British Columbia

B.C. has seen worse droughts than previously thought, tree rings reveal

Tree rings are letting University of Victoria researchers peer further into B.C.'s water history, and the results show more extreme droughts than previously thought.

Data on 350 years of B.C. droughts reveals extremes that were not recorded before, says researcher

By analyzing tree rings, researchers are able to peer further back into B.C.'s water history than the existing records. Shallower tree rings reveal years of more extreme summer drought, says researcher Bethany Coulthard. (Getty Images/EyeEm)

Residents on B.C.'s South Coast will likely have to endure worse droughts in the coming decades than previously thought according to a new study from the University of Victoria.

Researchers used tree ring data to reveal centuries of B.C.'s water history — much further back than the 50 or so years that humans have been keeping stream-flow records.

Looking at more than 350 years of tree ring data from B.C.'s South Coast, the study found 16 historical droughts that were worse than the benchmarks used today by water managers in the region, said Bethany Coulthard, paleoclimatologist and lead author of the study, published in the Journal of Hydrology.

She said B.C. should expect future droughts to reach the extremes of the past — and then some, due to added factors including human-caused climate change.

"Going into the future, we can expect that droughts of that severity are not only going to happen, but they're going to be made even worse by the additional pressure from land-use change and from climate change."

"We can reasonably anticipate that droughts worse than anything we've reconstructed in the past 350 years will be happening in the coming decades."

“We can reasonably anticipate that droughts worse than anything we’ve reconstructed in the past 350 years will be happening in the coming decades," says Bethany Coulthard a paleoclimatologist. (Getty Images/RooM RF)

Tree ring data back to 1658

The depth of the each tree ring — representing a year of growth — gives important information about the environment in that year, Coulthard said.

The smaller the tree rings, the more extreme the conditions, with snowpack levels and summer heat and dryness both affecting how severe a drought is.

Researchers used the rings to reconstruct water history in the area dating back to 1658.

Coulthard hopes B.C. authorities will consider this new data as they map out water-use strategies for the future and take a conservative approach.

"We need to know that even if we have high streamflow runoff years, they can be followed by very severe drought."

Coulthard warns that although at-risk species like salmon have survived droughts in the past, more severe droughts in the future may prove too much for some populations.

With files from Meera Bains

Authorities need to take a more conservative approach to water usage restrictions, says Coulthard. (Mario Anzuoni/Reuters)