Sonoma County Supervisors are expected to declare a "drought emergency" Tuesday, a move designed to make the county eligible for possible state and federal aid.

"There's nothing we couldn't do for ourselves outside of that, to be sure that those funds are accessible," Chairman David Rabbitt said Friday.

The county already was part of a disaster declaration issued in January by the U.S. Department of Agriculture, making agricultural businesses eligible for federal assistance.

Supervisors say the county declaration is necessary in anticipation of state and federal legislation that could reimburse local governments for both short-term emergency measures, such as compensating farmers for crop losses and beefing up staffing to meet increased fire danger, and long-term conservation, such as distributing efficient water fixtures and encouraging small-scale, seasonal storage options.

"The proclamation is all about protecting our funding requests," said Supervisor Mike McGuire. His north county district has been hit hard by the drought because it is not served by the large Lake Sonoma reservoir and relies solely on the smaller Lake Mendocino and depleted upper reaches of the Russian River.

The board's action will not have any immediate effect on the operations of the Sonoma County Water Agency, which provides drinking water for about 600,000 customers from Windsor south, including parts of Marin County.

Agricultural interests have been hard hit in the drought, which saw the smallest rainfall total in recorded history, with less than 9 inches in Santa Rosa. Sonoma County Agricultural Commissioner Tony Linegar is estimating near complete crop losses on pastures and fields producing hay, oats and other grains. As of Jan. 31, he was estimating economic losses of at least $6.2 million.

Sonoma County's declaration comes more than a month after a flurry of disaster declarations by other governments and agencies, including the USDA. Gov. Jerry Brown issued a statewide declaration on Jan. 17, calling on water users to cut consumption by 20 percent voluntarily.

Mendocino County was the first county in the region to act, declaring an emergency Jan. 8, in large part to get access to state and federal assistance for the beleaguered towns reliant on drinking water from Lake Mendocino, which is down to 41 percent of its capacity. Even worse hit was the town of Willits, which relies on two small reservoirs that were nearly dry, leaving the city with less than 100 days of reserves.

The Sonoma County cities that use Lake Mendocino water have also enacted more stringent measures than those that rely on Lake Sonoma, which is still at about 68 percent capacity, well more than a year's supply. Cloverdale and Healdsburg have both imposed mandatory water conservation, including banning most outdoor uses.

Cities relying on Lake Sonoma water have asked residents to conserve voluntarily and the Water Agency, which sells water to the cities on a wholesale basis, has asked for at least 20 percent voluntary conservation.

Before they consider the drought declaration Tuesday, supervisors will hear an extensive report from county agencies, detailing their efforts to respond to the drought. The Agricultural Commissioner, for example, is preparing to implement a water trucking program to serve ranchers, similar to one used in the drought of 1976-77, the last severe dry spell in the region.

The Transportation and Public Works Department, meanwhile, has stopped washing vehicles and switched to a more water-efficient truck-mounted system for washing culverts and storm drains. It has also contracted with a private water hauler to back up small water systems it runs in the Freestone, Jenner and Salmon Creek areas.

The supervisors, who also serve as directors of the Water Agency, warn that mandatory conservation measures may be necessary even in areas served by Lake Sonoma if there is not significant rain in the rest of the spring.

"The next month, month-and-a-half will be very telling," West County Supervisor Efren Carrillo said, "allowing us to determine whether to take additional conservation measures."

(You can reach Staff Writer Sean Scully at 521-5313 or sean.scully@pressdemocrat.com. On Twitter @BeerCountry.)