Alice Springs town basin, review 2003
Read, R. E.
E-Publications; E-Books; PublicationNT; Report ; no. 42/2003
2003-12-01
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Date:2003-12
English
Department of Infrastructure, Planning and Environment
Alice Springs
Report ; no. 42/2003
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https://hdl.handle.net/10070/229443
https://hdl.handle.net/10070/672980
6.4.4.1 Proposed rehabilitation of the Heavitree Gap Area Pumping the saline water out of this part of the aquifer to restore it as a useful resource has been proposed (G. Ride pers. comm.). Taking the boundaries shown in Figure 36 the volume of saturated sediments and water stored are shown in Table 16. RN 14196 has a recommended pumping rate of 9 L/s. There is no data recorded for RN 10990. RN 7506 has data for an extended pumping test, but no measurements for the bore itself. Table 16, estimated volumes of saline water in the Heavitree Gap area Volume of saturated sediment m3 Estimated volume of saline water ML (1) All sediments 8 600 000 2 600 Sand aquifer only 5 600 000 1 700 (1) Porosity is assumed to be 0.3 7375000 7376000 7377000 383000 384000 385000 386000 7506 10990 14196 Approximate limit of saturated sediments Approximate limit of sand aquifer Approximate limit of saline water Historic production bores Existing production bore, not equipped Figure 36 Heavitree Gap Area By the most optimistic assessment, to flush saline water from the sand aquifer only, at least 6 years of continuous pumping at 9 L/s (280 ML/year) would be needed. In practise it would take longer as saline water from the adjacent lower permeability sediments continued to drain into the sand aquifer, and there would be significant mixing of the fresh and saline water. Disposal of 280 ML/year of water ranging from 2000 mg/L to 5000 mg/L would be a problem. One possibility would be pumping to ornamental lakes (G. Ride pers. comm.). Annual evaporation is about 3000 mm/year, but minimum monthly evaporation is only 100 mm. Therefore 25 ha of water surface would be needed to dispose of this much water. Alternatively if a field of two or three bores was used to take advantage of the higher evaporation rates in summer only 10 ha of evaporation ponds would be needed. If the average TDS of the input water was 3000 mg/L after six years of evaporating it in a 1 m deep lake the TDS would be about 50000 mg/L, that is just above that of seawater. 59