The Trask Watershed Study is a multi-disciplinary, long-term research project in the Oregon Coast Range that is designed to examine the effects of current forest management practices on aquatic ecosystems. Extensive physical (e.g., water quantity and quality, channel morphology) and biological data (e.g., primary productivity, macro-invertebrate communities, amphibian movement and fish populations and behavior) has been collected in both the small and large watersheds since 2006 and will continue until 2016. One of these key parameters we have been collecting at multiple scales is stream temperature.
Understanding the variability in stream temperature patterns and processes prior to harvest in both small non-fish headwater streams and downstream in larger fish-bearing basins allows us to anticipate potential responses to harvest and subsequent potential changes in biota. Using the pre-harvest stream temperature data we examine variability in maximum and minimum temperatures across the 15 small headwater streams. We also examine how well both small treatment streams and the larger downstream basins correlate to un-harvested reference streams to determine the best match to compare post-harvest response. Finally we examine how stream temperature patterns vary longitudinally in the downstream direction through time.

This research investigates the direct and downstream impacts of clearcut harvest units on stream temperature as a part of the Hinkle Creek Paired Watershed Study. The experimental design for the study was a Before-After-Control-Impact (BACI) design. Maximum daily stream temperatures (MDST) were analyzed for the four treatment streams for one year before and one year after harvest. The impact of timber harvest on MDST is small when compared to the spatial (between-stream) variation in MDST and this impact decreased downstream. At 300 meters, nominally, downstream of the harvest units the impact of timber harvest on MDST was not statistically significant for two streams and only moderately statistically significant for the other two streams. Stream velocity, discharge, and groundwater advection in the streams downstream of the harvest units were quantified using dye tracer dilution techniques. The One-dimensional Transport with Inflow and Storage (OTIS) model was used to quantify longitudinal dispersions, transient storage volumes, storage transfer rates, and hyporheic residence times in four 75 meter reaches in each of the four treatment streams. Latent heat, Sensible heat, Longwave Radiant heat and Photosynthetically Active Radiation (PAR) were calculated for August 7-17, 2006 at the center of the 300 meter study reach in Russell Creek.

Suspended sediment and in situ turbidity data from two western Oregon streams, Oak Creek and South Fork Hinkle Creek, were used to estimate annual sediment loads for the 2006 water year (October 1, 2005 to September 30, 2006). Water samples and in situ turbidity observations were taken following the Turbidity Threshold Sampling (TTS) protocol. The annual hydrographs for Oak Creek and South Fork Hinkle Creek were divided into storms which resulted in storm-specific relationships between in situ turbidity and Suspended Sediment Concentration (SSC). In the relationship between SSC and in situ turbidity, especially for Oak Creek, there are counterintuitive value which had to be vetted out with values of laboratory turbidity, hydrograph characteristics, and hysteresis loops. Observations of in situ turbidity considered erroneous were adjusted manually with the TTS-adjuster program. The objectives of this study were to determine the efficacy of an automated turbidity adjustment program compared with a manual turbidity adjuster, and to determine the efficacy of two in situ turbidity and SSC relationships to predict annual sediment loads. Relationships between SSC and in situ turbidity were made to estimate annual sediment load for Oak and South Fork Hinkle Creeks. The SSC vs. in situ turbidity relationships were made for storm-specific time periods and for the whole water year.

Few studies have examined both long-term and fine-scale spatial variations in water quality of small streams in the Pacific Northwest. As such, a case study was conducted to determine if current physical and chemical properties of water in three streams located in the Oregon Coast Range differed from historically measured conditions, taking differences in past management regimes into account. In addition, this research provides an assessment of spatial and temporal variability in nitrogen (N) concentrations and summer stream temperatures within each catchment. In this revisit to the Alsea Watersheds, measurements were conducted continuously (discharge, turbidity), intermittently (suspended sediments), and at regular intervals (nitrate-N) for one year between October 2005 and September 2006. Summertime stream temperature was also measured every half-hour from mid-June to mid-September. Comparisons of recent data with historic data show no detectable changes over time for streamflow characteristics (annual runoff volume, peak flow discharges, and number of low-flow days), annual sediment yield, or summer maximum stream temperatures. Synoptically measured stream temperatures were variable along each stream’s longitudinal profile. The ability to meet Oregon’s water quality standard for temperature was dependent on measurement location and method of analysis.