Black, Jenelle. 2001. Summer temperatures in small stream sources on managed Olympic Peninsula timberlands. M.S.
Read the full thesis here (12MB pdf)
In general, very little information exists on headwater streams and even less exists on the emergence areas of these streams. Given the large number of stream miles comprised of small headwater streams (Type 4 and 5 in the Washington State stream typing system) information is needed on the ecological processes that affect these streams. This study provides some of the first information collected in Washington on water temperature in these streams and in particular, water temperature at the point of emergence from the hillslope. Six sites at various elevations on the West side of the Olympic Peninsula were studied.
The study had 3 main objectives. The first was to compare water temperatures at point emergence areas (springs) and dispersed emergence zones (marshes and seeps) of headwater streams. The second was to investigate how source temperatures were affected by timber harvest and adjacent shade. The third was to compare temperatures measured in the field with current and proposed stream temperature regulations. Prior to data analysis it was decided that an investigation of various methods of collapsing continuous water temperature data would also be useful.
Temperature summary statistics can be grouped by the type of information about the temperature regime that they describe. Various metrics describe average, maximum, and minimum temperatures. There are also metrics that describe variability of the temperature regime and the magnitude/duration of various temperature categories. Within each of these 5 groupings, the various summary statistics tend to be highly correlated. For characterizing the complete temperature regime, inclusion of a statistic from each group is more important than which statistic is chosen from each group.
The hypothesis that the water temperatures of dispersed (marsh) sources of emergence would be warmer and more variable than point sources (springs) was supported. The hypothesis that source temperature of all sources would differ based on harvest status and shade level was not supported. The hypothesis that marsh temperatures would be more sensitive to harvest status was supported. Marsh temperatures were significantly warmer in areas that had been harvested. Spring temperatures were not significantly different between harvested and unharvested units.
Unlike findings from some other studies on stream temperatures, there was only a weak relationship between marsh temperature and mean or maximum air temperature and no relationship between spring temperature and air temperature.
A majority of the streams and stream sources in this study did not meet current or proposed temperature standards for mean weekly maximum temperature. This was true for streams in harvested and unharvested units, alike. No streams or sources exceeded 20C, but marshes temperatures regularly exceeded 16C.
This study looked at a very small number of stream sources and streams. A larger, more diverse data set may result in different findings. Extrapolation of these results is risky beyond the West-side of the Olympic Peninsula.