RESEARCH INTERESTS
I am broadly interested in exploring the hydrogeomorphic template of catchment ecosystems. Specifically, I focus on hydrologic and ecological responses to climate and land use change, and the hydrologic controls on complex aquatic and terrestrial ecosystem processes. Therefore, I am interested in:
* Groundwater-Surface Water Exchange
* Aquatic Ecology and Biogeochemistry
* Nutrient & Energy Retention in Stream Ecosystems
* Floodplain-River Interactions
* Streams, wetlands, and intertidal zones as dynamic transport systems
I approach these interests in terms of how catchment dynamics and surface-ground water interactions affect aquatic ecosystems through solute generation, fate, and transport. My methods involve innovative characterization techniques (e.g., tracers, isotopes, and geophysics) and deterministic modeling which couple hydraulic and ecosystem processes (e.g., reactive nutrient transport).
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ACTIVE RESEARCH
1. FLOW REGIME CONTROLS ON RIVER NITROGEN AND CARBON EXPORT UNDER PAST, PRESENT, AND FUTURE CLIMATE CONDITIONS
The objective of this project is to elucidate how river flow regimes control catchment nitrogen and dissolved organic carbon exports. To achieve this, we will relate hydrologic transport variability to nitrogen and carbon export of major river networks of varying scales under past, present, and predicted future climate regimes. This research strives to reevaluate the ecological theory of nutrient processing in rivers. Furthermore, this project will help develop published ecological-flow relationships at multiple scales that will inform water-quality conservation measures, which in turn conserve freshwater and marine biodiversity, including culturally and economically valued fish, invertebrate, and plant species.
Collaborators:
James Saiers, PhD (Yale University)
Peter Raymond, PhD (Yale University)
2. ROLE OF HYPORHEIC PROCESSES ON NITROGEN CYCLING IN STREAMS
Key objectives of this research are to collect and utilize independent (i.e., geophysical, hydraulic, isotope, and biophysical) characterizations of dominant stream types to: 1. develop integrated methods for overcoming current limitations in groundwater-surface water research and, 2. develop a groundwater-surface water exchange model for water and nitrogen to elucidate hyporheic controls on watershed nitrogen yields. Subsequently, the methods and resulting model can be used to address crucial questions, such as: 1. What are the dominant physical and biophysical controls of the hyporheic zone on nitrogen dynamics?, 2. Can we develop scaling relationships by linking physical and biological controls?, 3. What stream types function as nitrogen sources versus sinks?, 4. Which stream types are most effective at regulating downstream nitrogen export?, and 5. How can we incorporate the self-purification mechanisms of the hyporheic zone in river restoration and management efforts?
Collaborators:
Roy Haggerty, PhD (Oregon State University)
Steve Wondzell, PhD (Oregon State University)
Michelle A. Baker, PhD (Utah State University)
Vrushali Bokil, PhD (Oregon State University)
Alba Argerich, PhD (Oregon State & Universitat de Barcelona, Spain)
Nigel Crook, PhD (CUASHI_HMF, Stanford Univ.)
David Robinson, PhD (CUASHI_HMF, Stanford Univ.)
Rosemary Knight, PhD (CUASHI_HMF, Stanford Univ.)
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3. IDENTIFYING GROUNDWATER-SURFACE WATER CONNECTIVITY IN A STRONGLY GAINING STREAM ENVIRONMENT, CANTERBURY PLAINS, NEW ZEALAND
In general, lowland strongly-gaining streams are considered to be discharge points for groundwater aquifers. However, there are many mechanisms that create bi-directional ground water – surface water exchange (e.g., bed topographic and hydraulic conductivity variations). With this in mind, low-land gaining streams may be exhibit more complex bidirectional gw-sw exchange patterns than currently treated in conceptual models. We are using multiple empirical and modelling methods to evaluate the potential for bidirectional dynamics along strongly-gaining lowland streams in the highly heterogeneous alluvial depositional plains of Canterbury, New Zealand. Scale and "window of detection" for gw-sw exchange processes are very important. We are able to quantify gross gains and losses along discrete segments of a gaining stream by taking a nested observation and modelling approach.
Collaborators:
Mandy Meriano, PhD (University of Toronto)
MS Srinivasan, PhD (National Institute for Water & Atmospheric Research, Inc, New Zealand)
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4. LINKING GEOPHYSICS AND SMART TRACERS TO COMPLEX STREAM METABOLIC PROCESSES
In this work we seek to use novel electrical resistivity measurement techniques in conjunction with novel metabolically-sensitive hydrologic tracers to identify coupled physical and biological controls on stream and hyporheic metabolism. This work consists of two collaborating research teams - an electrical resistivity research group from Pennsylvania State and a stream ecohydrology group from Oregon State University. Together we are assessing time-lapse surface and subsurface (hyporheic) solute transport and metabolically active transient storage zones in the stream system. This work is being done in the H.J. Andrews Experimental Forest, LTER site, Oregon, USA.
Collaborators:
Adam Ward (Iowa State University)
Alba Argerich, PhD (Oregon State & Universitat de Barcelona, Spain)
Sherri Johnson, PhD (PNWRS, US Forest Service)
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5. EFFECTS OF WAVES ON SOLUTE TRANSPORT THROUGH EMERGENT VEGETATION
Understanding the interactions between near-shore hydrodynamics and vegetation in coastal areas is necessary to develop strategies for managing and protecting coastal ecosystems and built systems. However, there is little understanding of these interactions. Wave-vegetation interactions are difficult to study in natural settings because collecting and analyzing field data of wave attenuation and fluid flow characteristics in coastal vegetation is logistically and mechanistically complex (e.g., equipment fidelity, dynamic wind speeds and direction, tides, wave refraction and shoaling). Models of wave-plant interactions can be developed, but will be limited until experiments focused on the interactions between waves on real vegetation are completed. Therefore, we are conducting controlled waves and vegetation interaction experiments in a laboratory environment at prototype scale with live plants. These large-scale laboratory experiments are conducted in a Large Wave Flume (104m long, 3.6m wide, and 4.6m deep) at the O.H. Hinsdale Wave Research Laboratory (HWRL) at Oregon State University. Live plants (Schoenoplectus pungens or threesquare bulrush) are collected from the field (Tillamook, Oregon, USA). To our knowledge, this is the first test using live plants in a controlled, high energy wave environment.
Collaborators:
Dan Cox, PhD (Oregon State University & Hinsdale Wave Research Laboratory)
Dennis Albert, PhD (Oregon State University)
Heather Smith, PhD (Louisiana State University)
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COMPLETED RESEARCH
Complete list of published research is HERE.
Hydrogeophysics:
This collaborative work focused on the use of Ground Penetrating Radar and Electrical Resitivity Imaging to improve spatial and temporal characterizations of stream subsurface environments.
Solute Transport:
This collaborative work focused on improving our understanding of stream tracer experiments and their ability to differentiate between different sources of transient storage - surface (i.e., pools, eddies) and subsurface (i.e., hyporheic zone).
Climate Change Impacts on Arctic Streams:
This collaborative work was conducted as a component of the Arctic Hyporheic Project. The major objective of this project was to investigate the responses of arctic tundra stream hyporheic zone hydrology and biogeochemical cycling to predicted climate change.
Collaborators:
Michael N. Gooseff, PhD (Penn State University)
W. Breck Bowden, PhD (University of Vermont)
Troy Brosten, PhD (USGS, Boise State University)
James McNamara, PhD (Boise State Uninversity)
John Bradford, PhD (Boise State University)
Robert Payn, PhD (Montana State University)
Michelle A. Baker, PhD (Utah State University)
John (Jack) C. Schmidt, PhD (Utah State University)
