Date of Award

Summer 8-18-2015

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Andrew Reeve

Second Committee Member

Sean Smith

Third Committee Member

Amanda Olsen

Abstract

Heat transport studies often focus on calculating an average direction and magnitude of groundwater flow within the streambed for long (3 days – 1 week) periods of time. Short-term changes in flow magnitude and/or direction within the streambed caused by near stream groundwater pumping and storms are not represented by these long term averaging methods. Temperature profiles collected in B Stream (Houlton, Maine) and the Stillwater River (Orono, Maine) were used to calibrate a one-dimensional heat transport model and quantify short-term hydraulic events in vertical groundwater velocity within streambeds. Temperature profiles were collected during the summer of 2014 with iButton (Maxim Integrated, San Jose, CA) temperature loggers from two locations within each streambed to assess the spatial variability of groundwater flow within the streambed. Velocity values were averaged over daily periods allowing us to analyze how groundwater flow within the streambed changed during short-term hydraulic events. Bedrock wells at the B Stream site and surficial wells at the Stillwater River site were pumped while streambed temperature profiles were being collected. Temperature profiles were also collected before, during, and after Hurricane Arthur. Average modeled velocities were -4.38 x 10-6 m/s and -5.01 x 10-6 m/s (standard deviations of 8.02 x 10-6 m/s and 1.34 x 10-5 m/s) for the south and north locations at the Stillwater River site and were -1.13 x 10-5 m/s and -1.93 x 10-5 m/s (standard deviations of 1.46 x 10-5 m/s and 2.03 x 10-5 m/s) for locations 1 and 2 at the B Stream site. Significant (p = 0.0004) differences between location 1 and location 2 at the B Stream site were recorded while there is no significant (p = 0.64) difference between the north and south locations at the Stillwater River site. Model results indicate periods of directional change of groundwater flow at both study sites associated with short-term hydraulic events. Shifts within the Stillwater River are coincident with groundwater pumping while shifts within B Stream are coincident with storm events. Flow within the Stillwater streambed shifts from downward to upward as groundwater wells are turned off at the Stillwater location. Flow within the B Stream streambed shift from downward, to upward, then back to downward. Calculating average velocity over 24 hour time periods allowed for the detection of these changes in the direction of groundwater flow within the streambed.

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