ABSTRACT
A combined hydraulic and hydrogeochemical approach is helping to improve our understanding of a perturbed multi-layer aquifer system in the Northern Adelaide Plains, South Australia. Excessive groundwater pumping from a confined Tertiary carbonate aquifer has reversed the historical upward hydraulic gradient. Although significant contamination has occurred by leakage through leaky wells, large scale leakage through a confining layer does not appear to be significant. Carbon-14 activities verify the original groundwater flow direction. Stable isotopes of water reveal that although subsurface flow from the adjacent mountain ranges is the dominant recharge mechanism, areas missing an important confining layer also receive a significant amount of evaporated water. The stable isotopes of water, together with Cl concentrations, reveal climatic changes over the past tens of thousands of years. Groundwater chemistry is predominantly affected by evapotranspiration. Carbon-13 and strontium isotopes indicate that carbonate mineral dissolution is also an important geochemical process.
