to be in how that precipitation will occur. Major rainfall events in the fall and winter will be more intense, longer in duration and more frequent, according to the report — with less frequent winter snowfall over time, but with more frequent heavy snowfalls and “rain on snow events” in the short term.
“There’s expected to be a greater variability in weather,” said Constabel, “meaning we could have much drier than usual years and much wetter than usual years — and for multiple years.”
Constabel presented data showing the impact of extremely dry springs on tree mortality — more significant, notably, than the heat dome event of June 2021. A dry spring followed the next year by a wet one allows forests a chance to recover, according to staff — but more than one in a row could have deleterious effects on watersheds, leading to downstream issues like increased turbidity and higher costs to produce potable water.
“We’re using the 2017 climate change projections from our local Pacific Climate Impacts Consortium office,” said Constabel, “which averages 12 global climate models, and then adjusted those results to our region.”
Those projections are being updated in late 2023, added Constabel, at which time a clearer picture should emerge on water supply impacts.