Agricultural clientele utilize Extension information to inform irrigation management decisions, potentially improving water use efficiency and protecting California's water resources.

The Issue

For farmers to grow high-yielding and good quality crops and be good stewards of our finite water resources, they need to know how much water is used by their crop and how much to refill the soil with irrigation. Weather conditions and the crop's life stage determine the water use, also known as crop evapotranspiration (ET). When farmers have accurate crop ET information available, they can more closely apply the appropriate amount of water at the right time and grow more and better quality food and fiber with each unit of water.

How UC Delivers

Since 1995, UC ANR has collaborated with the Department of Water Resources (DWR) to deliver weekly crop ET estimates to growers for the major crops grown in California. These ET estimates integrate real-time, on-the-ground weather measurements taken by DWR and decades of research by UC ANR on crop water use. These reports provide growers with representative estimates of crop ET each week and a running total of crop water use as each crop develops. The weekly rates of ET can be related to the water application rate of an irrigation system to help determine how frequently to irrigate and how long to run a system. Comparing cumulative ET early in the season to the available soil moisture can help decide when to apply the first irrigation of the season. At the end of the season, a comparison of the seasonal ET to total applied irrigation water provides a yardstick to assess irrigation efficiency. Beginning in 2000, methods of delivering these weekly reports expanded to include email and blogs. In 2015, these reports expanded to UC ANR offices throughout the Central Valley to serve more than 1,200 clientele throughout California.

The Impact

In 2019, a one-time survey was sent to about 1,200 clientele throughout California, including growers, agricultural land managers, and crop advisors to understand how the weekly ET reports were being used, quantify the impact of use of the emails, and assess the needs of irrigation education. The survey findings indicated that 70% of clientele use these weekly ET reports in irrigation management decisions. Of that 70%, 75% use the information to inform how long to irrigate, 73% how frequently to irrigate, 53% when to begin the irrigation season, and 39% when to end the irrigation season.

Research has shown that scheduling irrigation based on ET can improve plant health and yields, translating to more crop per drop. Previous UC ANR research has demonstrated that California growers save approximately $64.7 million per year by using CIMIS weather station data. In this way, UC ANR contributes to improved water use efficiency, demonstrating UC ANR's commitment to the public value of protecting California's natural resources.