High water tables following an extensive wet season provided a unique opportunity to evaluate groundwater baseflow to rivers and coastal zones from the Burdekin River Delta aquifer. This region is one of the largest irrigation districts in Australia and relies, in part, on groundwater extraction. However, because of the complex nature of the aquifer, it is difficult to evaluate groundwater discharge to rivers and coastal zones using traditional hydraulic techniques. In 2003-04, Cook et al. (2004) evaluated groundwater baseflow to rivers in the Burdekin region using radon. In addition, they evaluated submarine groundwater discharge to Bowling Green Bay, an important outlet for the Burdekin aquifer, using radon and the radium quartet (223Ra, 224Ra, 226Ra, 228Ra). Radon and radium are naturally occurring radioisotopes that tend to be enriched in groundwater relative to receiving surface waters. This property makes them ideal tracers to quantify groundwater discharge.