Water Management in Sonoma County Grape Production

Project Overview

Project Type: Professional + Producer
Funds awarded in 2012: $49,200.00
Projected End Date: 12/31/2012
Region: Western
State: California
Principal Investigator:
Karen Thomas
Sonoma County Winegrape Commission


  • Fruits: grapes


  • Crop Production: irrigation
  • Education and Training: demonstration, extension, farmer to farmer, workshop

    Proposal abstract:

    Despite naturally high levels of winter rainfall, water is a scarce resource for Sonoma County, and competition from various interests (agricultural, municipal, environmental) has increasingly become contentious. The use of water for frost protection in vineyards, in particular, and for seasonal irrigation has come under scrutiny by the California Water Resources Control Board (CWRCB), resulting in proposed regulations that may limit the use of water for frost protection of grapes in the Russian River watershed.

    There are over 60,000 acres of vineyards in Sonoma County. Coho salmon in the county are listed as "endangered" under the federal Endangered Species Act (ESA). Chinook salmon and steelhead also found in the county are listed as "threatened" under the ESA. The use of water to protect grapevines from spring frosts poses risks to these species due to the instantaneous demand for water during frost events, and alleged fish takes have occurred in association with frost events. Low flows during summer months, when there is no rainfall and irrigation is required, pose additional risks to salmonids.

    In order to preserve grape growing in Sonoma County and protect threatened and endangered salmonids, growers need to make efficient use of water for frost protection and for irrigation. Currently, many growers measure only ambient temperature to determine when to activate frost protection; however, knowledge of the dew point is also required to accurately determine the risk of frost damage. As a result, growers typically use an elevated temperature threshold (35-36°F, for example) to trigger frost protection, as a conservative approach to protection. Unfortunately, that approach typically leads to unneeded or premature activation of overhead sprinkler systems. We propose to conduct outreach to growers, including a spring frost workshop, and provide guidance for optimal decision-making for frost protection operation.

    Frost protection by applications of agricultural crop sprays is being suggested as alternatives to sprinkler irrigation by the CWRCB. Antibacterial sprays, often containing copper, have been shown in some crops (not grapes) to reduce the population of ice nucleating bacteria on plant surfaces, thus reducing intercellular ice formation inside the plant and subsequent tissue damage. We propose to conduct an objective evaluation of selected materials in a project producer’s vineyard that does not use overhead sprinklers for frost protection.

    Irrigation is another major use of water by the wine grape growers of the region. It is believed that growers, though intending to be good stewards, continue to irrigate prematurely each year, and irrigate in an inefficient manner. New technologies for measuring soil and plant moisture status are available to guide more efficient irrigation. We believe, from previously executed surveys and field demonstrations, that growers could collectively conserve 30% or more of the applied water and maintain economic yields, all the while improving wine quality.

    We propose to collect measurements of soil and plant moisture status at three sites throughout the county to enable grower exposure to these technologies. This will allow us to work with growers to fine-tune their irrigation based on soil and plant water status data, vine observations and overall strategies for winegrape production. The sites will be selected to represent variations of soil and climatic characteristics, as well as varieties grown. Results from the demonstrations will be communicated to growers through workshops and field days, newsletter articles and on the Commission website, www.sonomawinegrape.org.

    Sonoma County grape growers have traditionally participated in grower educational events and programs to improve production practices, and changes in practices have been documented for pesticide use, for example. Thus, improved management practices that are identified with the proposed demonstrations are likely to result in improved efficiencies in water use for both frost protection and irrigation.

    Project objectives from proposal:

    1. Frost Protection:

    1a. Explore alternative methods to overhead sprinkler frost protection: Demonstrate the efficacy, if any, of applied frost protection materials, such as antitranspirants and copper fungicides/bactericides in a Sonoma County vineyard. Spring 2012

    1b. Utilize a network of weather stations to measure temperature and dew point at key locations across the county: Real time weather data from a nearby weather station can be accessed by growers to determine when frost protection systems are needed and e-mail or text message alarms can be set to alert growers of current frost risks and to time irrigation initiation and termination. Spring 2012 and 2013.

    1c. Provide education to reduce or avoid false or early triggering of overhead sprinklers: Demonstrate the proper triggering of overhead sprinklers for frost protection to alleviate overuse during frost episodes. Provide simple-to-operate, accurate equipment to growers to use for triggering of overhead sprinkler frost protection. Spring 2012 and 2013.

    2. Irrigation Management:

    2a. Avoid deep percolation of irrigation water which has the potential of groundwater contamination: Demonstrate the use of soil moisture monitoring equipment and how it may be used in three Sonoma County Vineyards to determine proper volume of irrigation to avoid excessively deep water movement. Summer 2011and 2012

    2b. Avoid excessive use of irrigation water by adjusting intervals based on need: Demonstrate the use of soil moisture monitoring equipment in three Sonoma County vineyards and how it may be used to determine proper intervals between irrigation applications. August 2011 and 2012

    2c. Determine proper, site-specific irrigation regimes: Demonstrate the different irrigation practices appropriate for representative soil types and conditions in three Sonoma County vineyards. August 2011 and 2012

    2d. Avoid seasonal premature applications of irrigation to vineyards in Sonoma County by taking advantage of soil moisture storage from winter precipitation. Demonstrate the use of shoot tip observations to trigger the onset of irrigation.

    2e. Demonstrate the benefits and limitations of plant water status measurements under several climatic and soil conditions in three Sonoma County vineyards.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.