Graduate Thesis Or Dissertation
 

Processes that influence the downstream propagation of heat in streams below clearcut harvest units : Hinkle Creek paired watershed study

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/sn00b0897

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  • 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 Hinkle Creek watershed is located in the foothills of the Cascade Mountains about 30 kilometers northeast of Roseburg, Oregon, is privately owned, and supports a 60-year old, harvest-regenerated, Douglas-fir forest. The study watershed contains four treatment and two control sub-watersheds within the larger treatment and control watersheds, respectively. The first harvest entry, which took place during the winter 2005–2006, consisted of five clearcut harvest units located adjacent to perennial, non-fish-bearing streams. One year each of calibration and post-harvest data are analyzed. 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. A multiple linear regression model was used to compare the 2005 data with the 2006 data for each stream. Stream temperature data from Myers Creek (temperature probe C04) was the control. The model for this analysis was: yt = μ +α + βx + ε where yt is the temperature of the stream on a day t, μ is the overall mean value of y, αi is the effect of year, xt is the corresponding temperature of the control stream on a day t, β is the coefficient estimated by regression, and εt is the error term. This method is an analysis of variance of values that are adjusted for regression with an independent variable, in this case the maximum daily temperatures of the control stream. 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. Stream velocities calculated with OTIS ranged from 0.24 to 0.40 m/sec for the four streams. Dispersions ranged from 0.18 and 0.84 m2/sec. The estimated crosssectional area of the ‘immobile’ zones of water storage divided by the stream cross-sectional area, As/A or the storage ratio, varied from near zero to 7.2. The residence times of water in hyporheic storage ranged from 2.3 hrs to 32 hrs. Water stored in a shaded reach of stream, in pools, and in hyporheic zones provides a volume of water that can be exchanged with the water in the active stream channel. This provides for physical mixing with cooler water and heat transfer to the stream bed. 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. The air temperature was lower than stream temperature during four of those nights and the stream cooled due to a net loss of longwave radiation and evaporative cooling.
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