Launch Slideshow

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Demanding a better way

Demanding a better way

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    To sustain San Diego's continual growth, the city must import 90% of its potale water. Photos: CDM

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    Factors impact forecastingThrough advanced water demand forecasting, communities are looking beyond per capita figures in an effort to yield precise, meaningful data for water managers. Source: COM

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    San Diego's Miramar water treatment plant is one facility that figures into the department's strategic plans for water supply, urban water management plan, raw and treated water master plan, and planning for improvements to the water distribution system.

Factors affect average water use

Empirical research has identified several factors that affect the average rate of residential and nonresidential urban water use. Some change on a monthly basis, while others change over longer periods. These factors include:

  • Air temperature: Determines growing seasons, evapotranspiration rates, and cooling needs. As temperature increases, average water use tends to increase.
  • Precipitation: Reduces irrigation water requirements; as precipitation increases, average water use tends to decrease.
  • Cooling degree days: Measured as the number of degrees by which the average temperature exceeds 65° F. Reflects cooling water requirements. As the number of cooling degree days increase, average water use tends to increase.
  • Household income: Determines the consumer's ability to pay for water and measures the standard of living. As median household income increases, average water use per household tends to increase.
  • Persons per household: Determines the frequency and intensity of use of water-using fixtures within the home. As household size increases, the average water use per household tends to increase.
  • Housing density: Reflects the standard of living and amount of land available for irrigation. Can be measured as the number of housing units per acre, or as the average lot size. As the number of housing units per acre increases, the average water use per household tends to decrease. Conversely, as the average lot size increases, average water use tends to increase.
  • Price of water and sewer service: The price of water and wastewater service influences the amount of water the consumer is willing to purchase. As the marginal price increases, average water use tends to decrease.
  • Industrial productivity: As commercial and industrial processes become more efficient, average water use tends to decrease.
  • Water use efficiency: As consumers select more efficient water-using appliances and behaviors, average water use tends to decrease.
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