Alice Springs is an important centre for regional industry, tourism and transport in the Northern Territory. The town has approximately 29,000 inhabitants and 400,000+ visitors are wholly reliant on groundwater from aquifers in the Amadeus Basin. Current groundwater use in the Roe Creek Management Zone borefield is ~8,500 ML/yr, far in excess of the ~750 ML/yr of groundwater recharge to the area. As a result, groundwater levels in the Roe Creek borefield have fallen by ~1 m/yr since 1964.
As part of the Exploring for the Future program, Geoscience Australia flew ~2375 line km of AEM, drilled 3 boreholes, took 34 SNMR readings and collected 21 groundwater samples for hydrogeochemical analysis in the Alice Springs project area. Hydrochemistry samples were analysed for major and minor chemistry, stable isotopes, carbon-14, chlorine-36, tritium, CFCs and SF6. In addition DENR NT have drilled a number of deep (500m) groundwater bores to analyse hydrogeochemistry and to monitor groundwater levels.
Over the last 40 years, there have been at least 4 generations of groundwater sampling for chemistry, stable isotopes and radioisotopes in the Amadeus Basin. The earliest samples were collected by Calf in 1978, followed by Jacobson in 1989, BRS in 1999-2000 and Geoscience Australia in 2017-18.
During this period there have been at least 12 large rainfall events (> 150mm), although only the anomalously wet year of 1974 showed significant groundwater recharge in the Amadeus Basin, the water table has fallen by over 40 metres and many additional bores have been drilled or deepened. In addition, many older bores were indifferently constructed while modern bores are targeted to specific aquifers and intervals. This paper looks at how these changes are reflected in groundwater hydrochemistry and isotopic values and what these changes may mean to the management of groundwater in Alice Springs.