Aquaculture Groundwater Resource Atlas - Bonaparte Basin

Overview

The onshore Bonaparte Basin extends from Cambridge Gulf and Joseph Bonaparte Gulf southwards to Kununurra. The main aquifers are the Permian Keep Inlet Formation, the dolomitic limestones in the Devonian Ningbing Group, and the Ord River alluvium.

The groundwater potential of Devonian-Carboniferous sandstones is not known, but they are unlikely to be significant aquifers. Groundwater in Cambrian and Precambrian rocks is restricted to fractures, and these rocks have low prospectivity.

Major aquifers in the Bonaparte Basin

Typically high yielding aquifers are shown in blue.

Keep Inlet Formation

The main aquifer in the basin is the Permian Keep Inlet Formation of late Carboniferous to Early Permian age. The formation is not exposed at the surface, but occurs in the subsurface north of the Weaber Range, extending offshore beneath the tidal flats. It has been penetrated by the oil exploration wells Bonaparte 1, Keep River 1 which is approximately 9km east of the Western Australia/Northern Territories border, and Spirit Hills 1 which is approximately 25 km east of the border.

The formation consists of sandstone, shale and minor conglomerate. A sandstone dominated sequence extends from 0 - 194 m in Bonaparte 1, and from 219 - 480 m in Keep River 1, where it is overlain by shale. An artesian flow of fresh water (0.33 ppt) occurred from Spirit Hills 1. Artesian conditions are likely elsewhere, especially where confined beneath the tidal flats, and the groundwater is likely to be fresh, probably extending offshore.

The aquifer is used only for pastoral purposes, and there is significant development potential.

References: Mory, A.J. and Beere, G.M., 1988. Geology of the onshore Bonaparte and Ord Basins in Western Australia: Geological Survey of Western Australia, Bulletin 134.

Lau, J.E., Commander, D.P, and Jacobson, G., 1987. Hydrogeology of Australia. Bureau of Mineral Resources, Bulletin 227.

Ningbing Group

The Ningbing Group consists mainly of reef limestones. At the Sorby Hills lead-zinc prospect there is considerable development of karst cavities, and large amounts of saline (up to 10 ppt) groundwater were pumped to assess the feasibility of dewatering, prior to mining (O'Boy and others, 2001). It is not known whether the limestone has karst development elsewhere.

Ord River Alluvium

Alluvial sediments are associated with a palaeochannel of the Ord River, which extends north eastwards from Kununurra, and with the lower Ord River beneath the Carlton-Mantinea Flats between Kununurra and Wyndham. The alluvium along the Ord River consists of gravel, overlain by sand and silt, up to 42 m thick. The alluvial gravels are high yielding. The groundwater salinity ranges from fresh, close to the Ord River, to saline on the western part of the Carlton-Mantinea Flats and towards the Keep River near Sorby Hills (O'Boy and others, 2001).

The watertable has risen below the Ord River Irrigation Area, and as a consequence, groundwater is likely to be pumped from the alluvial gravels in order to lower water levels (O'Boy and others, 2001). Groundwater from the alluvium is currently only used for Kununurra town water supply.