GROUNDWATER TRACING AS A MEANS TO COLLECT DATA FOR GROUNDWATER MODEL DESIGN AND CALIBRATION
To help address this problem, artificial tracers were used to calculate groundwater velocities in the conduits over distances of approximately 300 and 2600 m. Both traces revealed groundwater velocities of between 0.02 and 0.03 m/s, Reynolds Numbers of 105, and nearly identical standardized breakthrough curves. When compared to natural tracer data such as from CFCs, tritium, or tritium/helium-3, which have revealed groundwater ages on the order of decades, these data indicate that the groundwater ages must be a composite of very old water from the aquifer matrix and very young water from the dissolved conduits. Effective groundwater modeling efforts in karst aquifers must, therefore, not rely on composite age dates for travel-time calibration/validation because they do not accurately represent conduit residence times. It is imperative that model designs honor the dual/triple permeability nature of the aquifer using travel-time data collected from the conduits and matrix and/or fracture permeability data collected from other testing methods.