Summer Water Temperatures in Alluvial and Bedrock Channels of the Olympic Peninsula

Abstract

Abstract To better understand how stream geomorphology may affect water temperature, we recorded water temperatures along two channels, one with deep alluvium and the other composed of bedrock and shallow alluvium. Study channels were located in managed forestlands on the Olympic Peninsula. Water temperatures were recorded hourly at 75-m intervals along 1.6 and 1.4 km of the alluvial and bedrock channels, respectively, during the summers of 2003 and 2004. Seasonal maximum and minimum daily water temperatures (i.e., season-long means for individual temperature dataloggers) in the alluvial channel tended to vary less over the course of the summer than temperatures in the bedrock channel. In addition, the means of all the individual dataloggers' daily maximums for each stream (reach mean maximum) and, similarly, the daily minimums (reach mean minimum) varied less for the alluvial channel. Changes in temperature from the upstream to downstream were greater for the bedrock channel, but only at low flow.