Hyporheic Exchange Along the River Continuum
Steve Wondzell (Oregon State University, U.S. Forest Service)
Roy Haggerty (Oregon State University)
Fredrick Swanson (Oregon State University, U.S. Forest Service)
Overview: The River Continuum Concept provides a framework within which scientists are able to conceptualize changes in stream ecosystem processes from headwaters to oceans. We propose that along the same continuum, stream geomorphic characteristics change predictably, and that those changes also drive changes in hyporheic exchange and hyporheic zone extent. Previous hyporehic zone research has been confined to relatively short stream reaches (generally < 1 km). Within a larger view, one conceptual model that has been put forth for a "hyporehic continuum" proposes that alternating constrained and unconstrained reaches control hyporheic zone extent, "like beads on a string". Our project activities have been focused on the geomorphic template of streams, which drives hyporheic exchange, and its nature within a stream network.
Geomorphic Controls on Hyporheic Exchange:
We have characterized the controls on scaling of hyporheic exchange flow from the reach to the network, using data from geomorphology, stream tracer tests, and groundwater hydraulics. We have shown how hyporheic exchange flow is driven by the geomorphic expression of the stream, which we have quantified through detailed topographic surveys of more than 12 km of streams in the 64-km2 Lookout Creek Basin and through installation of piezometers networks in 3 reaches. We found that longitudinal stream water and bed surface profiles are critical drivers of hyporheic exchange in 2nd through 5th-order mountain streams.
Key results from this part of our work include:
part of the study provides a physical basis for making predictions
about the scaling of hyporheic zones in step-pool streams based on the
shape of the water surface profile and correlates this to basin area.
2nd-order stream in the H.J. Andrews Experimental Forest, photo by Mike Gooseff.
Stream Tracer Technique: We have developed and applied a new stream
tracer technique that measures the residence time distribution (RTD) in
the hyporheic zone of a stream. The method uses late-time
concentrations of RWT dye (or other tracers) measured with a field
fluorometer in real time at one or more downstream locations after a
release. Because the late-time concentrations are very sensitive to the
hyporheic RTD, the technique is able to quantify hyporheic transient
storage processes more precisely than conventional methods. Results
from more than 10 different stream reaches suggest that hyporheic
exchange RTDs display power-law behavior. Efforts to characterize the
mean hyporheic residence time in these streams will fail because the
underlying distribution of RTDs has either a very large or an infinite
variance. This implies the hyporheic zone has a very large range of
exchange timescales, with significant quantities of water and solutes
stored over all time-scales from short to long.
Hyporheic Exchange and Groundwater Flow Models: We have developed a series of calibrated groundwater flow models, in 2 and 3 dimensions, of 4 stream reaches to evaluate hyporheic exchange in these reaches. Tracer tests in these reaches were modeled and compared to existing data to verify model predictions. We have also used solute transport and groundwater flow models to generate residence time distributions, thereby connecting geomorphic data to stream tracer data for the first time. Groundwater models appear to be helpful in our understanding of hyporheic exchange, but preliminary results suggest that they are sensitive to parameters that are difficult to obtain, such as the thickness and bottom topography of alluvium-bedrock contact. The methodology also shows that there are some discrepancies between hyporheic volumes and residence times based on geomorphic stream surveys and those measured by stream tracer tests.
Network-Tracer Test: In the summer of 2003 we performed a network-scale RWT stream tracer experiment to investigate spatial scaling of hyporheic exchange charactersitics along the river continuum. This data are currently being analyzed.
Location: Our field sites are located in the H.J. Andrews Experimental Forest, which encompasses the Lookout Creek basin (5th-order).
R., S. M. Wondzell, and M. A. Johnson. 2002. Power-law
residence time distribution in the hyporheic zone of a 2nd-order
mountain stream. Geophysical Research Letters, 29:1640,
T. and S. M. Wondzell. 2003. Geomorphic
controls on hyporheic exchange flow in mountain streams. Water Resources Research
M. N., S. M. Wondzell, R. Haggerty, and J. K. Anderson. 2003. Comparing
transient storage modeling and residence time distribution (RTD)
analysis in geomorphically varied reaches in the Lookout Creek basin,
Oregon, USA. Advances in Water Resources, 26:925-937.
MN, JK Anderson, SM Wondzell, J LaNier, and
R Haggerty. 2006. A
modeling study of hyporheic exchange pattern and the sequence, size,
and spacing of stream bedforms in mountain stream networks, Oregon, USA.
Processes, 20(11): 2443-2457.
JK, SM Wondzell, MN Gooseff , and R
Haggerty. 2005. Patterns
in stream longitudinal profiles and implications for hyporheic exchange
flow at the H.J. Andrews Experimental Forest, Oregon, USA. Hydrological
Processes, 19(15): 2931-2949.
Gooseff, MN, J LaNier, R Haggerty, and K Kokkeler. 2005. Determining in-channel (dead zone) transient storage by comparing solute transport in a bedrock channel-alluvial channel sequence, Oregon. Water Resources Research, 41, W06014, doi:10.1029/2004WR003513.
Wondzell, SM. 2006. Effect of morphology and discharge on hyporheic exchange flows in two small streams in the Cascade Mountains of Oregon, USA. Hydrological Processes, 20(2): 267-287.
M. N., R. Haggerty, J. LaNier, J. K. Anderson, and S. M. Wondzell. In
review. Common ground in Hyporheic exchange studies: Corroborating
memory functions from groundwater flow and stream solute transport
modeling. Water Resources Research.
Gooseff, M. N., R. Haggerty, S. M. Wondzell, and J. K. Anderson. 2002. Characterizing the cascade effect of upstream hyporheic exchange in mountain streams. Geological Society of America Cordilleran Spring Meeting, Corvallis, OR.
J. K., S. M. Wondzell, and M. N. Gooseff. 2002. Stream
geomorphology, water surface slope, and implications for patterns in
hyporheic exchange flow. Geological Society of America Cordilleran
Section Meeting, Corvallis, OR.
J. K., and S. M. Wondzell. 2002. Stream
geomorphology, bed topography, and implications for patterns in
hyporheic exchange flow. North American
Benthological Society Annual Meeting, Pittsburgh, PA.
Wondzell, and T. Kasahara. 2002. Influence
of channel morphology on hyporheic zones in mountain streams. North American
Benthological Society Annual Meeting, Pittsburgh, PA.
MN, R Haggerty, J LaNier, JK Anderson, SM Wondzell. 2002. Investigating
stream longitudinal geomorphic variability and hyporheic exchange
residence time distribution using a groundwater flow model. American
Geophysical Union Fall Meeting, San Francisco, CA.
S. M., and R. Haggerty. 2002. Evaluating
the importance of the hyporehic zone throughout a 5th-order mountain
stream network. American Geophysical Union Fall Meeting, San
S. M., R. Haggerty, and M. N. Gooseff. 2003. Hyporheic
exchange flows and their residence-time distributions in mountain
streams. Geological Society of America Meeting, Seattle, WA.
Wondzell, S. M., J. LaNier, R. Haggerty, and M. N. Gooseff. 2003. Reliability of groundwater flow models of the hyporehic zone of small mountain streams. American Geophysical Union Fall Meeting, San Fracisco, CA.
This project is funded through the National Science Foundation's Geosciences Directorate (EAR-9909564).