USING GEOCHEMICAL AND STATISTICAL ANALYSES TO IDENTIFY LOCAL AND REGIONAL FLOW TO A MULTI-OUTLET SPRING SYSTEM: SAN SOLOMON SPRINGS, TEXAS, USA

Effective water management requires that source areas to springs in arid and semi-arid environments be characterized well enough to assess impacts on flow from changes in recharge and groundwater withdrawals. Geochemical signatures of groundwater can be used as indicators of different components of flow to springs and can be especially useful for characterizing different sources that contribute to multi-outlet spring systems. San Solomon Springs in Trans-Pecos Texas provides an example of a multi-outlet spring system in a karstic landscape with potentially different source areas. Samples from each of the six named orifices at San Solomon Springs were collected in 2019 and 2020 and combined with historical data to assess the geochemical signatures of the spring system. Results of analyses of field parameters, ions and trace elements, and multiple stable and radiogenic isotopes were combined with multivariate statistical analyses to investigate the hydraulic relationships among the individual springs of San Solomon Springs.

Results show that all six spring outlets are represented by Na-Cl-SO₄ hydrochemical facies. Isotopic compositions of all six springs are consistent with a conceptual model of older groundwater (likely of Pleistocene age) from a regional flow system that upwells through carbonates and alluvial sediments to discharge at the springs. Elevated ion concentrations and carbon isotopes in East Sandia and West Sandia springs indicate mixing of water, added by either irrigation return flow or precipitation, through alluvial sediments impacts flows at both spring outlets. Saragosa Spring is likely a seepage spring and is more heavily influenced by a near surface component (e.g., irrigation or precipitation). A subset of records for San Solomon, Phantom Lake, and Giffin springs indicating elevated ³H and NO₃^- and lower ion concentrations suggest precipitation also enters the regional system as local recharge. Statistical analyses using major ion chemistry alone effectively identify as many as four different flow components to the spring system. Isotopic and trace element data complement the statistical analyses and are consistent with multiple sources of flow to the springs.