An investigation of recharge to the Namoi Valley aquifers using environmental isotopes

Abstract

Environmental tritium and radiocarbon were used to study aspects of groundwater origin, transport and mixing in the complex aquifer system underlying the Namoi Valley, N.S.W. A substantial proportion of the water in the upper aquifer (depth less than 25 m) percolated underground in the post-nuclear period (after 1955). The observed relationship between ä13C value and distance is evidence for riverwater recharge in the upper aquifer. There is evidence that water in the middle aquifer system (depth 50-75 m) percolated underground about 600 years ago. Finally, it is suggested that water from the Great Artesian Basin leaks into the deeper water of the lower aquifer system.