The Ukiah Daily Journal reports that the county's Board of Supervisors on Tuesday voted unanimously to make the declaration, citing an "imminent threat of disaster" from drought conditions.
The state Department of Water Resources said Mendocino is the first to request state drought assistance.
Officials hope the declaration will result in state funds and assistance in developing a drought plan.
Gov. Jerry Brown has convened a task force to help decide if a statewide drought emergency is warranted.
State water managers say they will be able to deliver just 5 percent of the water sought by municipal agencies and nearly a million acres of farmland.
(AP) - The latest figures show Californians' water use is still on the rise since the state lifted mandatory conservation for the drought.
(AP) - President Barack Obama has signed a bill authorizing water projects across the country, including $170 million to address lead in the drinking water in Flint, Michigan, and $558 million to provide relief to drought-stricken California.
Rivers in the Sacramento area were reaching levels not seen in a decade on Thursday night.
California state agencies have released a long-term plan for water conservation. The proposal makes permanent some emergency water conservation measures already in place to deal with the state’s drought.
California regulators hear from residents and farmers concerned about a plan to provide more water for threatened fish in the San Joaquin River and its tributaries.