DETERMINING GROUNDWATER INFLUENCE TO THE GUADALUPE RIVER BY SPRING DELINEATION AND SPATIAL VARIABILITY OF KARST DEVELOPMENT IN KENDALL COUNTY, SOUTH-CENTRAL TEXAS

Significant karst springs discharge from the underlying Trinity and contiguous Edwards-Trinity aquifers along a 90 kilometer stretch of the Guadalupe River between Comfort, Texas and Canyon Lake. Spring delineation is possible by utilizing a YSI multi-parameter sonde coupled with a GPS to map variations of physicochemical parameters of the Guadalupe River. The sonde and two Solinst LTC Leveloggers were towed behind kayaks through three traverses of the river while continuously recording physicochemical parameters of conductivity, dissolved oxygen, pH, resistivity, salinity, temperature, total dissolved solids, and turbidity. The Marsh McBirney 2000 Flo-Mate electromagnetic flow meter was employed every five kilometers through the study area for stream gauging to quantify spring discharge contributions to total river flow. All data collected from the sonde and leveloggers was processed using Spatial Analyses in ArcGis, specifically inverse distance weighted analyses, to delineate spatial variability of physicochemical anomalies associated with the karst springs and fluvial contributions to river chemistry. Comparison of spatial variability or river chemistry suggests numerous springs discharge subaqueously through conduits and fractures of the aquifers into the Guadalupe River, with several major springs contributing significantly. Additional sampling is scheduled to precisely delineate spring discharge sites along the river, including assessment of major cations and anions, to develop models of the complex karst geomorphic landscape and groundwater framework in the Guadalupe River Basin with reference to the speleogenetic and hydrogeologic evolution of Kendall County, Texas. This research supports the coupling of spatial analyses with physicochemical characteristics in identifying groundwater contribution to fluvial systems in similar karst regions.