California water planners and the environmental community would like to meet increasing urban water demand by efficiency improvements in ag irrigation. A 75 percent to 80 percent irrigation efficiency has been considered good to excellent in the past. However, Kern water districts and growers have said for more than 20 years that they are operating at a higher efficiency due to increasing water costs and continued low commodity prices.

New innovations in microelectronics now provide cost-effective opportunities for growers to monitor soil moisture to document and, in some cases, improve the precision of irrigation to increase crop yield. Starting in the winter of 2001 Kern UCCE worked together with the local Resource Conservation District Irrigation Mobile lab to instrument grower’s fields with neutron probe access tubes, tensiometers, electrical resistance blocks (Watermarks) and a continuously recording data logger (Hanson AM400) with a visual display that does not require downloading to a computer.

Growers were faxed one page weekly irrigation scheduling recommendations also containing a seasonal summary of CIMIS ET estimates, soil moisture and applied water history to optimize crop performance and irrigation water use efficiency (WUE). Additional fields on the Westside of Kern County were added to this program in 2002 as part of a two-year CalFed Ag Water Use Efficiency project. Additional grower fields (from 8 to 18) have been instrumented every year since 2003 with a low-cost logger/sensor combination for a total of 138 fields covering 11,491 acres farmed by 27 different producers in 14 different crops, 11 soil textures and 9 different irrigation system types have been set up by the end of 2005.

Visual display

Loggers provide growers with a visual display of soil water content change at the side of the field without having to download data to a computer. The cost of this logger/sensor system is about $800 per field.

The average measured water use efficiency for all CalFed study fields was 95 percent. Significant water savings were realized in furrow irrigated cotton and some Buttonwillow pistachios. Yields in almonds, cotton and wine grapes were improved. Data generated during this project has provided the field evidence to substantiate the claim that irrigated agriculture in Kern County is operating at 90 to 95 percent water use efficiency. This is an unparalleled level of irrigation efficiency for regional production agriculture that is much higher than previously thought possible.

The take home message is that there may not be the assumed “conservation savings” that planners hope to squeeze out of California ag.

Presentations on this project, water policy, water conservation in the urban sector and some of the technology available for managing water efficiently will be made at the upcoming California Irrigation Institute (CII) annual meeting: “Water Conservation: Truth and Consequences” at the Radisson Hotel in Sacramento.

Jan. 26 discussion

The conference opens on Jan. 26, with a panel discussion focusing on “Water Conservation Myths and Realities”. This panel represents environmental, urban, ag and policy perspectives presented by Peter Gleick, president of the Pacific Institute; Jerry Johns, deputy director of the California Department of Water Resources; Tim Quinn, vice president of the Metropolitan Water District of Southern California; Van Tenney, retired general manager of the Glenn-Colusa Irrigation District; and Wayne White, field supervisor for the U.S. Fish & Wildlife Service.

David Guy, executive director of the Northern California Water Association, will moderate the panel. It concludes Friday, Jan. 27, with a presentation by Pulitzer Prize winner Tom Philp, the Sacramento Bee reporter who won the journalism award for a series of articles about the potential removal of Hetch Hetchy dam to restore this once spectacular river valley.

CII is California's oldest running independent forum (since 1962) on water and irrigation, and has always been distinguished by a practical and cooperative approach among industry, university and agency personnel dedicated to meeting the real water needs of the state in all economic sectors. CII’s core objectives are to advance knowledge relating to irrigation, improve irrigation practices, increase the public’s appreciation for the importance of water to California's economy; strengthen cooperation among those interested in irrigation and water management issues, and to heighten professional and social interaction between the irrigation community and water policy leaders.

Further details about the conference, including online registration, are available on the institute’s Web site, www.caii.org. Information may also be obtained by phone at (916) 366-9376.