Vine Notes: North Coast vines need long-term water planning

Nearly half of California is in “exceptional drought,” according to the U.S. Drought Monitor, which has been costly to many agricultural producers throughout the state. North Coast winegrape producers have had significant reason to be concerned in the last two years, but the auspicious timing of less-frequent rainstorms are helping vineyards and wineries in Napa and Sonoma counties continue to turn water into wine.

Higher than usual temperatures and lower precipitation in the counties leaves Napa and Sonoma in “extreme” and “severe” drought conditions, as indicated below. Fortunately, winegrapes require less water than many other agricultural endeavors, and to date, production in Napa and Sonoma Counties has not been significantly impacted by the persistent drought. While rainfall in the North Coast area has been below normal, this region usually receives much more rain than other parts of California. Napa and Sonoma counties, for example, usually gets twice the rain as Paso Robles and nearly three times the rain seen in Fresno.

Napa and Sonoma counties have water challenges of their own. In the short term, they are very dependent upon local precipitation, and in the long term, both have areas of modest groundwater deficit.

Napa vineyards grow 35%

In Napa County, winegrape vineyard acreage has increased from 32,000 in 1993 to 43,500 in 2013, yet it accounts for less than a third of agricultural production acreage. The remainder acreage is primarily in cattle and rangeland. In the county, there are numerous private small reservoirs, which are used for storing water usually needed for frost protection and for irrigation at season’s end when the soil moisture in vineyards declines.

Local water agencies are increasing their treatment of wastewater and piping it to areas to recharge ground-water deficit areas, such as in Coombsville and Carneros. However, the drought has had a major impact on urban consumers in Napa County, as State Water Project deliveries have been reduced for the second year and the State Water Resources Control Board has mandated conservation in most communities. At present, recent precipitation has proved to be enough to fill public reservoirs this year.

Sonoma vine acres double

The increase in vineyard plantings in Sonoma County has increased even more, rising from 31,000 acres in 1993 to nearly 60,000 acres in 2013. Yet, winegrape vineyards only account for 7 percent of agricultural land in the county, as a majority of the land is in pasture and rangeland. The county has water storage in Lake Mendocino and Lake Sonoma that is diverted to the three major valleys and more. This indirectly benefits some agriculture users, who rely upon wells, since it helps sustain the local aquifers.

However in June 2014, curtailments were made to the Dry Creek Valley and Healdsburg areas and vineyards further north in response to the drought. Vineyard operators had to rely upon other stored water in local ponds and wells to sustain their winegrape production.

There have been no announced plans of such curtailment this year, and both reservoirs have more water stored than they did last year. The long-term challenge for Sonoma County vineyards may be in the Russian River watershed, where endangered species and increased diversions may forced more reliance on groundwater pumping for irrigation and frost protection.

Groundwater plans

In the North Coast region, with its relatively larger water supply, there still needs to be more focus on developing region-by-region groundwater sustainability plans. Although the area’s aquifers are not considered “high priority,” as determined by the California State Department of Water Resources, there nonetheless needs to be a comprehensive plan in place, else the state developed rules will take effect.

In the North Coast, this will be 2022, compared with 2020 in the high-priority areas. However, that time will come sooner than many expect, and if the lack of urgency results in not enough steps taken toward selecting agencies to develop regional plans, the state imposed rules will be forced upon North Coast growers.

“Statewide, all but the holders of the most senior water rights in California agriculture will be increasingly vulnerable to the cost of future droughts as the state’s water system is further stressed by environmental regulations, outdated infrastructure, and population growth. Future investment in higher-valued agricultural production will be limited, if more progress is not made toward improving the reliability of water availability for agricultural production.”

That is from the concluding section of the September 2012 Rabobank report “Water for California Agriculture: Tapping Out.” The severity of this drought makes the report even more relevant today. Please let me know, if you are interested in this Rabobank research report or any of the other reports about food and agriculture.

Charles Day (Charles.Day@rabobank.com) is senior vice president and area manager of the North Coast Food & Agriculture group of Rabobank, NA.