Good predictive models of infiltration and recharge through the vadose zone in karst systems are required for improving groundwater models and sustainable management policies in karst regions. The goal of this study was to estimate annual recharge rates and quantify how cumulative environmental effects, and their timing, influence epikarst infiltration and recharge in the karstic Trinity Aquifer of the central Texas Hill Country. The Trinity Aquifer is the most important groundwater resource for communities and private well owners in the region, and as the region's population grows, increased demands for groundwater are causing spring-fed streams to cease flowing, wells to run dry, and large portions of the population are facing water shortages, especially during drought periods. Stable isotope and hydrologic data from Cave Without A Name, near Boerne, TX, allowed me to quantify relationships between recharge and antecedent moisture conditions, environmental parameters, and rainfall characteristics.