Event Title

Pervasive Lake Effects on Stream Temperatures

Presenter Information

Jessie Garrett

Location

Space Dynamics Laboratory

Event Website

http://water.usu.edu/

Start Date

3-25-2004 11:20 AM

End Date

3-25-2004 11:25 AM

Description

The presence and distribution of lakes may significantly affect temperatures throughout a watershed due to the solar heating of lakes’ large exposed water area. We placed thermistors along in 33 stream locations above and below lakes in the Sawtooth Mountains of central Idaho to view temperature changes at a landscape perspective. Lakes are common throughout these watersheds, with an average inter-lake distance of 2.8 km. Headwater streams unaffected by lakes were cold (5-6°C mean daily temperature in mid- to late summer). Even small lakes produced 3 to 6°C warming in streams below them. This warming persisted throughout the remainder of the network. Larger lakes (surface area > 8 ha) all produced mean daily outflow temperatures greater than 16°C, with as much as 11.5°C average warming from inflow to outflow. Outflow streams trended toward 8-10°C within 2 km below a lake, but even 5 to 7.5 km below the lakes, temperatures did not reset to initial conditions, as suggested by the Serial Discontinuity Concept (Ward and Stanford 1983). The biotic consequences of these higher outflow temperatures, both immediate and farther from the lake, are evident in fish growth rates (a change from 6 to 12°C increases trout size 370%, Elliot 1994), species-specific thermal tolerances, and community metabolic rates. In concert, these effects can alter aquatic assemblages and whole ecosystem function.

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Mar 25th, 11:20 AM Mar 25th, 11:25 AM

Pervasive Lake Effects on Stream Temperatures

Space Dynamics Laboratory

The presence and distribution of lakes may significantly affect temperatures throughout a watershed due to the solar heating of lakes’ large exposed water area. We placed thermistors along in 33 stream locations above and below lakes in the Sawtooth Mountains of central Idaho to view temperature changes at a landscape perspective. Lakes are common throughout these watersheds, with an average inter-lake distance of 2.8 km. Headwater streams unaffected by lakes were cold (5-6°C mean daily temperature in mid- to late summer). Even small lakes produced 3 to 6°C warming in streams below them. This warming persisted throughout the remainder of the network. Larger lakes (surface area > 8 ha) all produced mean daily outflow temperatures greater than 16°C, with as much as 11.5°C average warming from inflow to outflow. Outflow streams trended toward 8-10°C within 2 km below a lake, but even 5 to 7.5 km below the lakes, temperatures did not reset to initial conditions, as suggested by the Serial Discontinuity Concept (Ward and Stanford 1983). The biotic consequences of these higher outflow temperatures, both immediate and farther from the lake, are evident in fish growth rates (a change from 6 to 12°C increases trout size 370%, Elliot 1994), species-specific thermal tolerances, and community metabolic rates. In concert, these effects can alter aquatic assemblages and whole ecosystem function.

https://digitalcommons.usu.edu/runoff/2004/AllPosters/10