119 Recent Investigations of the Hydrogeology Edwards (Balcones Fault Zone) Aquifer, the Trinity (Hill Country) Aquifer, and Their Interactions, South-Central Texas

Recent research into the hydrogeological characteristics of the Edwards (Balcones Fault Zone) and/or Trinity (Hill Country) aquifers, south-central Texas, including their inter-aquifer connections, vulnerability, and prospects for long-term sustainability given changes in population, land use, and climate of the region.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 209

Revisiting Puente 1978: Interpreting the foundational Edwards Aquifer recharge dataset in light of contemporary understanding of Edwards-Trinity interactions

Paper number: 119-6
Program: Technical Sessions
Time: 2:55 PM – 3:10 PM

Authors

Abstract

The U.S. Geological Survey (USGS) estimates total annual recharge to the Edwards Balcones Fault Zone (Edwards) Aquifer using the “Puente method,” a hydrograph-based approach formally described in 1978. Despite advances in understanding Edwards-Trinity interactions, this recharge estimation method has remained largely unchanged for nearly fifty years, and its results continue to guide regional modeling and water management.

Here we redevelop the basic approach used in the Puente method and recast it in modern terms. Implicitly, the Puente method is a collection of steady-state water-balance models of the major catchments dissecting the recharge zone. Monthly recharge in each catchment is estimated as the difference between the streamflow into and out of the recharge zone, plus a third term, SI, that accounts for autogenic (sourced from recharge zone rainfall) runoff and recharge. We show that SI contributes more than half of total estimated recharge in some basins, yet it is unmeasured. The SI term is derived from manual hydrograph separation techniques that, we show, rely on assumptions that may conflict with current understanding of Edwards Aquifer contributing zone hydrogeology.

We suggest a framework for updating the Puente method using modern observation networks to provide reproducible, water-balance-based estimates of Edwards Aquifer recharge.

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

doi: 10.1130/abs/2025AM-414031

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