Anderson Valley Vineyards: Navarro Water, Fish Habitat, Ridge Overlap and Zoning

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Anderson Valley is a narrow coastal valley in western Mendocino County, drained by the Navarro River system toward the Pacific and running from above Boonville past Philo and Navarro. Owning vineyard land here is shaped less by valley-floor zoning debates and more by water: small surface diversions in a salmon and steelhead watershed, a shallow alluvial groundwater basin, and a federal appellation that shares an edge with the Mendocino Ridge AVA. The appellation name on a parcel does not tell you whether the land can be planted, irrigated or built on; that takes its own review.

Anderson Valley at a glance

Where the appellation runs

The federal rule at 27 CFR 9.86 describes the boundary as a series of straight lines and creek courses rather than contour lines. It starts where Bailey Gulch meets the South Branch North Fork Navarro River, runs southeast to a 2,015-foot hilltop, then southwest and northwest to section lines, follows Greenwood Creek for a stretch near Cold Springs Road, and closes back to the starting point by way of Benchmark 1057. Because the lines are straight segments between survey points, a ranch near the edge can straddle the line, so map each block rather than relying on the mailing address.

The TTB list of established AVAs places Anderson Valley inside the larger Mendocino and North Coast appellations and notes a partial overlap with Mendocino Ridge. The Mendocino Ridge rule at 27 CFR 9.158, added in 1997, covers only land at or above the 1,200-foot elevation line, and its boundary description runs along the Anderson Valley line and the Navarro River to the ocean. For a hillside parcel above the valley, that means some vine blocks could qualify for both names and others for only one; elevation survey work matters.

For context on how this appellation fits the rest of the state, see our California wine regions guide and the Mendocino County vineyards page.

Water: a Navarro River watershed, not the Russian River

The single biggest difference from inland Mendocino vineyards is the watershed. Anderson Valley drains to the Navarro, not to the Russian River. The State Water Board’s Russian River frost protection regulation, adopted September 20, 2011, applies to diversions from the Russian River stream system in Sonoma and Mendocino Counties from March 15 through May 15. Its program page does not name the Navarro or Anderson Valley, so do not assume a Russian River Water Demand Management Program governs a Boonville or Philo vineyard; confirm with the Division of Water Rights how frost water is handled on the specific parcel.

What the State Water Board does say about the Navarro is telling. In an October 1, 2024 program presentation, staff described the watershed as roughly 315 square miles, beginning where Rancheria and Anderson Creeks join just south of Philo. It listed 254 water rights in the watershed, dominated by many small agricultural, commercial and residential diversions, and named the Navarro as one of three pilot watersheds (with Butte Creek and the Napa River) for the Board’s supply-and-demand modeling. Rights holders file annual reports that include month-by-month diversion and use. For a buyer, the practical point is that a pond, a creek pump or an offstream reservoir is only as good as its documented right and its reporting record.

Fish habitat and the sediment and temperature TMDLs

The same presentation identifies the Navarro as critical habitat for coho salmon and steelhead. The North Coast Regional Water Quality Control Board’s Navarro River TMDL page records sediment and temperature TMDLs established by USEPA in December 2000, with the sediment TMDL folded into a Regional Board resolution in November 2004. New planting, road work and creek crossings on sloped ground are where these listings show up in practice: erosion control, riparian setbacks and agency consultation can add time to a project. Our environmental constraints guide covers how listed species and stream rules affect vineyard plans.

Groundwater in the valley floor

DWR’s Bulletin 118 description of the Anderson Valley groundwater basin (basin 1-19) (a 2004 DWR entry hosted by the Anderson Valley Community Services District) puts the basin at about 4,970 acres in the southwestern part of the valley. Recent alluvium, stream channel deposits and terrace deposits carry most of the water; the surrounding Franciscan bedrock is described as essentially non-water-bearing. The basin is generally unconfined, with a localized pressure area around Boonville, and reported well yields range from 5 to 300 gallons per minute. Two takeaways: hillside ranches outside the alluvial basin may depend on fractured bedrock wells with very different yields, and wells close to the river may be treated as connected to surface flow. Check the current DWR basin prioritization for the basin’s SGMA status rather than relying on an older listing. See also vineyard water rights and vineyard ponds and reservoirs.

Zoning, permits and Williamson Act contracts

Anderson Valley is unincorporated, so land use is set by Mendocino County’s inland zoning and General Plan, with the Coastal Zone rules applying only where a parcel reaches the coastal boundary. Agricultural and rangeland zones generally allow farming, but a winery, tasting room, events, a second home or a farm-labor unit are separate questions, and each needs its own county review alongside state and federal permits. California ABC licensing and TTB wine premises approval are distinct from county land-use approval; see winery license transfer and how to start a winery.

Many larger Mendocino ranches sit under Williamson Act contracts. The Department of Conservation’s Williamson Act Q&A explains that standard contracts run on rolling 10-year terms, renew each year unless nonrenewal starts, and bind every later buyer of the land. A Farmland Security Zone contract runs on a 20-year rolling term. Cancellation carries a 12.5% fee and only the landowner can start it. Ask for the recorded contract and the county’s current preserve rules before you plan any homesite split or non-farm use; our Williamson Act guide goes further.

Fire, smoke and access

Most of the hills around the valley are wildland. CAL FIRE’s Fire Hazard Severity Zone maps classify land as Moderate, High or Very High hazard; State Responsibility Area maps took effect April 1, 2024, and Local Responsibility Area maps were released in early 2025. Look up the parcel, then price insurance early. Long private roads, single-lane bridges and gated easements are common off Highway 128, and they affect both fire response and harvest logistics. Read our Philo private roads and site access guide, wildfire smoke taint and vineyard and winery insurance.

A due diligence list for an Anderson Valley vineyard

• Map every vine block against the 27 CFR 9.86 line and, for upland blocks, the 1,200-foot Mendocino Ridge contour.
• Pull the State Water Board eWRIMS records for every pond, creek pump and spring: right type, season, amount and recent monthly reports.
• Ask the Division of Water Rights how frost and irrigation diversions on this parcel are regulated; do not assume the Russian River frost program applies.
• Separate wells in the alluvial basin from bedrock wells; get pump tests timed for late summer.
• Review erosion, road and stream-crossing history in light of the Navarro sediment and temperature TMDLs and coho and steelhead habitat.
• Confirm the inland or coastal zoning district and every county permit behind existing winery, tasting or residential uses.
• Obtain any recorded Williamson Act or Farmland Security Zone contract and the county’s current preserve rules.
• Check the CAL FIRE hazard zone, defensible space status and road access for fire apparatus.
• Review grape purchase contracts, vine age, rootstock and virus history.
• Work through the full vineyard due diligence checklist.

Questions people ask

Sources & notes

1. eCFR: 27 CFR 9.86 Anderson Valley
2. eCFR: 27 CFR 9.158 Mendocino Ridge
3. TTB: Established American Viticultural Areas
4. State Water Board: Russian River frost protection regulation
5. State Water Board, Division of Water Rights: Navarro River watershed supply and demand presentation, Oct. 1, 2024
6. North Coast Regional Water Quality Control Board: Navarro River sediment and temperature TMDLs
7. DWR Bulletin 118: Anderson Valley groundwater basin 1-19 (2004 entry, hosted by Anderson Valley CSD)
8. DWR: Basin prioritization
9. California Department of Conservation: Williamson Act questions and answers
10. CAL FIRE Office of the State Fire Marshal: Fire Hazard Severity Zones

General information, not legal or tax advice. Last reviewed November 2026 by Matthew Martinez.

Related: Mendocino County vineyards · Boonville real estate guide · Philo real estate guide · Boonville rural water and wastewater · Red Hills Lake County vineyards · Russian River Valley vineyards · Vineyard due diligence · Vineyard water rights · All vineyard and winery guides