Tracing Groundwater Flowpaths in Kinney County, Texas

Author S Johnson and G Schindel
Year 2015
Description This report presents the findings of a groundwater flowpath investigation in Kinney County, Texas, performed by the Edwards Aquifer Authority between 2007 and 2012.
Report Number 15-02
Publisher Edwards Aquifer Authority
Location Edwards Aquifer, Balcones Fault Zone, San Antonio Segment, Kinney County
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Results of the investigation revealed discrete groundwater flowpaths and relatively slow to rapid
groundwater velocities connecting the injection points to wells and springs. Apparent velocities from the injection point to each detection site ranged from two ft/d (one m/d) to 4,458 ft/d (1,367 m/d). These are straightline distances between dye injection and recovery points divided by travel time until the first detection of dye.

Because the actual groundwater flowpaths are certainly longer than straight lines, the apparent velocities underestimate the actual velocities. Injection points were Alamo Village Cave, HF&F Cave, Grass Valley PW-1, Whitney Cave, and Pratt’s Sink in the north part of the study area; Dooley Irrigation Well in Pinto Valley; and Boerschig Well located approximately two mi northwest of Brackettville. Dyes from Grass Valley PW-1, Whitney Cave, and Pratt’s Sink traveled radially to the south, east, and west, influenced by a structural embayment in the Edwards Aquifer that maintained relatively flat groundwater gradients. Deep flowpaths probably influenced by geologic structures resembling anticlines carried dyes southward to Las Moras Springs, a City of Brackettville well, and Fort Clark Municipal Utility District (MUD) wells. Groundwater chemical compositions vary at these locations, suggesting that there are discrete
flowpaths to each one. Dye from Alamo Village Cave traveled to Pinto Springs. Dye from HF&F Cave was detected in few locations. Dyes from the Boerschig Well were detected at Las Moras Springs, a City of Brackettville well, and Fort Clark MUD wells, although the detections seemed to change with groundwater head, Las Moras Springs discharge, or other factors. Igneous intrusions near Las Moras Mountain created a barrier to groundwater flow and diverted dyes westward toward Pinto Valley.