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East Alligator district centre water supply assessment : Kakadu National Park



East Alligator district centre water supply assessment : Kakadu National Park

Other title

D . Pidsley


Jamieson, M.; Pidsley, D.; Paiva, Jerome


E-Publications; E-Books; PublicationNT; Technical Report ; 26/1991




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






Water-supply -- Northern Territory -- Kakadu National Park; Groundwater -- Northern Territory -- Kakadu National Park; Kakadu National Park (N.T.)

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Power and Water Authority

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Technical Report ; 26/1991


1 v. : ill., maps ; 30 cm.

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Technical Report WRD91026 Viewed at 15:07:48 on 29/07/2010 Page 37 of 107. 4. ASSESS!.jENT OF WATER RESOURCES 4.1 CLUfATE The East Alligator River region has a monsoonal climate. Virtually all the rainfall occurs in the wet season, which varies in length a.nd intensity of rainfall from year to year. The 'wet' is generally confined to the NO'Tember-March period wi th October and April tending to be transitional months. The dry season lasts from about May to September. Rainfall has been recorded at the :;:ast Alligator ranger station since October 1984 (see Table 4.1). The average yearly rainfall since this time is about 1350 mm. Rainfall has been recorded at nearby Oenpelli since 1910, resulting in an average annual rainfall of 1300 mm (Reference 7). It appears that rainfall in recent years at East Alligator b.as been typical for this area. 4.2 HYDROGEOLOGZ The area is locat'ad in the north east part of the Pine Creek Geosyncline. The fractured zone of District Centre sits atop the weathered and the Bulman Fault, which runs north west to south east (see Di.agram 4). Water from bores in the Kombolgie Sandstone Formation is usually very corrosive due to low alkalini ty and low pH (see Section 2.4). The area just to the north and west of the District Centre is underlain by the Koolpin Formation.. This is mostly dolomitic siltstonE> and schist. Water from this formation has a greatE>r alkalinity usually and is only slightly corrosive. The yield from bores in the Koolpin is usually low, up to about 1 Lis due to the low primary poros i ty of the formation and much of the secondary voids having been filled with clays. For a description of bores drilled into the Kombolgie and Koolpin formations in this area, see Appendix 4. 4.3 PRODUCTION HISTORY There has been no record kept of pumping figures at East Alliga tor. The bores are equipped with meters but no readings have been recorded. There is also no record of the length of time that the bores are operated each day. However, RN 23449 or 005~\J