Abstract & Project Executive Summary


Primary Area for Consideration - Develop and evaluate innovative tools or methodologies NRCS and others can use to encourage producers to adopt improved irrigation management.


Project Duration - 3 years


Contact Information - Andy Spyrka, Ventura County Resource Conservation District, andyspyrka.vcrcd@gmail.com, 805-764-5135, PO Box 147 Somis Road Somis CA 93006


Names and Affiliates of Project Collaborators - Ben Faber, University of California Cooperative Extension, Jim Churchill, Churchill Orchard


Project Background - Although Ventura County growers express a willingness to use evapotranspiration (ET)-based irrigation scheduling technologies, they do not appear to actually use the technique. The lag in adoption appears to be related to the prevalence of microclimates in major growing areas of the County. This project seeks to expand grower use and adoption of ET-based irrigation scheduling



Expansion of Irrigation Scheduling by Reconciling Atmometer and CIMIS Station Data Within the Canyon Regions of Ventura County





 A USDA-NRCS Conservation Innovation Grant (CIG)

Project Summary

Efficient and precise irrigation management is critical if California producers are to maximize crop quality, conserve water, and protect the environment. The use of evapotranspiration (ET) estimates is a significant component of irrigation management. ET refers to the sum of water lost from the soil (evaporation) as well as that used by the crop (transpiration). While the California Irrigation Management Information System (CIMIS) network of weather stations derive daily ET values, there is a perception that CIMIS does not produce accurate ET estimates for all locations. This view is particularly prevalent in the canyons of Ventura County where weather conditions differ substantially compared to CIMIS locations. Since avocado and citrus thrive in these areas, it was concerning when it was determined that ET scheduling is not widely used.

That is, a Ventura County Resource Conservation District (RCD) review of California Department of Food and Agricultural State Water Efficiency and Enhancement Program (CDFA SWEEP) projects concluded that Ventura County growers substantially lagged their state-wide peers with respect to implementing ET-based irrigation scheduling (14% versus 44%).

RCD seeks to reverse the low implementation of ET-based irrigation scheduling within Ventura County by using simple, rugged on-site ET devices (atmometers) to determine on-site ET values. These on-site values will be compared to CIMIS values to determine local correction factors and develop refined ET maps for the canyon and valley areas. RCD will present these results at outreach events and provide workshops demonstrating how ET data, whether from CIMIS or on-site atmometers, can be used for irrigation management.

Atmometer Test/Calibration Site

Project Objectives - Objectives include expansion of ET-based irrigation scheduling within Ventura County, development of a project executive summary discussing project results and corrective factors for microclimate areas when using CIMIS data, publication of refined ET map, and on-site outreach events to demonstrate atmometer use for irrigation scheduling.


Project Methods - Atmometers measure evaporative losses directly and will be used to evaluate ET values at six cooperating growers’ properties. This information will be used to develop an ET-based irrigation schedule for each cooperator. This information will also be compared to CIMIS data to determine how the two sources compare. 


Project Geographic Area/Location - This project will determine site specific ETo values within the major avocado and citrus growing areas of Ventura County, including the Santa Clara River Valley (from the cities of Oxnard to Fillmore) and Simi Valley (from Oxnard to Moorpark).


Project Deliverables/Products - This project will develop an executive summary discussing project results, determine corrective factors for microclimate areas when using CIMIS data, publish a refined ET map, and coordinate on-site outreach events to demonstrate atmometer use for irrigation scheduling.


Description of EQIP Eligible Producer Involvement - Grower cooperators will host atmometers, provide data to RCD, incorporate irrigation scheduling, provide water use records for comparative water, energy, and fertilizer-use reductions, and host on-site demonstrations.

Atmometer Test/Calibration Site @ Hansen Farms

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