Irrigation in the Pacific Northwest

Irrigatable Area As Limited By Water Supply

This calculates the land area that can be irrigated with a given flow of water. The minimum system capacity (supply) is the available water from the supply. The water needs is the peak crop water need during a specific time period. Go here, or here for estimates for Washington. The available hours of operation per day is measured as the available hours for irrigation on a worst case day. The system efficiency is based on the irrigation efficiency and distribution uniformity. Learn more about the units used on this page.

Minimum System Capacity (Supply):
Operation Hours Per Day:
System Efficiency:
Irrigatable Area:



The Equation

This calulator uses this formula to determine the Irrigatable area.


= Irrigatable Area (sq. ft)

= Minimum system capacity, or supply (gpm)

= Water needs (in/day)

= Operation hours per day (hrs)

= System Efficiency (as a decimal)






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