Last Updated: February 2026
California Groundwater Depletion Statistics 2026
California depends on groundwater for 40% of its water supply in normal years and up to 60% during drought. Decades of overdraft have depleted aquifers across the state, causing land subsidence and threatening long-term water security. This page presents current statistics on California's groundwater crisis.
📋 In This Guide
Table of Contents
- Groundwater Overview
- Overdraft by Basin
- Land Subsidence Data
- Water Level Trends
- SGMA Compliance Status
- Southern California Data
California Groundwater Overview
| Statistic | Value | Source |
|---|---|---|
| Total groundwater basins | 515 | CA DWR |
| Critically overdrafted basins | 21 | CA DWR |
| High/medium priority basins | 94 | CA DWR |
| Groundwater wells in California | ~1.5 million | USGS |
| Annual groundwater use | 15-20 million AF | CA DWR |
| Groundwater % of CA supply (normal year) | 40% | PPIC |
| Groundwater % of CA supply (drought) | 60% | PPIC |
Critically Overdrafted Basins
California has designated 21 groundwater basins as "critically overdrafted":
| Basin | Region | Overdraft (AF/year) | SGMA Deadline |
|---|---|---|---|
| San Joaquin Valley (Kern County) | Central Valley | ~500,000 | 2040 |
| Tulare Lake | Central Valley | ~400,000 | 2040 |
| Cuyama Valley | Central Coast | ~28,000 | 2040 |
| Paso Robles | Central Coast | ~13,000 | 2040 |
| Borrego Valley | San Diego | ~5,700 | 2040 |
| Indian Wells Valley | Kern/Inyo | ~7,200 | 2040 |
Land Subsidence Data
Excessive groundwater pumping causes the land to sink (subside), damaging infrastructure:
| Area | Total Subsidence (Historical) | Recent Rate |
|---|---|---|
| San Joaquin Valley (max) | 28+ feet | 1-2 ft/year in worst areas |
| Santa Clara Valley | 13 feet | Stabilized (managed recharge) |
| Sacramento Valley | 3-6 feet | 0.2-0.5 ft/year |
| Coachella Valley | 3 feet | 0.1-0.2 ft/year |
| Borrego Valley | 2 feet | 0.1-0.3 ft/year |
Water Level Trends
Groundwater level changes from 2000 to 2025:
| Region | Average Level Change | Trend |
|---|---|---|
| Central Valley (overall) | -50 to -100 feet | Declining |
| Southern San Joaquin | -100 to -200 feet | Severely declining |
| San Diego County | -10 to -30 feet | Moderately declining |
| Riverside County | -20 to -50 feet | Declining |
| Coastal basins (managed) | Stable to +10 feet | Stable/improving |
SGMA Compliance Status (2026)
The Sustainable Groundwater Management Act (SGMA) requires sustainability by 2040/2042:
| Status | Number of GSAs | Percentage |
|---|---|---|
| GSP Approved | 78 | 62% |
| GSP Under Review | 32 | 25% |
| GSP Inadequate (revision needed) | 12 | 10% |
| State Intervention | 4 | 3% |
Southern California Groundwater Data
| Basin | Priority Level | Status | Key Issues |
|---|---|---|---|
| San Diego Formation | Medium | Stable | Limited storage, salinity |
| San Pasqual Valley | Medium | GSP in progress | Agricultural use |
| Borrego Valley | Critical | Overdrafted | 60% reduction needed |
| Temecula Valley | Medium | Stable | Urbanization pressure |
| Coachella Valley | High | Managed | Recharge programs active |
Implications for Well Owners
- Deeper wells needed: Average new well depth has increased 50-100 feet in many areas
- Higher drilling costs: Deeper wells = higher costs ($50-$100+ per additional foot)
- Pumping restrictions: Some areas now limit new wells or pumping volumes
- Metering requirements: SGMA may require well metering in critical basins
- Fees possible: Groundwater sustainability agencies can charge pumping fees
Key Takeaways
- 2 million acre-feet annual overdraft statewide
- 21 basins classified as critically overdrafted
- 28 feet maximum historical subsidence (San Joaquin Valley)
- $2 billion estimated annual economic cost
- 2040 deadline for critical basins to achieve sustainability
- Borrego Valley is the only critically overdrafted basin in San Diego County
📚 Cite This Page
Southern California Well Service. "California Groundwater Depletion Statistics 2026." SCWS Resources, February 2026.
https://scwellservice.com/blog/california-groundwater-depletion-statistics.html
Sources
- California Department of Water Resources (DWR)
- U.S. Geological Survey (USGS)
- NASA GRACE Satellite Data
- Public Policy Institute of California (PPIC)
- State Water Resources Control Board
- Groundwater Sustainability Agencies (GSAs)
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