Date of Award:

12-2010

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Wayne A. Wurtsbaugh

Committee

Wayne A. Wurtsbaugh

Committee

Michelle A. Baker

Committee

Michael N. Gooseff

Abstract

Limnologists and stream ecologists acknowledge the fundamental importance of temperature for regulating many ecological, biological, chemical, and physical processes. I investigated how water temperatures were affected by hydrologic linkages between streams and lakes at various positions along surface water networks throughout several headwater basins in the Sawtooth and White Cloud Mountains of Idaho (USA). Temperatures of streams and lakes were measured for up to 27 months in seven 6 – 41 km2 watersheds, with a range of lake influence. When they were ice-free, warming in lakes resulted in dramatically warmer temperatures at lake outflows compared to inflow streams (midsummer average 6.4°C warming, but as much as 12.5°C). Temperatures cooled as water traveled downstream from lakes, as rapidly as 9°C km-1. Longitudinal stream cooling was usually not strong enough, however, to reduce temperatures to baseline conditions. In early spring, lakes had the opposite effect on streams, as they released water from beneath the ice at near 0°C. Early spring stream water warmed as it flowed downstream from lakes, influenced by additional groundwater inflows. In addition to lakes, other watershed characteristics influenced temperatures, though effects differed seasonally. Multiple regression analyses indicated that lake size, distance from nearest upstream lake, and stream shading were most important in explaining stream temperatures, but the relative importance of each variable changed seasonally.

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66dcd39eeee817db24e3f78f583be76f

Comments

This work made publicly available electronically on January 19, 2011.

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