This Briefing Paper is an update on the 2004 Briefing Paper The Future of Water Supply. The 2004 Paper highlighted the fact that at the time, Sydney was using 106 percent of the annual sustainable yield of its water supplies. This Paper is divided into two parts. Part One updates the development of Government policy in relation to Sydney water supply. Part Two is divided into three sections. Section one provides an overview of desalination plants and technology from around the world, including case studies. Section two reviews water recycling, whilst section three compares and contrasts the two water cycle approaches.

On 19th October 2004, Meeting the challenges - Securing Sydney's water future was released by the NSW Government. The plan - covering the next 25 years – outlines the Government’s actions to secure the future water supply for Sydney. Actions proposed included: accessing water stored deep in dams; transferring water from the Shoalhaven River during high flow periods; large scale recycling programs for new land release areas; and investigating desalination.

In mid July 2005 the then Premier Bob Carr announced plans for a desalination plant at Kurnell. Whilst this plant was originally proposed as drought proofing measure, the new Premier Morris Iemma has stated that the plant will be built ‘drought or no drought’. The proposed desalination plant attracted considerable debate. One of the major criticisms of the Metropolitan Water Plan was that it did not provide for the reuse of treated waste water into potable supplies. In response, the Government argued that there was no public support for this option, and that it was more expensive than desalination.

Worldwide over 23 million m3/day of desalinated water is produced. The majority of production is in the Middle East and North Africa. Whilst there are numerous techniques to produce desalinated water, reverse osmosis has the largest installed capacity. Reverse osmosis has wider applications than just removing salt from seawater for potable use. A wastewater treatment process including micro-filtration, reverse osmosis and ultraviolet disinfection can produce high quality water. Several countries now use this process to augment their water supplies, and case studies of both desalination and waste water reuse are presented.