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Changes in sources and storage in a karst aquifer during a transition from drought to wet conditions

Journal of Hydrology

By:
, , ,
DOI: 10.1016/j.jhydrol.2012.08.030

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Abstract

Understanding the sources and processes that control groundwater compositions and the timing and magnitude of groundwater vulnerability to potential surface-water contamination under varying meteorologic conditions is critical to informing groundwater protection policies and practices. This is especially true in karst terrains, where infiltrating surface water can rapidly affect groundwater quality. We analyzed the evolution of groundwater compositions (major ions and Sr isotopes) during the transition from extreme drought to wetconditions, and used inverse geochemical modeling (PHREEQC) to constrain controls on groundwater compositions during this evolution. Spring water and groundwater from two wells dominantly receiving diffuse and conduit flow (termed diffuse site and conduit site, respectively) in the Barton Springs segment of the Edwards aquifer (central Texas, USA) and surface water from losing streams that recharge the aquifer were sampled every 3–4 weeks during November 2008–March 2010. During this period, water compositions at the spring and conduit sites changed rapidly but there was no change at the diffuse site, illustrating the dual nature (i.e., diffuse vs. conduit) of flow in this karst system. Geochemical modeling demonstrated that, within a month of the onset of wetconditions, the majority of spring water and groundwater at the conduit site was composed of surface water, providing quantitative information on the timing and magnitude of the vulnerability of groundwater to potential surface-water contamination. The temporal pattern of increasing spring discharge and changing pattern of covariation between spring discharge and surface-water (steam) recharge indicates that that there were two modes of aquifer response—one with a small amount of storage and a second that accommodates more storage.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Changes in sources and storage in a karst aquifer during a transition from drought to wet conditions
Series title:
Journal of Hydrology
DOI:
10.1016/j.jhydrol.2012.08.030
Volume
468-469
Year Published:
2012
Language:
English
Publisher:
Elsevier
Publisher location:
Amsterdam, Netherlands
Contributing office(s):
Texas Water Science Center
Description:
14 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
159
Last page:
172
Country:
United States
State:
Texas