Dynamics of Hyporheic Flow and Heat Transport Across a Bed-to-Bank Continuum in a Large Regulated River

Authors

Katelyn E. Gerecht, Smith College
M. Bayani Cardenas, The University of Texas at Austin
Andrew J. Guswa, Smith CollegeFollow
Audrey H. Sawyer, The University of Texas at Austin
John D. Nowinski, The University of Texas at Austin
Travis E. Swanson, The University of Texas at Austin

Document Type

Article

Publication Date

3-29-2011

Publication Title

Water Resources Research

Abstract

The lower Colorado River (LCR) near Austin, Texas is heavily regulated for hydropower generation. Daily water releases from a dam located 23 km upstream of our study site in the LCR caused the stage to fluctuate by more than 1.5 m about a mean depth of 1.3 m. As a result, the river switches from gaining to losing over a dam storage-release cycle, driving exchange between river water and groundwater. We assessed the hydrologic impacts of this by simultaneous temperature and head monitoring across a bed-to-bank transect. River-groundwater exchange flux is largest close to the bank and decreases away from the bank. Correspondingly, both the depth of the hyporheic zone and the exchange time are largest close to the bank. Adjacent to the bank, the streambed head response is hysteretic, with the hysteresis disappearing with distance from the bank, indicating that transient bank storage affects the magnitude and direction of vertical exchange close to the bank. Pronounced changes in streambed temperature are observed down to a meter. When the river stage is high, which coincides with when the river is coldest, downward advection of heat from a previous cycles' warm-water pulse warms the streambed. When the river is at its lowest stage but warmest temperature, upwelling groundwater cools the streambed. Future research should consider and focus on a more thorough understanding of the impacts of dam regulation on the hydrologic, thermal, biogeochemical, and ecologic dynamics of rivers and their hyporheic and riparian zones.

Volume

47

Issue

3

DOI

10.1029/2010WR009794

ISSN

00431397

Rights

Copyright 2011 by the American Geophysical Union

Comments

Archived as published.

Recommended Citation

Gerecht, Katelyn E.; Cardenas, M. Bayani; Guswa, Andrew J.; Sawyer, Audrey H.; Nowinski, John D.; and Swanson, Travis E., "Dynamics of Hyporheic Flow and Heat Transport Across a Bed-to-Bank Continuum in a Large Regulated River" (2011). Engineering: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/egr_facpubs/33