Seasonal to Decadal Variability in Focused Groundwater and Contaminant Discharge along a Channelized Stream

Ganesh N. Tripathi, Alan E. Fryar, Steven K. Hampson, Abhijit Mukherjee

Research output: Contribution to journalArticlepeer-review

Abstract

Focused groundwater discharge to streams is problematic at contaminated sites because high fluxes can limit natural attenuation in the hyporheic zone. However, information on location, spatial evolution, and temporal persistence of springs in unlithified sediments over multiyear time scales is limited. We examine discharge at point (~1-m) to reach (~300-m) scales along a stream that intercepts trichloroethene and technetium-99 plumes from a Superfund site. During 2011 to 2012, we seasonally monitored stream and spring flow and contaminant concentrations, along with probing streambed temperatures on a grid in winter and summer, building on prior monitoring during 1999 to 2002. Baseflow measured by both gauging and dye dilution generally increased with distance downstream, and stream and spring discharge varied seasonally, from minima in October to January to maxima in February to June. Thermal anomalies identified by probing occupied approximately 3% to 6% of the reach and typically coincided with visible springs or seeps. Locations of anomalies were similar to those identified in summer 2002, although some orifices disappeared and others emerged. Vertical groundwater fluxes calculated from probing tended to be less than net fluxes calculated from stream discharge, perhaps in part because the assumption of one-dimensional, steady-state flow in calculating point fluxes was simplistic. Maximum contaminant concentrations and fluxes decreased between 1999 to 2001 and 2011 to 2012 as a result of partial capture by an upgradient pump-and-treat system. Our findings confirm that springs in unlithified sediments can remain stationary within a few meters over decadal time scales, and seasonal variability in discharge can be greater than decadal variability.

Original languageEnglish
Pages (from-to)32-45
Number of pages14
JournalGround Water Monitoring and Remediation
Volume41
Issue number1
DOIs
StatePublished - Jan 1 2021

Bibliographical note

Funding Information:
This work was funded by DOE through the Kentucky Research Consortium for Energy and Environment. However, the contents of the paper do not necessarily reflect the views and policies of DOE. We thank DOE, TVA, and the Kentucky Department of Fish and Wildlife Resources for providing access; Brian Begley (Kentucky Department for Environmental Protection) for providing data; Jim Currens (KGS) for help with dye analyses; and Kelley Lynn, Steve Meiners, Brandon Dailey, Jeremy Paessler, and Ahmed Fekri for assistance with field work. Claudia Varnier and Ty Ferré provided helpful review comments on the paper. Data are available upon request from A.E. Fryar.

Funding Information:
This work was funded by DOE through the Kentucky Research Consortium for Energy and Environment. However, the contents of the paper do not necessarily reflect the views and policies of DOE. We thank DOE, TVA, and the Kentucky Department of Fish and Wildlife Resources for providing access; Brian Begley (Kentucky Department for Environmental Protection) for providing data; Jim Currens (KGS) for help with dye analyses; and Kelley Lynn, Steve Meiners, Brandon Dailey, Jeremy Paessler, and Ahmed Fekri for assistance with field work. Claudia Varnier and Ty Ferr? provided helpful review comments on the paper. Data are available upon request from A.E. Fryar.

Publisher Copyright:
© 2020, The Author(s). Groundwater Monitoring & Remediation © 2020, National Ground Water Association

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Water Science and Technology

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