42-18 Fingerprinting Spring Water Sources Using pH, Specific Conductivity, and dissolved inorganic carbon (DIC) Correlation with Elements in the Gibson Jack Watershed

Abstract:

Springs are ecologically and geologically important due to being biologically diverse hotspots and revealing underground formations and bedrock lithology. With current climate changes – rain-snow transition line moving, snow accumulation lessening, and melt times coming earlier – this will affect springs' recharge rates, thus affecting life and water quality downstream. Our goal was to pinpoint the geologic units sources of spring water in the Gibson Jack Watershed in southeastern Idaho to understand the influence of geology on spring water chemistry with implications for downstream chemistry. We hypothesized that dissolved inorganic carbon would be correlated to strontium as an indicator of water-rock reaction. We collected 20 spring water samples during the winter baseflow and analyzed them for pH, specific conductivity, dissolved inorganic carbon (DIC) and elemental compositions using a Thermo iCAP Q ICP-MS. Fifteen springs were associated with quartzites, two with limestones, two with landslide deposits, and one with shale/slate. In contrast to our expectations, DIC was weakly correlated with Sr and U (r²=0.6512), these were the strongest correlations found.  The data showed there were specific groupings based on what lithological unit the spring water was sourced from - the limestone and quartzite made their own distinct groups in many of the elemental analyses based on DIC and ppb levels of the elements. There is an outlier in the quartzite that had high ppb levels of differing elements such as Sr, Ca, Mg, U, and Ti. The landslide deposits indicate a mix between quartzite and shale/slate based on the location and proximity to lithologic groupings. This work can be used in other watersheds in the area to fingerprint spring water sourcing.

© Copyright 2026 The Geological Society of America (GSA), all rights reserved.