Irrigation in the Pacific Northwest

Select a Calculator

These irrigation calculators will help compute your irrigation needs based on your growing practices, types of soil, and vegetation.



Irrigation Management Calculators

  • Irrigation Frequency: maximum interval allowed between irrigations. This is dependent on soil type, root zone depth, and the water use rate of the crop.
  • Set Times: set time required to fulfill a given water application, irrigation area, and flow rate.
  • Water Depth: Depth of water applied to a specified area over the specified time span based on the given flow rate.
  • Water Application Rate: Application rate using the flow rate on an area.



Center Pivot


  • Drip Design for Landscapes: Determine how much water to apply to individual plants with drip emitters.
  • Garden Hose Flow Rate Calculate the flow rate and application time for a garden hose, based on hose size and supply pressure.
  • Lawn Water Management Find the application depth and operation time for a specific grass type, precipitation rate, and daily water use. Also provides suggested application depths and operation times for multiple water periods.
  • Tree Water Management Find a watering period and water quantity for a tree type, tree spread diameter, and daily water use. The results give a suggested water management schedule for watering periods and a corresponding water quantity.

General Design Calculators

Water Measurement Calculators

  • Cipolletti (Trapezoidal) Weir: Flow rate for a Cipolletti weir. The weir opening has a flat bottom and sides that have a particular slope.
  • 90° Triangular Notch Weir: Flow rate of a 90° triangular notch weir. The opening to this weir is a 90 degree triangular notch.
  • Parshall Flume: Flow rate for a Parshall Flume. It can be identified by both a section that has a contraction in the width of the flume as well as a dip in the elevation of the bottom of the flume.
  • Rectangular Contracted Weir: Flow rate for a rectangular contracted weir. A rectangular contracted weir has a rectangular opening where the sides are straight up and down.
  • Rectangular Submerged Orifices: Flow rate of water through a rectangular submerged orifice. A submerged orifice is an underwater hole that water goes through. In this case the hole has a rectangular shape.
  • Trapezoidal Flume: Flow rate for a trapezoidal flume. A trapezoidal flume has a flat bottom with sloped sides that contract in the center.

Chemigation Calculators


A staff gauge measures water levels



WSU Prosser - IAREC, 24106 N Bunn Rd, Prosser WA 99350-8694, 509-786-2226,