Citation | Quilty, EJ, Hudson, PMB, Farahmand, T. 2004. Living on the edge: climate change and salmon in Lang Creek, British Columbia. Prepared for BC Ministry of Environment. |
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Organization | Ministry of Environment |
URL | http://www.env.gov.bc.ca/epd/regions/lower_mainland/special_studies/lang_creek/lang_creek.pdf |
Abstract/Description or Keywords | Haslam Lake and Lang Creek, located just west of Powell River on the Sunshine Coast, are within a multiple-use community watershed that currently provides drinking water for approximately 20,000 people of Powell River and Brew Bay. The system is also a substantial fisheries resource, with 2003 returns of approximately 1800 Coho, 1800 Chinook, 1000 Pink, 10,000 Chum, 500 Steelhead, and some Sockeye. Water temperatures in this system are very warm during summer and are known to have exceeded 30o C in the marshy headwaters of Lang Creek, though they cool downstream through contributions of cooler tributaries and groundwater, and from evaporation and riparian processes. The British Columbia Ministry of Water, Land and Air Protection (MWLAP) hired Aquatic Informatics Inc. to complete an investigative study on the watershed. The objectives of this study were to: 1. Evaluate recent impacts of warm stream temperatures to salmonids in Lang Creek; 2. Estimate the impacts of climate change on Lang Creek salmonid populations; 3. Forecast the impacts of climate warming and climatic cycles on future stream temperatures in Lang Creek; and 4. Develop water temperature objectives for the protection of drinking water and aquatic life. Within the observation period (1998-2004), summer water temperatures in upper Lang Creek routinely exceeded 24o C, and occasionally exceeded 26o C. In the mid and lower reaches, water temperature tended to be approximately 2 - 4o C cooler, depending on the contributions from the cooler tributaries. Exposure (magnitude and duration) based risk assessment was conducted to evaluate the effects of high stream temperatures in Lang Creek during the observation period. Temperatures in upper Lang Creek were warm enough to potentially cause mortalities as high as 52% - 97%, depending on the salmon species. In mid and lower Lang Creek, temperatures were at least 2o C and 4o C below lethal thresholds respectively, even during the warmest year. This can be attributed to the downstream cooling processes. Overall, although temperatures exceeded lethal thresholds in upper Lang Creek and approached lethal thresholds in mid Lang Creek, high water temperatures likely did not pose acute risk to salmon and trout species in the system during the observation period. This is because the fish are known to move to cooler refuge habitat in the tributaries and deep water of the lakes. Habitat exclusion and isolation, however, are likely occurring during summer as fish avoid warm temperatures in upper and mid Lang Creek and are inhibited from moving through these reaches to other suitable habitat. Even when temperatures in Lang Creek are below lethal thresholds, the temperatures are well above those considered optimal for rearing and would cause chronic impacts such as reduced growth and resistance to disease and stress. The fish in the watershed are therefore highly vulnerable to any habitat or water quality deterioration in the lakes and tributaries, to reduced summer flows in the tributaries, and to further warming in the mainstem. As a background to how climate has been changing in the Powell River area, the impacts of global warming over the last 80 years were estimated. Our results suggest atmospheric warming of approximately 0.8o C in winter and 0.3o C in spring. Summer and fall appear not to have been affected. Precipitation has also increased, with highest increases during winter (~1.2 mm/day) and spring (~0.8 mm/day), and modest increases during summer and fall (~0.5 mm/day). |
Information Type | report |
Regional Watershed | Howe Sound & Sunshine Coast |
Sub-watershed if known | Lang Creek |
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Project status | complete |
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