Bulletin 160-93, The California Water Plan Update, October 1994

Definition of Terms

• Applied water: The amount of water from any source needed to meet the demand of the user. It is the quantity of water delivered to any of the following locations:
  • the intake to a city water system or factory.
  • the farm headgate.
  • a marsh or wetland, either directly or by incidental drainage flows; this is water for wildlife areas.
  • For existing instream use, applied water demand is the portion of the stream flow dedicated to instream use or reserved under the federal or State Wild and Scenic Rivers acts or the flow needed to meet salinity standards in the Sacramento-San Joaquin Delta under SWRCB standards.
• Evapotranspiration: The quantity of water transpired (given off) and evaporated from plant tissues and surrounding soil surfaces. Quantitatively, it is expressed in terms of volume of water per unit acre of depth of water during a specified period of time. Abbreviation: ET.
• Evapotranspiration of applied water: The portion of the total evapotranspiration which is provided by irrigation. Abbreviation: ETAW.
• Irrecoverable losses: The water lost to a salt sink or water lost by evaporation or evapotranspiration from conveyance facilities or drainage canals.
• Net water demand: The amount of water needed in a water service area to meet all the water service requirements. It is the sum of evapotranspiration of applied water in an area, the irrecoverable losses from the distribution system, and the outflow leaving the service area, including treated municipal outflow.
• Depletion: The water consumed within a service area and no longer available as a source of water supply. For agriculture and wetlands it is ETAW plus irrecoverable losses. For urban areas it is the exterior ETAW, sewage effluent that flows to a salt sink, and incidental ET losses. For instream needs it is the dedicated flow that proceeds to a salt sink.
• Average year demand: The demand for water under average weather conditions for a defined level of development.
• Drought year demand: The demand for water during a drought period for a defined level of development. It is the sum of average year demand and water needed for any additional irrigation of farms and landscapes due to the lack of precipitation or increase in evapotranspiration during drought.
• Normalized demand: The result of adjusting actual water use in a given year to account for unusual events such as dry weather conditions, government interventions for agriculture, rationing programs, etc.

Back to Executive Summary, Chapter 3, Water Demands

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