Territory Stories

Alice Springs town basin, review 2003



Alice Springs town basin, review 2003


Read, R. E.


E-Publications; E-Books; PublicationNT; Report ; no. 42/2003




Made available via the Publications (Legal Deposit) Act 2004 (NT).





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Department of Infrastructure, Planning and Environment

Place of publication

Alice Springs


Report ; no. 42/2003

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EXECUTIVE SUMMARY The Alice Springs Town Basin has been extensively studied for over 50 years. In earlier times it was the water for Alice Springs, more recently it has become an environmental problem. It is a small alluvial basin recharged primarily from the Todd River, though significant direct infiltration occurs in years of high rainfall such as 1974. The major management problem in the basin is salinity. Over most of the basin salinity has increased dramatically since about 1972. The increase corresponds to the unusually wet period around 1974, which resulted in substantial diffuse recharge and large rises in water table. The consequences of the large recharge event in 2000 are not yet evident, possibly partly due to lack of monitoring. The major management objective should be to increase extraction to nearer the basins maximum. This will have the following benefits: Lowering of water levels will reduce the impacts of high water levels on infrastructure. Pumping induces recharge from the Todd with lowering of water levels, hence extraction in drought periods can lower TDS (total dissolved solids). However large rainfall events result in direct infiltration which moves salt down to the water table increasing TDS. Pumping bores have shown varied and sometimes hard to understand salinity trends. The salinity of bores located close to saline water near the eastern margin has increased with time, and some of those will need to be replaced. An attempt was made to establish a salt balance for the basin. Unfortunately the large uncertainties associated with the rating curve at Heavitree Gap and the very limited set of TDS measurements for flows in the gap have made this impossible at this stage. A conductivity probe is needed on the data logger at the gap. A digital model of the basin is needed to allow better prediction of the effects of siting new bores and the response of the basin to seasonal conditions. Such a model should incorporate salt transport to try to improve understanding and management of the salinity problems. The weathered metamorphic rocks around the edges of the basin contain highly saline water. Without due care development will cause problems with a rising saline water table in some areas. i