Surface water and groundwater interactions: Cibolo Creek and Guadalupe River, Kendall County, Texas

This study investigates the interaction of the Trinity Aquifer with Cibolo Creek and the Guadalupe River within Kendal County, Texas. A program of water sampling and analysis was undertaken to characterize the water present within these three water bodies. The isotopic and geochemical data generated for each water body was then analyzed to determine possible interactions between the three bodies. Mixing models were used to analyze isotopic data to try and determine end member percent contributions to analyzed waters. Geochemical data on 17 parameters were analyzed by multivariate statistical techniques to determine clustering, groupings, similarities and differences between the analyzed water. From this analysis it was determined that Cibolo Creek bears little relation to the groundwater of the Trinity Aquifer and does not gain water from the aquifer. The similarity of water chemistry between the Guadalupe River and Trinity aquifer indicates that the Guadalupe River gains groundwater along at least some of its reach.