Water Stewardship Information Sources

Citation Little, P. 2012. Theodosia Watershed: Climate Change Impacts and Adaptation Plan. Prepared for Theodosia Stewardship Roundtable.
Organization Living Rivers - Georgia Basin/Vancouver Island
URL http://www.fraserbasin.bc.ca/_Library/CCAQ_BCRAC/bcrac_theodosia_watershed_plan_2d.pdf
Abstract/Description or Keywords The Theodosia watershed is a 140 km2 coastal basin situated approximately 30 km north of
Powell River. Land and water use in the watershed includes forestry and diversion of water for
hydroelectricity. Well over half of the basin area has been harvested at least once and the
diversion extracts over 60% of the water from the upper Theodosia River. The river supports
substantial populations of Chum and Coho salmon, which have severely declined since the early
1950s, and provides habitat for several other salmonids.
Increased CO2 concentration in the earth’s atmosphere is resulting in several changes to the
climate and hydrology of the Theodosia watershed. Summers are projected to become dryer and
hotter with more frequent heat waves and increased year-to-year variability compared to
historical levels. Winters will likely be warmer and wetter. Large and frequent winter rainstorms
and a large decrease in snowfall at all elevations in the watershed should be expected.
Changes in climate will result in changes in the hydrology of the Theodosia River. Reduced
snowpack will result in a shift in timing of streamflow to earlier and diminished spring peak
flows. By the middle of the 21st century, it is likely that very little snowpack will be left to
contribute to spring streamflow. Furthermore, reduced snowfall, decreased summer precipitation,
and increased temperatures will likely result in lower summer/fall stream flow and more extreme
low flow periods. The river will also likely experience increases in the frequency and magnitude
of fall and winter flood events. Increased stream temperature at all times of year should also be
Climate change will impact stream habitat and salmonids in several ways. The greatest
impacts will likely come from increased frequency and magnitude of winter floods that will
increase scouring and burial of both Coho and Chum salmon eggs. Lower summer and early fall
streamflow will also be detrimental to fish populations, as will possible complex interactions due
to mismatched timing of predator/prey interactions or mismatched life history stages with the
hydrologic regime. Chum salmon may be able to better adapt to the future climate regime than
Coho although yet unknown complex interactions add uncertainty to this statement. Impacts to
forest resources may be less severe than impacts to fisheries, with the most common impact being
lower growth rates. However, it is possible that large-scale disturbances due to fire and/or
insect/disease outbreaks may have severe consequences to the forests of the watershed. The
likelihood of such impacts is very difficult to predict.
The final chapter of this document outlines several adaptation strategies that may serve to
increase the resilience of ecosystems in the watershed. The Theodosia Stewardship Roundtable
(TSR) must work to enhance the lines of communication between stakeholders and to develop
shared decision making protocols in the face of climate change. A water use plan for the Olsen
Lake diversion should be created and future infrastructure should reflect this plan. It is
recommended that water extraction during the summer is decreased to mitigate effects of
drought, while water use during the winter is managed to mitigate impacts of peak flows in the
lower watershed. Forest companies and the BC Ministry of Forests, Lands and Natural Resource
Operations should work with the TSR to develop a coordinated watershed-scale sustainable
harvesting plan that details targeted harvest rates, new protocols for culvert sizing, and plans for
restoration and conservation of floodplain forests. Flood risk, landslide risk and risk of storm
surge due to sea level rise will increase in the lower floodplain area; thus, future settlement plans
will require professional surveying to avoid locating buildings in high-risk areas.
Information Type report
Regional Watershed Howe Sound & Sunshine Coast
Sub-watershed if known Theodosia
Aquifer #
Project status
Contact Name
Contact Email