A new supply well was drilled at Cook on the trans- Australia railway line, to replace an existing one which was producing excess suspended solids, thus clogging the filters of the township's desalination plant. The new well used a wirewound screen instead of slotted casing; it was constructed with 150 mm steel casing driven 1.5 metres into the aquifer to stabilize the over-lying claystone, which was at one stage believed to have been responsible for the trouble with the number 2 well. The problems associated with the number 2 well were caused either by inadequate well construction, allowing claystone to enter the well under the influence of pumping, or by bacteriological action. Although drawdown measurements could not be made in the new well, a brief aquifer test was carried out at a rate of 280 kl/day using the number 2 well for observations. This showed the aquifer to have a high transmissivitv (915 m /day/m) and small storage coefficient (1.43 x 10 ) . The well should be capable of long term pumping at a rate of 100 kl/day, appropriate to the demands of the desalination plant. Drawdown in the production well will increase only very slowly over prolonged periods of pumping, however it should be tested with drawdown measurements when the pump has been installed with the recommended plastic pipe.