39-2 Springs Under the Influence of Surface Water: Integrating Traditional and Novel Parameters to Characterize Groundwater-Surface Water Interactions

Session: Understanding Karst Hydrology and Karst Aquifers Using Innovative Tracers and Other Technologies

Presenting Author:

Authors:

Abstract:

Stillhouse Hollow and Belton Reservoirs were initially constructed in Bell County, Texas, for water storage to mitigate the impacts of high stream flow conditions and to supplement water supplies during droughts. These impoundments artificially raise water levels that may cause seepage into underlying aquifers, creating new springs or changing conditions in existing springs. The exponential growth along the I-35 corridor increases the need for managing water resources more efficiently and to better understand groundwater-surface water interactions.  

In this study, traditional hydrogeochemical parameters were integrated with environmental DNA (eDNA) detection to confirm and document surface water influence in karst springs.  While all measured parameters confirm some degree of groundwater-surface water interaction, additional sampling provided new insights. Conventional in-situ water quality measurements enabled quick comparisons of sites sampled. Ionic sample analysis confirmed the chemical composition of the regional geology while identifying changes in ionic composition as a function of groundwater-surface water interaction in high-flow versus low-flow conditions. Analysis of δ18O and δ2H values throughout the study period highlighted the variability and degree of groundwater-surface water interactions at each site. Detection of zebra mussel eDNA at sample sites, a novel application of eDNA in hydrogeology, confirms the presence of surface water at each site. Research in the area confirmed a high degree of seasonal variation in the groundwater-surface water interactions and revealed different flow paths connecting the reservoirs and springs. Our results indicate that taking a multi-parameter approach is necessary when investigating karst aquifers as certain methods are more appropriate under different flow conditions.

While reservoirs are currently meeting water demands, continued growth in Central Texas strains water resources for future generations. The multi-parameter approach demonstrated in this study supports resource management through gaining a more nuanced understanding of interactions between surface reservoirs constructed in the vicinity of karst aquifers.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7412

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.