Hydrology & Water Quality

Local and Downstream Effects of Contemporary Forest Harvesting on Streamflow and Sediment Yield
Zégre, N. P.

This dissertation is a collection of three manuscripts that serve to fill the knowledge gaps and advance methods of detecting the effects of contemporary forest harvesting in experimental catchment studies. The objective of this research was to develop change detection models using time-series records to detect and quantify the effects of forest harvesting on streamflow and sediment yield. To accomplish this, it was necessary to characterize streamflow and sediment processes at a temporal scale capable of describing daily, monthly, and seasonal dynamics following forest harvesting; increase sample sizes used to construct regression-based change detection models; and develop alternative methods to the paired-catchment approach in order to discern changes in streamflow and sediment using highly variable time-series data. The paired-catchment approach was used to detect and quantify relative changes in streamflow and sediment yield in 5 harvested catchments. The ability to detect statistically significant changes at certain time-steps was a function of accounting for all sources of variability in change detection models. In this study, we aimed to develop robust change detection models using time-series data to increase sample size and decrease false/missed detections of true treatment effects.

DISCIPLINE: Hydrology & Water Quality    STUDY: Alsea, Hinkle Creek, Trask    TYPE: Theses    TAGS: forest harvesting, contemporary harvesting practices, detection models, paired-catchment, sediment yield
On the Estimation and Application of Spatial and Temporal Autocorrelation in Headwater Streams
Som, N.

This collection of three manuscripts serves to improve methods for collecting, interpreting, and utilizing autocorrelated data from headwater stream networks. Two chapters of this work relied on a unique and comprehensive set of data which constitutes a complete census of habitat unit fish counts from 40 randomly selected headwater basins in western Oregon. The first objective of this work was to evaluate how different sampling designs captured spatial autocorrelation, given the samples were drawn from a population of spatially autocorrelated observations. The second objective was to investigate spatial autocorrelation model range parameters as measures of patch sizes. The third objective was to refine the analysis of temporally autocorrelated hydrology data from paired watershed studies. These  are used to evaluate forest harvesting effects on stream biota and hydrology (i.e. fish, amphibians, insects, stream flow, and sediment yield).

DISCIPLINE: Hydrology & Water Quality    STUDY: Alsea, Hinkle Creek, Trask    TYPE: Theses    TAGS: autocorrelated data, headwater stream networks, Spatial autocorrelation, patch size, paired watershed studies
Exploring the Differences between Lagrangian and Eulerian Reference Frames for Stream Temperature Data
Egan, F.

Stream temperature research relies on reference frames in which to project data. An important decision in the project design is which frame of reference to use. This aspect of research planning is not always given the consideration of thought that would lead to the best decision. In this thesis, two frames of references (Eulerian and Lagrangian) are compared in order to garner a better understanding of whether the choice of one reference frame over the other leads to a difference in the interpretation of the stream temperature data. The Eulerian and Lagrangian reference frames were compared through a series of graphs in which the data was projected on both reference frames. In two dimensions of space and temperature, the interpretation between the Eulerian and Lagrangian reference frames are fairly similar. When the third dimension of time was graphed alongside temperature and space, the interpretations of the data differed between reference frames. All three dimensions should be considered when choosing a reference frame for research projects. The appropriate reference frame to use depends on the statements that need to be made about the data at the conclusion of the study.

DISCIPLINE: Hydrology & Water Quality    STUDY: Hinkle Creek    TYPE: Theses    TAGS: Reference frame, Eulerian, Lagrangian, Hydrology, Stream temperature
Effect of contemporary forest harvesting practices on headwater stream temperatures: Initial response of the Hinkle Creek catchment, Pacific Northwest
Kibler Kelly M., Skaugset, Arne, Ganio, Lisa M., Huso, Manuela M.

We investigated the effect of contemporary forest harvesting practices on warm-season thermal regimes of headwater streams using a Before-After-Control-Intervention (BACI) design within a nested, paired watershed study. We applied harvesting treatments to four headwater tributaries of Hinkle Creek, designed in accordance with the Oregon Forest Practices Act. Therefore, fixed-width buffer strips containing overstory merchantable trees were not left adjacent to the four non-fish-bearing streams. The summer following harvesting, we observed a variable temperature response across the four harvested streams. Mean maximum daily stream temperatures ranged from 1.5 C cooler to 1.0 C warmer relative to pre-harvest years. We also observed significantly lower minimum and mean daily stream temperatures, and recorded particularly low temperatures in treatment streams on days that minimum stream temperatures in reference streams were high. At the watershed scale, we did not observe cumulative stream temperature effects related to harvesting 14% of the watershed area in multiple, spatially-distributed harvest units across four headwater catchments. At the watershed outlet, we observed no change to maximum, mean, or minimum daily stream temperatures. We attribute the lack of consistent temperature increases in headwater streams to shading provided by a layer of logging slash that deposited over the streams during harvesting, and to increased summer baseflows.

DISCIPLINE: Hydrology & Water Quality    STUDY: Hinkle Creek    TYPE: Journal Articles    TAGS: Stream temperature, Forest management, Canopy closure, Impact assessment, Headwater streams, Cumulative effects, Hinkle, Oregon, Paired Watershed, Forest Hydrology


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