Written by David Doll (UCCE Merced County) and Allan Fulton (UCCE Tehama County) This past week I presented on our preliminary findings of the water production function trials underway across the state. Highlights included the release of some newer crop coefficients that were determined using eddy-covariance stations placed in the North and South, discussion on water needs, and the impact of water stress on crop growth. Of most interest was the crop coefficients, which were higher than what most operations use, and led to the questions of the need for that much water. Crop coefficients (Kc) are derived to estimate ET for various crops as they develop over the course of a season.  Kc’s are developed under conditions where soil moisture is not limited and the crop is not stressed at all.    So, they represent maximum ET or water use.  . In the case of almonds, there have been several recent efforts to determine these values (see below). Various methods have been used ranging from simpler soil-water balance to more advanced biometeorologic eddy-covariance measurements. All of these have led to significantly higher calculated Kc’s and crop ET, with one set suggesting that around 60″ of water was needed in Bakersfield conditions. It is important to keep in mind that ET does not equal irrigation need.  The two will be more similar in almond growing areas with lower rainfall and more different in higher rainfall areas.  Water holding capacity of orchard soils and root depth will also influence the relationship between ET and irrigation need.   Even increases in production do not necessarily correspond with higher ET and more irrigation. There is increasing evidence that when given the conditions, “luxury consumption” of water will occur. In other words, the water demand is present, but crop load does not increase. This highlights the value of