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Irrigation Calculators


In Santa Clara County, as in the rest of California, water availability and pumping costs are important considerations for the agricultural industry. Efficient irrigation methods and scheduling are the key to maximizing water and fertilizer use efficiency.

These resources will help you maximize the irrigation efficiency of your farm, orchard, or nursery. If you’re new to agriculture or want to learn more, the American Farm Bureau has resources for all ages and specialties.

Handbook for Agriculture Water-Use Efficiency


The Handbook for Agriculture Water Use Efficiency describes how to integrate into your operations the tools that are available to you as a Santa Clara County grower. These include:

  • Irrigation system fitness and distribution uniformity (DU), payback from improving DU, and evaluating pump efficiency.
  • Irrigation scheduling and evapotranspiration, maximizing the amount of marketable crop produced per unit water consumed, using the online irrigation calculator, and evaluating Available Water Capacity.
  • Soil moisture monitoring, including calculating soil moisture and describing guidelines for placing sensors.
  • Setting irrigation run times for sprinkler and drip irrigation.

California Irrigation Management Information System (CIMIS)

To help maintain the most efficient irrigation scheduling, the California Irrigation Management Information System provides current reference evapotranspiration. Valley Water maintains a CIMIS station in Gilroy that is updated daily, in partnership with Synsenta AG and the California Department of Water Resources.

View this CIMIS brochure to learn how CIMIS works, how you can access it, and how you can use it as a tool for irrigation scheduling at your farm, orchard, or nursery.

Online irrigation scheduling calculators

  • Drip Irrigation scheduling calculator for fields, vineyards, and orchards that are drip irrigated.
  • Sprinkler Irrigation scheduling calculator for sprinkler-irrigated fields and orchards.

These calculators make it easy to calculate your crop's irrigation requirements based on your local CIMIS weather station data and the percentage of your field that is shaded by the crop around high noon. Of course, it's essential to check your soil moisture to ensure that your calculated irrigation amounts are doing the job.

The calculators ask for information you may not know yet. The calculators will suggest values to plug in to get at least a provisional answer. Then, call Valley Water at (408) 630-2951 to schedule an irrigation system evaluation during one of your normally scheduled irrigations. We will develop the rest of the information so you can use the calculator for more precise estimates.

Crop water requirements

Maximize your water use by understanding estimated crop water requirements. View the estimated cumulative irrigation requirements for several crops of importance in the Llagas Valley, as well as crop-specific details. 


For more information about this program, contact Ashley Shannon at (408) 630-2951.

To learn about Valley Water’s other water conservation programs, contact the Water Conservation Hotline at (408) 630-2554 or email [email protected].