SPRINGSHED DELINEATION FOR THE DOWNTOWN SALADO SPRING COMPLEX, SALADO, TEXAS

The growing population along the Northern Segment of the Edwards Balcones Fault Zone Aquifer will correspondingly increase groundwater demand and environmental stresses on the aquifer, which could impact local springs that provide habitat for the threatened Salado salamander (Eurycea chisolmensis). This study focuses on the Downtown Salado Spring Complex (DSSC) in central Texas to define the springshed boundary and identify important recharge zones. An improved understanding of the hydrogeology within this springshed will support groundwater management and thereby help to protect the aquifer and the Salado salamander.

Four different approaches were used in this study. First, synoptic water-level measurements collected in 2010, 2013, and 2019 in Bell County were used to hypothesize an appropriate springshed boundary for the DSSC. The springshed boundary was interpreted from available data and may change under different hydrologic conditions. Due to flow path variability characteristic of karst aquifers, the synoptic maps are being analyzed in conjunction with field observations of aquifer outcrops, hydrograph correlations, and groundwater chemistry. Rainfall and springflow across the creek basin are being analyzed through a statistical correlation to understand if there are areas within the springshed where rainfall causes a greater response to springflow than in other areas. Water samples were collected from springs at the DSSC and three wells within the creek basin during different aquifer conditions to determine their ionic chemistry and isotopic composition for a better understanding of the flow system.

The resulting ionic chemistry and isotopic composition of the samples confirm interpretations made from the estimated springshed boundary. The calcium-bicarbonate water sourced from the wells upgradient in the springshed appears similar to the water chemistry at the springs. A sodium-bicarbonate water sourced from a well outside of the estimated springshed boundary provides evidence of a different flow path that does not contribute to discharge at the DSSC. Additionally, radiocarbon dating of the samples present apparent age patterns that support the general springshed boundary and the flow system interpretation.