The Carnarvon Artesian Basin Rehabilitation Project

The Carnarvon Artesian Basin covers about 25,000 square kilometres along the Gascoyne coast. Apart from the Gascoyne River in Carnarvon, the basin provides the only reliable water source for local industry and coastal settlements.

Prior to 2000, approximately 160 artesian bores were drilled into the basin - the majority before 1960 as part of oil exploration. The construction techniques and the highly corrosive nature of the water have caused most bores either:

• to collapse - resulting in large sub-surface water losses to geological formations (from which they cannot be recovered); or
• to produce significant uncontrolled flows at the surface.

A three-year $3.5million project to rehabilitate uncontrolled artesian flows was completed in 2003.

The project was proposed as a joint initiative of the Commonwealth Government, the Gascoyne Murchison Strategy, the Water and Rivers Commission and participating pastoralists.

The objectives were to:

• reduce the number of uncontrolled bores and bore drains
• increase pressure in the artesian basin
• reduce water wastage
• improve grazing management
• improve weed and feral animal control.

Stage 1 was completed in 2003 after spending approx 3.5 million.

Results

The 1st phase of the project has resulted in the drilling of 14 new artesian bores and one rehabilitated bore constructed to industry best practice standards. This has enabled pastoral properties to develop plans based on secure water sources, including new investment in total grazing management infrastructure and diversified industries, for example, horticulture and aquaculture.

Fifty-seven uncontrolled bores were decommissioned, representing water savings of over eight gigalitres a year at the surface, with an estimated 35 gigalitres a year saved from previous sub-surface loss.

A pressure rise is already evident in some locations on the aquifer, possibly up to 40kpa in some areas. In addition, 88km of bore drain have been removed, allowing pastoralists to improve stock and feral goat management as well as to control weeds.

Stage 2 of the CABRP is currently underway, with the selection of bores to decommission and re-drill currently being identified. We anticipate that during stage two, the current 28 bores still free-flowing will all be decommissioned and approximately 10 bores re-drilled. We expect drilling to begin in the first half of 2007, with the decommissioning following soon after.

Stage 2 will also result in an Aquifer Model being completed for the CAB. The model will be used for management purposes along with completion of a groundwater management plan as part of Stage 2.