Alice Springs town basin, review 2003
Read, R. E.
E-Publications; E-Books; PublicationNT; Report ; no. 42/2003
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Department of Infrastructure, Planning and Environment
Report ; no. 42/2003
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rate by 15 ML per month for each month without recharge. As stated withdrawal would be 0 in the eighth month, and only 400 ML would have been extracted. 400 600 800 1000 1200 Annual draught in ML 0.8 0.6 0.4 0.2 0 D ec lin e i n m 19 53 19 54 19 55 19 56 19 57 19 58 19 59 19 60 19 61 Line used by Forbes (1962) to estimate y ield for zero decline. Figure 31 Water level decline versus draft, 1953 to 1961, after Forbes (1962) Macqueen (1976) estimated the safe yield of the basin to be 660 ML/year, 300 ML/year from the Northern Zone and 360 ML/year from the Southern Zone. Macqueens model related groundwater recharge to water level below the Todd. Pumping at average rates more than this has left water levels at above desirable levels. SKM (2001) estimated median annual recharge as 840 ML/year. SKMs calculations assume that recharge is independent of water level, which is doubtful. SKM (2001) have also attempted estimates of the time that it would take for water levels to reach the minimum allowable of 8 m below the river bank. These are in Table 13 . Table 13 Extraction rate against time to minimum, after SKM (2001) Figure 5-2. Extraction rate ML/year Estimated years for water level to reach the minimum, assuming annual recharge of 840 ML/year. 1 650 4 1 500 5 1 250 8 1 000 21 From the above it would be reasonable to raise extraction rates to the range 1000 to 1250 ML/year. This would appear to make good use of the resource, lower nuisance water tables with a reasonable usage rate of production bores. SKM (2001) did not divide extraction between zones. Extraction from the Northern Zone should be 350 ML/year, and the balance from the Southern Zone. 53