End of Season Northern Sacramento Valley ET Report- November 17


Estimated Crop Evapotranspiration (ETc) for November 10-16, 2023

This report covers the CIMIS stations in Tehama County (Gerber South), Butte County (Biggs and Durham) and Colusa County (Williams). More information on using ET Reports is available here.

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  • *Accumulations started on March 1st, 2023, or on the approximate leafout date for a specific orchard crop.
  • Estimates are for orchard floor conditions where vegetation is managed by some combination of strip applications of herbicides, frequent mowing or tillage, and by mid and late season shading and water stress. Weekly estimates of soil moisture loss can be as much as 25% higher in orchards where cover crops are planted and managed more intensively for maximum growth.

Since the growing season for the principal summer crops is coming to an end, this will be the last weekly issue of Evapotranspiration (ET) data for the 2023 irrigation season. This was the 48th season of providing ET information for the North Valley. The ET data will be made available next spring at the start of the 2024 irrigation season.


This information is provided as a joint effort by the California Department of Water Resources’ Northern Region Office, the University of California Cooperative Extension in Glenn and Yolo Counties (a.k.a. Glenn and Yolo County Farm Advisor’s office), and this newspaper. It is intended as an aid to irrigators to help determine when to irrigate and also how much water to apply.


The ET data, which appears weekly in this newspaper during the irrigation season, is a measure of the amount of water that is lost from the soil root zone due to crop use and soil surface evaporation. These are typically the most significant losses of soil moisture during the growing season. To gain the maximum value from this information you need to look for it each week during the irrigation season and compare it to how much irrigation water is applied with your irrigation system or how much rainfall is received.


If this is the first time that you have observed this information, you may want to note that these reports will be resumed approximately March 2023, depending on the spring weather conditions. In the meantime, you may want to make note of the season totals and compare them to your district water bills or estimates of groundwater pumped per acre. The comparison might provoke some interesting questions.


Information on how to use these weekly reports can be found at sacvalleyorchards.com/et-reports. Each weekly soil moisture loss report is posted at this site including a two-page article with examples of how to use the report. A request for a hard copy of this article can be made at University of California Cooperative Extension in Glenn Co. Farm Advisors office at (530) 865-1153 or by calling the California Department of Water Resources, Northern Region Office at (530) 317-8555.


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