The water supply for Sydney, which is the largest city in Australia, has been affected by variable climate patterns which include long periods of drought. Water resource needs for the future will be significantly affected by climate change and population growth. A ‘Water for Life’ equation has been adopted as a multi-faceted approach to achieving future, sustainable water security. The four parts of the equation are dams, recycling, water efficiency and desalination. Significant achievements have been made over the last 10 years which have allowed us to bolster the demand/supply balance by 50%. In the future, a portfolio approach will be used to select schemes for water supply security. Major factors considered will include construction and operational cost, volume of water saved or produced, public health and environmental risk, customer and community acceptance and political willpower.