Australian Natural Resources Atlas

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Water resources - Overview - New South Wales

Location map of North Coast Fractured Rocks

Groundwater Management Unit: North Coast Fractured Rocks

Introduction

Delineation of this area as a GMU arose from a NSW state-wide review of all aquifers as part of the NSW Water Reform process. The objective of the review was to identify aquifers which there was some risk that abstraction of groundwater could not be maintained in a sustainable way. The risk assessment was based on a set of weighted criteria which included current usage patterns, size, land use, apparent threats to groundwater quality and dependent ecosystems. Aquifers not included in existing GMUs, but which were deemed to be at high risk and for which there were data indicating a history of groundwater abstraction, have been incorporated as GMUs for the purpose of the NLWRA. In some cases the rate of groundwater abstraction is as yet only very small, and in all cases the degree of management effort applied is at a relatively low level pending implementation of appropriate procedures. In some cases these procedures will include the establishment of a local groundwater management committee with which DLWC will cooperate in the development of a groundwater management policy appropriate for that area. The North Coast fractured rock GMU is delineated by the outcrop area of the basalt of the Mt Warning Complex, with the exception of the Alstonville Plateau which has been declared a GMU in its own right. The area ocupies most of the far north-east corner of the State north of about Ballina, except for the extreme north-east corner occupied by the sedimentary rocks of the Clarence-Morton Basin. There are nu merous reentrants in the boundary, where the underlying Jurassic sediments are exposed in lower topographical areas. The basalt occurs in a series of sub-horizontal flows, with a total thicknes of over 100m, usually separated by weathered surfaces and/or paleosol layers. The old surfaces, and some of the more fractured flows, constitue quite good aquifers, and usefull supplies can be obtained from well sited bores over much of the area. Recharge is mainly by infiltration of rainfall via the fracture network. Discharge of groundwater as springs is a characteristic of areas such as this, and these springs can provide a substantial part of the base flow of streams draining the area. Consequently, maintnenance of groundwater dependent e2cosystems will be an important factor in the management of groundwater in this GMU.

Vital Statistics:

Area: 2,040 Km2
Total water allocated: no data
Total water consumed: 2,400 ML/yr
Average salinity: 150 mg/l
Sustainable yield: 80,000 ML/yr
Depth to top of aquifier: 20 m

Further Information

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