The use of stable isotopes of oxygen and deuterium in dryland salinity studies in eastern New South Wales

Various hydrogeochemical processes occur when groundwater from a fractured-bedrock aquifer discharges through clay-rich debris flow deposits. Reactions within colluvium include: ion exchange of calcium for sodium in basal clays; dissolution of sodium chloride from dust-derived salt particles in the clay-rich colluvium and redox reactions. The increased dryland salinisation problems in Australia are attributed to evaporative concentration of groundwaters in discharge zone. An application of the stable isotopes oxygen-18 and deuterium in hydrogeochemical studies in the Yass and Wagga Wagga areas have shown that the salinisation cannot be accounted for by evaporative concentration. Hydrogeochemical processes in the mixing zone between bedrock groundwaters discharging under artesian pressure and colluvium are responsible for the development of salinisation processes