In 1958, under the authority of Sonoma Water's enabling legislation, the formation of nine geographical zones, each encompassing a major watershed, was proposed as a means of financing the construction and maintenance of flood protection works within Sonoma County.
Over the succeeding several years, Zones 1A, 2A, 3A, 5A, 7A and 8A were officially formed. Zones 1A, 2A, and 3A have Zone Advisory Committees that annually prioritize and approve capital improvement projects for their respective zones.
In November 1986 and again in 1996, the electorate of Zones 1A and 2A authorized the levying of benefit assessments within these two zones for 10 years to augment funds received from general property taxes. Since 1986 these revenues have supplemented the property taxes received by Zones 1A and 2A.
The officially formed zones have financed the construction of flood protection and drainage facilities, the maintenance of natural waterways, the preparation of master drainage plans for areas subject to flooding, and erosion and sediment control activities. The zones have also financed the flood protection operation and maintenance activities of Sonoma Water.
See maps for each of the nine zones below: