What determines river temperature in a changing watershed?

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Each river is shaped by the watershed that feeds it. The particular mountains, valleys, forests, rocks, and weather of a watershed interact to shape what a river looks and feels like for the fish that live there. This is true of water temperature, which affects every stage of fish life.

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Activities that shape the landscape –like forestry and development –change how water moves from the sky to the river mouth. Climate change is also affecting precipitation, snowpack, and air temperature, which all influence the river downstream.

 

The Nicola watershed, prone to summer droughts and spring floods, is under extra pressure from forestry, water use, and climate change. The Chinook salmon, coho salmon, and steelhead in the Nicola River are currently endangered. Water temperatures in summer regularly exceed 20°C, when juvenile salmon are rearing and adults are returning to spawn. Pine beetle infestation and associated forestry are also changing the landscape at large scales. A trend towards warmer, rainier winters may be increasing winter floods while reducing snowpack.

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In this watershed with many pressures, I am interested in how land and water management are interacting with weather and hydrology to determine patterns of river temperature over multiple years. I am also interested in how patterns in water temperature shape salmon habitat. To that end, I am monitoring water temperature at dozens of sites throughout the watershed. Together with information on land cover, water use, flow, and weather, this research will help us understand how temperatures in tributaries, reservoirs, and the mainstem coalesce into what fish are experiencing. I am also studying how weather extremes in summer and winter influence Chinook salmon while they are in freshwater. Our results should help inform planning and practice for water and land use in the Nicola.

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Questions? Don’t hesitate to contact me: luke_warkentin@sfu.ca.