This study investigated carbon dynamics in the hyporheic zone of a steep, forested catchment in the Cascade Mountains of western Oregon, USA. Water samples were collected monthly from a headwater stream and well network during baseflow conditions from July to December 2013 and again in March 2014. We also sampled...
Stream discharge is a key water balance component and important factor in global change evaluations. Nevertheless, the mechanisms for streamflow generation are poorly understood. Near- stream surface saturation during precipitation events is one of the most iconic, visible indicators of rapid runoff production in upland humid catchments around the world....
The conventional advection-dispersion equation cannot adequately describe all processes driving
solute transport in heterogeneous systems. This dissertation focuses on the individual influences
of both chemical (Chapter 2) and physical processes (Chapters 3 and 4) which affect
solute transport. In Chapter 2 we analyzed uranium transport in natural sediment using the...
Streams and rivers play a critical role in global carbon (C) cycling by processing, storing, and transporting C. Headwater streams which make up more than 95% of the length of streams and rivers worldwide have disproportionate influence on fluvial C dynamics. The hyporheic zone (HZ) of headwater streams is a...
Recent advances in imaging technology and numerical modeling have greatly enhanced pore-scale investigations of multiphase flow and transport in porous media. It is now feasible to obtain high resolution 3-dimensional pore-scale data, and numerical methods such as the lattice-
Boltzmann (LB) technique have been developed specifically for simulating such phenomena....
Temperature is a key factor for salmonid health and is an important restoration metric on the Middle Fork of the John Day River in northeast Oregon. In the past century, dredge mining, deforestation, and overgrazing have degraded stream habitat and resulted in greater daytime stream temperatures in the region. Recent...
This dissertation concentrates on the controlling factors on the instability of the Laurentide Ice Sheet (LIS) and their effects on abrupt climate change. Northern Hemisphere climate fluctuated abruptly during the last deglaciation possibly related to variability in Atlantic meridional overturning circulation (AMOC) and reduced aerial extent of the LIS. Reductions...
The basaltic landscapes of the Oregon High Cascades form a natural laboratory for examining how geologic setting and history influence groundwater flowpaths, streamflow sensitivity to climate, and landscape evolution. In the High Cascades, highly permeable young basaltic lavas form extensive aquifers. These aquifers are the dominant sources of summer streamflow...
The City of Woodburn, Oregon's Wastewater Treatment Plant (WWTP) has been investigating several natural alternatives for improving effluent quality. Based on its current National Pollution Discharge Elimination System (NPDES) permit, the WWTP will require additional reduction of temperature and ammonia levels in the summer, especially in the critical month of...
This thesis consists of three subsequent parts addressing the applications of stochastic
processes to the analysis and solutions of parabolic equations with discontinuous coefficients
that are of mathematical interest.
The first two parts consist of three manuscripts, in which we analyze solutions
of Fickian convection dispersion equations with discontinuous coefficients...