South-west Western Australia (SWWA) is experiencing a long-term drying trend linked to climate change which is likely to persist. The water management response contains useful lessons for a nation likely to experience similar conditions in the future.
The average flow rate into Perth’s dams has declined steeply: the 2006-2010 average was 57.7 GL/year compared to an average of 177 GL/year for the period 1975-2010.
The management response for public water supply has included developing more climate independent water sources. In 2005-6, half the public water supply was from surface reservoirs, and half from groundwater. By 2010-11, the effective supply from surface reservoirs had dropped to 22%; desalination supplied 20% and groundwater supplied the balance. As we write, at the beginning of 2013, approximately 50% of water is derived from desalination. At the same time, efforts are being made to reduce consumer demand.
Desalinated water is delivered at approximately $2.20/kL, compared to 20c/kL for water from surface reservoirs.
Findings relevant to Australian water policy include the need to: utilise all water sources from a portfolio of supply options; use fit-for-purpose water for appropriately planned and designed infrastructure and property developments; protect the ecosystems and biodiversity; encourage demand reduction and lower levels of outdoor use; inform the public and train workforces to enable adaptation. The needs of more vulnerable consumers for a secure low-cost water supply must be maintained. Water management should be integrated into land planning decisions. Under a changing climate, thresholds can be assigned to trigger management responses, infrastructure investment and/or shifts in supply sources.
This Guidance Brief deals with the challenge of managing the urban water supply under climate change. The example location is south-west Western Australia (SWWA), which is experiencing a long-term drying trend linked to climate change that will likely persist. The water management response contains useful lessons for a nation likely to experience similar conditions in the future.