13 Recent Trends in Environmental Geology

Monday, 22 April 2024
8:00 AM - 12:00 PM
Coco Ballroom, Oasis CC

USING HEAT AND SALINITY AS SIMULTANEOUS NATURAL TRACERS TO QUANTIFY RECHARGE IN THE TRINITY RIVER ALLUVIAL AQUIFER, TEXAS, USA

Paper number: 13-4
Program: Theme Sessions
Time: 9:00 AM – 9:20 AM

Authors

  • Tom Brikowski Presenting Author
    The University of Texas at Dallas, ROC21, Richardson, TX
  • Fatemeh Karimi
    The University of Texas at Dallas, ROC21, Richardson, TX

Abstract

Increasing water demand and scarcity is raising the importance of alluvial aquifers, which are heavily influenced by groundwater-surface water interaction. Successful management of water supply and quality depends on accurate knowledge of the water balance, particularly given the frequent exchange of water and potential contaminants between surface and subsurface environments. More crucial for future management is understanding likely effects of climate change and urbanization on that balance.

The Trinity River in Texas supplies drinking water for over 15 million people in the two largest metropolitan areas in the state. Its underlying alluvial aquifer (TRAA), consisting of ≤50 m thick Quaternary alluvial silt, sand and gravel capped by ≤10 m of black vertisol soil, holds 20 times the river's total annual discharge.

Monitoring at a shallow borehole in the upper reaches of the TRAA reveals episodic variation in groundwater salinity and temperature. The borehole is open to 2 meters of TRAA at 6 meters depth, 25 meters from a stream, 150 m down gradient from a periodically desiccated wetland. During a recent overbank flood, stream and borehole water levels rose 0.5 and 2.5 hours, respectively after the onset of precipitation. Within 8 hours borehole electrical conductivity rose 5\% , and from 23-56 hours borehole temperature rose by 0.5°C while salinity continued a steady decline. These variations can be related to simultaneous lateral infiltration from the upstream wetland and vertical infiltration driven by the flood. Initial analysis indicates a saline plume from the desiccated wetland traveled to the borehole via combined surface/subsurface pathways at 75-440 m/day. The temperature rise reflects an infiltration front with initial velocity 10-30 cm/day. Both transport phenomena likely reflect discrete transport pathways, with buried sand channels enhancing lateral transport and deep vertisol soil cracks enhancing vertical infiltration. Quantitative analysis of recharge volumes via these two pathways at this site awaits completion of detailed numerical models.

Such detailed observations of complex recharge processes provide an important constraint for regional models of water supply and quantity, and are crucial for integrated water resource management in these settings.

Geological Society of America Abstracts with Programs. Vol. 56, No. 3

doi: 10.1130/abs/2024NC-398858

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.