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Water Demand - Forecasts

A number of external factors influence water demand including:

  • population size and growth;
  • average household size;
  • rainfall patterns;
  • incidence of very hot days;
  • business activity; and
  • the availability of alternative water sources such as garden bores and rainwater tanks.

Water Forever is basing water demand on the major factor of population growth.

Residential demand is calculated by assuming that customers manage to reduce Perth household water use to 100 kilolitres of water a year, a target set in the State Water Plan 2007. This is a decrease in current household water use, which has averaged 107 kilolitres a year over the past 6 years. Of this water, about half is used outside the home.

Other demands include water supplied by the IWSS water grid for use by business, industry, services such as hospitals and schools, fire fighting and water losses through leakage.

This demand has averaged 47 kilolitres a year over the past 6 years. Combined with household water use, water consumption per person averages 153 kilolitres a year.

These demand assumptions reflect recent use and highlight the significant gains made in water use efficiency over the past 10 years. This represents a reduction in overall water demand of approximately 17% since the peak demand of 185 kilolitres a year in 2000/01.

 

These forecasts demonstrate a commitment to meet the target to reduce residential water use to 100 kilolitres a person for people in Perth, as outlined in the State Water Plan 2007. This saving will require continued and additional investment in water use efficiency initiatives.

They do not include additional water supply to meet Perth and Mandurah industrial demand, which is predominantly met through self-supply groundwater, water recycling and trading. 

Note that these demand forecasts could be significantly impacted by the factors outlined above. Further analysis will be conducted to investigate the sensitivity of these projections to impacts of household size, hot days, urban density and other considerations.