2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 70-8
Presentation Time: 3:05 PM

BASEFLOW CONTRIBUTIONS TO THE DEVILS RIVER, TEXAS, USA


BRUECHER, Taylor, Sul Ross State University, Biological, Geological and Physical Sciences, Box C 139, Alpine, TX 79832, URBANCZYK, Kevin M., Department of Biological, Geological and Physical Sciences, Sul Ross State Univ, Box C-139, Alpine, TX 79832 and BENNETT, Jeffery, Rio Grande Wild and Scenic River, National Park Service, BBNP-ScRM, 266 Tecolote Drive, Big Bend National Park, TX 79834

The Devils River flows 105 km (65 mi) through the southwest portion of the Edwards Plateau in Val Verde County, Texas and into Amistad Reservoir and Amistad National Recreation Area (AMIS). Many springs issue from the Cretaceous Edwards-Trinity Plateau Aquifer (ETPA), giving the Devils one of the largest base flows of Texas’ rivers. Low flows of the river are sustained by groundwater inputs, while frontal and convective storms drive high flows. The International Boundary and Water Commission maintains a stream gage near Pafford’s Crossing above the reservoir and monitors flow of the Devils River. Data from 2012 indicates a 40% baseflow increase in the study area.

The Devils is a pristine, unregulated river with exceptional water quality and abundant and native aquatic fauna. Increased urban and energy development leave the Devils River with an uncertain future. Furthermore, extended drought in Texas has elevated the concern and the state climatologist has warned that Texas could be in a drought worse than the drought of record in the 1950s. Protection of the water resources that support a pristine native fishery and a national recreation area requires a deeper understanding of the underlying groundwater resources.

Data collection occurred in five campaigns and revealed significant downriver increases in dishcharge (up to 4.19 m3/s). Water quality analysis of surface and groundwater consisted of field parameters, cation/anion water analysis, stable isotopes, and radiocarbon dating. Percent modern carbon values of springs range from 60.3 +/- 0.2 pmc to 73.2 +/- 0.3 pmc, and δ13C values range from -15.2 ‰ to -17.3‰. Field measurement averages for springs include values of specific conductivity (491 µS/cm), temperature (22.16 °C), pH (7.4), and dissolved oxygen (5.6 mg/L). Surface water average values include specific conductivity (421 µS/cm), temperature (27.06 °C), pH (8.00), and dissolved oxygen (7.70 mg/L). This study provides a greater understanding of groundwater flow paths, recharge areas, the effects of regional structure, and the influence springs have on water quality and quantity in the Devils River.

Session No. 70

T51. Geology and Hydrology of the National Parks: Research, Mapping, and Resource Management II
Sunday, 19 October 2014: 1:00 PM-5:00 PM
214 (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.186
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