Sonoma County Well Statistics 2026: 48 Facts & Data
Sonoma County Well Overview
Sonoma County, California's premier wine region alongside Napa, has an extensive groundwater infrastructure. The county overlies multiple groundwater basins regulated under SGMA, including the Santa Rosa Plain (High Priority), Sonoma Valley, and Petaluma Valley basins.
Source: Sonoma County Permit Sonoma, DWR Bulletin 118
Well Population by Type
| Well Type | Number | % |
|---|---|---|
| Domestic/Residential | 18,200 | 74.3% |
| Agricultural/Vineyard | 4,800 | 19.6% |
| Monitoring | 720 | 2.9% |
| Public Supply | 480 | 2.0% |
| Industrial | 300 | 1.2% |
Key Sonoma County Facts
- ~600,000 people served by Sonoma County Water Agency wholesale system
- 150,000+ residents rely on private wells
- 60,000+ acres of vineyard (Wine Country)
- 3 SGMA-regulated basins: Santa Rosa Plain, Sonoma Valley, Petaluma Valley
- 1,768 square miles county area
- 488,000 county population (2026)
- DWR Bulletin 118-4 provides comprehensive groundwater evaluation
- Sonoma County Water Agency major regional water manager
Wells by Community
Top Areas by Well Count
| Area | Wells | Avg Depth |
|---|---|---|
| Santa Rosa Rural | 4,850 | 245 ft |
| Petaluma Area | 3,200 | 225 ft |
| Sonoma Valley | 2,980 | 285 ft |
| Sebastopol | 2,450 | 195 ft |
| Healdsburg/Alexander Valley | 2,180 | 265 ft |
| Windsor | 1,850 | 235 ft |
| Cloverdale | 1,420 | 215 ft |
| Dry Creek Valley | 1,280 | 295 ft |
| Occidental/Coast | 1,150 | 345 ft |
| Guerneville/Russian River | 980 | 165 ft |
Groundwater Basin Data
Source: California DWR, Sonoma County GSAs
Groundwater Basins
| Basin | Priority | Area | Status |
|---|---|---|---|
| Santa Rosa Plain | High | ~80 sq mi | GSP Implemented |
| Sonoma Valley | Medium | ~45 sq mi | GSP Implemented |
| Petaluma Valley | Medium | ~30 sq mi | GSP Implemented |
Groundwater Level Trends
| Basin/Area | 5-Year Change | Status |
|---|---|---|
| Santa Rosa Plain (shallow) | -4.5 ft | Declining |
| Santa Rosa Plain (deep) | -8.2 ft | Declining |
| Sonoma Valley | -6.8 ft | Declining portions |
| Petaluma Valley | -3.2 ft | Slight decline |
| Alexander Valley | -2.1 ft | Stable |
DWR Bulletin 118-4 Studies
California DWR has published extensive groundwater evaluations for Sonoma County:
- Volume 1 (1975): Geologic and Hydrologic Data
- Volume 2 (1982): Santa Rosa Plain
- Volume 3 (1982): Petaluma Valley
- Volume 4 (1982): Sonoma Valley
- Volume 5 (1983): Alexander Valley and Healdsburg Area
Permit Statistics
Permit Types (2026)
| Type | Count | % |
|---|---|---|
| New Domestic | 142 | 60.7% |
| New Agricultural | 52 | 22.2% |
| Replacement | 26 | 11.1% |
| Deepening | 10 | 4.3% |
| Monitoring | 4 | 1.7% |
10-Year Permit Trend
| Year | Permits | Change |
|---|---|---|
| 2026 | 198 | +5% |
| 2026 | 256 | +29% |
| 2026 | 268 | +5% |
| 2026 | 212 | -21% |
| 2026 | 218 | +3% |
| 2026 | 234 | +7.3% |
Permit Requirements
- Permit fee: $1,580 domestic (2026)
- Processing time: 10-21 business days
- Well spacing: Varies by basin regulation
- SGMA compliance: May require GSA notification in priority basins
Drilling Costs (2026)
Costs by Area
| Area | Low | Avg | High |
|---|---|---|---|
| Petaluma Valley | $26,000 | $38,000 | $62,000 |
| Santa Rosa Plain | $28,000 | $42,000 | $68,000 |
| Sonoma Valley | $32,000 | $48,000 | $78,000 |
| Sebastopol | $25,000 | $36,000 | $58,000 |
| Alexander Valley | $30,000 | $44,000 | $72,000 |
| Coastal (Occidental, Bodega) | $42,000 | $58,000 | $95,000 |
Cost per Foot
- Alluvium: $40-55/ft
- Volcanic (Sonoma Volcanics): $55-75/ft
- Franciscan (Coast): $65-90/ft
Water Quality
Common Issues
| Issue | % Affected |
|---|---|
| Hard water | 32% |
| Iron/Manganese | 18% |
| Nitrates | 6% |
| Arsenic | 4% |
| Boron | 5% |
We service all major pump brands including Franklin Electric, Grundfos, Goulds (Xylem), and Sta-Rite (Pentair). Our trucks carry common parts and components for same-day repairs.
Frequently Asked Questions
How many wells are in Sonoma County?
Sonoma County has approximately 24,500 registered wells, including 18,200 domestic and 4,800 agricultural wells.
What groundwater basins are in Sonoma County?
Three SGMA-regulated basins: Santa Rosa Plain (High Priority), Sonoma Valley (Medium), and Petaluma Valley (Medium).
Are groundwater levels declining?
Yes, portions of Santa Rosa Plain and Sonoma Valley show declining groundwater levels. GSAs are implementing sustainability plans.
What is the average well depth?
Domestic wells average 265 feet; coastal areas may require 300-500 feet.
How much does a well cost?
Average cost is $45,500 for a complete system (2026), ranging from $25,000 to $95,000.
Need Well Information?
For Sonoma County well services, contact Permit Sonoma at (707) 565-1900.
For San Diego/Riverside: (760) 440-8520
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