Summary of Findings: Upper Onion Creek Dye Trace, Hays County, Texas, Winter 2017

Topic: Groundwater Tracing and Groundwater Flow Studies
Source: Interagency memo
Format: Tech Note
Year: 2018

A consortium of central Texas agencies and groundwater scientists conducted a series of studies of the Trinity Aquifers that culminated in publication of the Hydrogeologic Atlas of the Hill Country Trinity Aquifer (Wierman et al., 2010). A continuation of those studies has revealed a hydrologic connection between the Middle Trinity Aquifer and the Blanco River and portions of Upper Onion Creek (Hunt et al., 2016; 2017).

An initial phase of dye tracing in the vicinity of Dripping Springs began in December, 2017 as a continuation of the previous work on surface water and groundwater interactions in Onion Creek. The study was designed to help delineate recharge areas, groundwater flow paths and travel times, and to identify potential sources to springs discharging within the basin. The study lasted for approximately five months, with the final samples collected in April 2018. An interagency memo was published in January 2018 that provided initial results of this study (IM, 2018). This memo provides a complete summary of the data and findings as the study has concluded.