Irrigation in the Pacific Northwest

Drip Design for Landscapes

The estimated water use form calculates a rough estimate of the water use by landscapes receiving drip irrigation. Use the second form to estimate how many emitters should be used for each plant. Learn more about the units used on this page.

Estimated Water Use Per Plant

Individual Plant Area:
Plant Type:
Estimated Water Use Per Plant:


Minimum Number of Emitters Per Plant for the above water use per plant if the irrigation can run constantly (24 hrs a day, 7 days a week).
Emitter Flow Rate:
Number of Emitters Per Plant:
This is a minimum. Rounding up, or putting more emitters per plant means that the system doesn't have to run all the time.



The Equations

These are the formulas used by the calculators to determine the estimated water use and number of emitters per plant.


Water Use Per Plant


= Water use per plant (gpd)

= Individual plant area (sq. ft)

= Plant type. An arbitrary value used to account for different plant types. (see table)

= Climate type. An arbitrary value used to account for different climate types. (see table)


Number of Emitters Per Plant


= Number of Emitters Per Plant

= Water use per plant from Estimated Water Use per Plant calculator

= Emitter flow rate (gpd)


Plant and Climate Type Values

Plant Type () Value Climate Type () Value
Trees 1.1 Cool Humid 0.13
Shrubs 0.9 Cool Dry 0.17
Ground Cover 1 Warm Humid 0.18
Mixed 1.1 Warm Dry 0.22
Turf Grass 0.8 Hot Humid 0.25
Hot Dry 0.33


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