SGMA groundwater basin priority in California, by county and ZIP
California's Sustainable Groundwater Management Act (SGMA) ranks every groundwater basin. Of the state's 515 basins and subbasins, 46 are high priority and 48 medium priority, the ones required to form a groundwater sustainability agency and adopt a plan, and 21 are critically overdrafted. If you own or are buying California land that relies on a well, the basin under it decides which local groundwater agency and plan apply. Look up a ZIP code below, or find your county in the table.
Look up a ZIP code
ZIP areas are Census ZIP Code Tabulation Areas; the share is of the ZIP's area, not a parcel check. 1,518 California ZIPs overlap at least one mapped basin.
Key findings
94 of California's 515 groundwater basins and subbasins are high or medium priority under SGMA (46 high, 48 medium), the ones required to form a groundwater sustainability agency and adopt a plan; 21 are critically overdrafted.
DWR ranks basins by the relative importance of groundwater; priority is not an assessment of any well or parcel. SGMA 2019 Basin Prioritization (final table dated 2022-04-21).
Data: SGMA 2019 prioritization. Link to this finding
Sutter County has the largest share of its area in high- or medium-priority basins: 95.8%.
DWR ranks basins by the relative importance of groundwater; priority is not an assessment of any well or parcel. SGMA 2019 Basin Prioritization (final table dated 2022-04-21).
Data: SGMA 2019 prioritization. Link to this finding
2 groundwater basins are on State Water Board probation under SGMA (Tulare Lake and Tule); 4 other critically overdrafted San Joaquin Valley subbasins the Board reviewed were returned to DWR oversight without probation.
State Water Resources Control Board basin decisions, accessed 2026-11-04 (Water Code §10735.2).
Data: as of November 2026. Link to this finding
Source: California Department of Water Resources, SGMA Basin Prioritization and Bulletin 118 basin boundaries. Computed from our dataset “Groundwater basin priority (SGMA) by county” (version 2026-11-04); download the CSV. Free to reuse under CC BY 4.0 with a link to this page. Findings update when the data does.
What basin priority means for a property owner
DWR's explanation of the rankings, in its own words:
- “Although SGMA applies to all basins in California, only high- and medium-priority basins are required to form a groundwater sustainability agency (GSA) and adopt a groundwater sustainability plan (GSP) or submit an alternative to a GSP. Low- and very low-priority basins may adopt these plans but are not required to.”
- “SGMA does not treat low-priority basins differently than very low-priority basins. SGMA does not treat high-priority basins differently than medium-priority basins.”
- The rankings “provide an indicator of the overall relative importance of groundwater … The prioritization does not provide an assessment on local groundwater management practices or basin sustainability as defined in SGMA.”
- “Under SGMA, adjudicated portions of basins are exempt from developing a groundwater sustainability plan and forming a groundwater sustainability agency.”
What priority does not tell you
Priority is a basin-wide ranking. It is not a finding about any well, parcel, water level or water quality. For a well on a property, look at its depth and the county's well records, dry-well reports and water-quality results, and ask the local GSA what its plan requires.
What the law requires, and by when
The Sustainable Groundwater Management Act is Part 2.74 of the California Water Code. Its stated intent begins: “(a) To provide for the sustainable management of groundwater basins. (b) To enhance local management of groundwater …” (§10720.1). A basin is managed sustainably when groundwater is used “in a manner that can be maintained during the planning and implementation horizon without causing undesirable results” (§10721(v)). The six undesirable results, in the statute's words (§10721(x)):
- “Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon.”
- “Significant and unreasonable reduction of groundwater storage.”
- “Significant and unreasonable seawater intrusion.”
- “Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies.”
- “Significant and unreasonable land subsidence that substantially interferes with surface land uses.”
- “Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water.”
- Plans: by January 31, 2020 for critically overdrafted high- and medium-priority basins, and by January 31, 2022 for the other high- and medium-priority basins (§10720.7).
- Sustainability: each plan sets “interim milestones in increments of five years, to achieve the sustainability goal in the basin within 20 years of the implementation of the plan” (§10727.2(b)(1)), so about 2040 for critically overdrafted basins and about 2042 for the rest. Those years are derived; DWR may extend the timeframe by up to five years, twice, for good cause.
- Household wells: a “de minimis extractor” is “a person who extracts, for domestic purposes, two acre-feet or less per year” (§10721(e)). A groundwater sustainability agency may not charge one a §10730 fee “unless the agency has regulated the users pursuant to this part” (§10730(a)). Extraction fees under §10730.2 have no such carve-out, and an agency may ask the county to collect its fees “in the same manner as ordinary municipal ad valorem taxes” (§10730(d)(1)), so a groundwater fee can appear on the property tax bill.
Basin priority by county
Basins overlapping each county by priority, and the share of the county's area that lies in high- or medium-priority basins and in critically overdrafted basins. Sort by any column or type a county.
Showing 58 of 58 counties.
| County | ||||||
|---|---|---|---|---|---|---|
| San Bernardino | 90 | 2 | 2 | 1 | 0.5% | 0.3% |
| Riverside | 43 | 2 | 6 | 0 | 12.3% | 0% |
| Inyo | 39 | 1 | 0 | 1 | 1% | 1% |
| San Diego | 37 | 1 | 3 | 1 | 3.6% | 2.3% |
| San Luis Obispo | 27 | 4 | 1 | 4 | 23.4% | 23% |
| Kern | 26 | 5 | 1 | 5 | 41.8% | 39.7% |
| Lassen | 24 | 0 | 1 | 0 | 2.2% | 0% |
| Ventura | 24 | 10 | 1 | 3 | 21.7% | 13% |
| Mendocino | 22 | 0 | 1 | 0 | 1.7% | 0% |
| Los Angeles | 19 | 1 | 2 | 0 | 3.8% | 0% |
| Sonoma | 17 | 1 | 2 | 0 | 16.8% | 0% |
| Humboldt | 16 | 0 | 1 | 0 | 3.1% | 0% |
| Imperial | 16 | 0 | 1 | 0 | 0.1% | 0% |
| Modoc | 16 | 0 | 2 | 0 | 3.3% | 0% |
| Monterey | 14 | 5 | 4 | 3 | 26.4% | 5.5% |
| Shasta | 14 | 0 | 2 | 0 | 6.5% | 0% |
| Plumas | 13 | 0 | 1 | 0 | 4.1% | 0% |
| San Benito | 13 | 2 | 1 | 2 | 15.3% | 1% |
| Lake | 12 | 0 | 1 | 0 | 2.9% | 0% |
| Siskiyou | 12 | 0 | 4 | 0 | 10.1% | 0% |
| Mono | 11 | 0 | 0 | 0 | 0% | 0% |
| Colusa | 10 | 2 | 2 | 0 | 59.5% | 0% |
| Contra Costa | 10 | 0 | 5 | 0 | 25.4% | 0% |
| Glenn | 10 | 3 | 1 | 0 | 46.7% | 0% |
| San Mateo | 10 | 1 | 0 | 0 | 0% | 0% |
| Santa Barbara | 9 | 2 | 3 | 1 | 22.2% | 6.1% |
| Tehama | 9 | 3 | 3 | 0 | 29.1% | 0% |
| San Joaquin | 8 | 4 | 4 | 2 | 93.8% | 68.3% |
| Fresno | 7 | 5 | 1 | 5 | 42.5% | 41.3% |
| Kings | 7 | 6 | 0 | 6 | 78.1% | 78.1% |
| Sacramento | 7 | 4 | 3 | 1 | 94.6% | 0% |
| San Francisco | 7 | 0 | 0 | 0 | 0% | 0% |
| Santa Cruz | 7 | 2 | 1 | 2 | 35.2% | 27.4% |
| Sutter | 7 | 4 | 3 | 0 | 95.8% | 0% |
| Alameda | 6 | 0 | 4 | 0 | 40.6% | 0% |
| Butte | 6 | 3 | 3 | 0 | 41% | 0% |
| Napa | 6 | 2 | 0 | 0 | 9.3% | 0% |
| Yolo | 6 | 4 | 2 | 0 | 82.9% | 0% |
| Madera | 5 | 5 | 0 | 5 | 38% | 38% |
| Marin | 5 | 0 | 1 | 0 | 0.1% | 0% |
| Merced | 5 | 4 | 0 | 3 | 79.3% | 68.5% |
| Placer | 5 | 1 | 0 | 0 | 13.9% | 0% |
| Santa Clara | 5 | 2 | 2 | 0 | 28.9% | 0% |
| Stanislaus | 5 | 5 | 0 | 3 | 72.5% | 25.5% |
| Trinity | 5 | 0 | 0 | 0 | 0% | 0% |
| Tulare | 5 | 4 | 0 | 4 | 31.7% | 31.7% |
| Yuba | 5 | 2 | 3 | 0 | 40.9% | 0% |
| Solano | 4 | 1 | 1 | 0 | 49.6% | 0% |
| Del Norte | 3 | 0 | 0 | 0 | 0% | 0% |
| Orange | 3 | 0 | 1 | 0 | 43.6% | 0% |
| Sierra | 3 | 0 | 1 | 0 | 7.9% | 0% |
| Calaveras | 2 | 1 | 1 | 1 | 7.5% | 7.5% |
| El Dorado | 2 | 0 | 1 | 0 | 1.3% | 0% |
| Mariposa | 2 | 1 | 0 | 1 | 0.5% | 0.5% |
| Alpine | 1 | 0 | 0 | 0 | 0% | 0% |
| Amador | 1 | 0 | 1 | 0 | 13.5% | 0% |
| Nevada | 1 | 0 | 0 | 0 | 0% | 0% |
| Tuolumne | 1 | 1 | 0 | 0 | 0.1% | 0% |
Counts are basins whose boundary overlaps the county (slivers under 0.1 km² dropped), so a basin that spans counties counts in each. Area shares are of the whole county area. Download: groundwater-basin-priority-by-county.csv.
The 21 critically overdrafted basins
DWR quotes SGMA: “A basin is subject to critical overdraft when continuation of present water management practices would probably result in significant adverse overdraft-related environmental, social, or economic impacts.”
| Basin | Priority | Counties | Area (sq mi) | Plan status |
|---|---|---|---|---|
| Borrego Valley – Borrego Springs (7-024.01) | High | San Diego | 98 | no GSP in DWR GSP-areas layer |
| Corralitos – Pajaro Valley (3-002.01) | High | Monterey, San Benito, Santa Cruz | 117.3 | no GSP in DWR GSP-areas layer |
| Cuyama Valley (3-013) | High | Kern, San Luis Obispo, Santa Barbara, Ventura | 377.7 | GSP Under Periodic Review |
| Indian Wells Valley (6-054) | High | Inyo, Kern, San Bernardino | 596.4 | GSP Under Periodic Review |
| Pleasant Valley (4-006) | High | Ventura | 31 | GSP Under Periodic Review |
| Salinas Valley – 180/400 Foot Aquifer (3-004.01) | High | Monterey | 140.2 | GSP Under Periodic Review |
| Salinas Valley – Paso Robles Area (3-004.06) | High | Monterey, San Luis Obispo | 681.5 | GSP Under Periodic Review |
| San Joaquin Valley – Chowchilla (5-022.05) | High | Madera, Merced | 227.5 | GSP Inadequate; State Water Board returned basin to DWR 2025-06-03 |
| San Joaquin Valley – Delta-Mendota (5-022.07) | High | Fresno, Madera, Merced, San Benito, San Joaquin, Stanislaus | 1,195.3 | GSP Inadequate; State Water Board returned basin to DWR 2026-04-07 |
| San Joaquin Valley – Eastern San Joaquin (5-022.01) | High | Calaveras, Sacramento, San Joaquin, Stanislaus | 1,195 | GSP Under Periodic Review |
| San Joaquin Valley – Kaweah (5-022.11) | High | Kings, Tulare | 689.1 | GSP Inadequate; State Water Board returned basin to DWR 2025-12-03 |
| San Joaquin Valley – Kern County (5-022.14) | High | Kern, Kings, San Luis Obispo | 2,784.9 | GSP Inadequate; State Water Board returned basin to DWR 2025-09-17 |
| San Joaquin Valley – Kings (5-022.08) | High | Fresno, Kings, Madera, Tulare | 1,533.3 | GSP Under Periodic Review |
| San Joaquin Valley – Madera (5-022.06) | High | Fresno, Madera | 543.2 | GSP Under Periodic Review |
| San Joaquin Valley – Merced (5-022.04) | High | Madera, Mariposa, Merced, Stanislaus | 801.5 | GSP Incomplete |
| San Joaquin Valley – Tulare Lake (5-022.12) | High | Fresno, Kern, Kings, Tulare | 837.3 | GSP inadequate; on State Water Board probation since 2024-04-16 |
| San Joaquin Valley – Tule (5-022.13) | High | Kern, Kings, Tulare | 746.3 | GSP inadequate; on State Water Board probation since 2024-09-17 |
| San Joaquin Valley – Westside (5-022.09) | High | Fresno, Kings | 971.6 | GSP Under Periodic Review |
| Santa Clara River Valley – Oxnard (4-004.02) | High | Ventura | 90.4 | GSP Under Periodic Review |
| Santa Cruz Mid-County (3-001) | High | Santa Cruz | 56.7 | GSP Approved |
| Los Osos Valley – Los Osos Area (3-008.01) | Very Low | San Luis Obispo | 6.6 | adjudicated (all or part, per DWR table) |
Basins on State Water Board probation
When a basin's plan is found inadequate, the State Water Board “after notice and a public hearing, may designate a high- or medium-priority basin as a probationary basin” (Water Code §10735.2). Of the basins the Board has taken up, 2 are on probation, 4 were returned to DWR oversight and 1 is under evaluation. What probation means for pumping and reporting in a basin is set out on the Board's page for that basin.
| Subbasin | Status | Board decision |
|---|---|---|
| Tulare Lake (5-022.12) | On probation | April 16, 2024 |
| Tule (5-022.13) | On probation | September 17, 2024 |
| Pleasant Valley (5-022.10) | Under evaluation | — |
| Chowchilla (5-022.05) | Returned to DWR | June 3, 2025 |
| Kern County (5-022.14) | Returned to DWR | September 17, 2025 |
| Kaweah (5-022.11) | Returned to DWR | December 3, 2025 |
| Delta-Mendota (5-022.07) | Returned to DWR | April 7, 2026 |
Source: State Water Resources Control Board, SGMA groundwater basins and the Board's basin pages and press releases, accessed November 4, 2026. “Returned to DWR” means the Board handed the basin back to DWR's oversight without probation; its priority is unchanged. Check the Board's page for the current status.
Other high- and medium-priority basins
26 high-priority basins
| Basin | Priority | Counties | Area (sq mi) | Plan status |
|---|---|---|---|---|
| Carpinteria (3-018) | High | Santa Barbara, Ventura | 12.5 | GSP Approved |
| Gilroy-Hollister Valley – Llagas Area (3-003.01) | High | Santa Clara | 74 | no GSP in DWR GSP-areas layer |
| Las Posas Valley (4-008) | High | Ventura | 69.7 | GSP Under Periodic Review |
| Napa-Sonoma Valley – Napa Valley (2-002.01) | High | Napa | 71.8 | GSP Approved |
| Napa-Sonoma Valley – Sonoma Valley (2-002.02) | High | Napa, Sonoma | 70.1 | GSP Approved |
| Ojai Valley (4-002) | High | Ventura | 9.2 | GSP Approved |
| Sacramento Valley – Antelope (5-021.54) | High | Tehama | 29.8 | GSP Approved |
| Sacramento Valley – Colusa (5-021.52) | High | Butte, Colusa, Glenn, Sutter, Yolo | 1,131 | GSP Approved |
| Sacramento Valley – Corning (5-021.51) | High | Butte, Glenn, Tehama | 324 | GSP Approved |
| Sacramento Valley – North American (5-021.64) | High | Placer, Sacramento, Sutter, Yolo, Yuba | 534.8 | GSP Approved |
| Sacramento Valley – South American (5-021.65) | High | Sacramento, San Joaquin, Yolo | 388.1 | GSP Approved |
| Sacramento Valley – South Yuba (5-021.61) | High | Sutter, Yuba | 170.3 | GSP Under Periodic Review |
| Sacramento Valley – Vina (5-021.57) | High | Butte, Glenn, Tehama | 288.9 | GSP Approved |
| Sacramento Valley – Yolo (5-021.67) | High | Colusa, Sacramento, Solano, Sutter, Yolo | 844.8 | GSP Approved |
| Salinas Valley – East Side Aquifer (3-004.02) | High | Monterey | 89.8 | GSP Approved |
| Salinas Valley – Langley Area (3-004.09) | High | Monterey | 27.5 | GSP Approved |
| San Jacinto (8-005) | High | Riverside | 247.7 | adjudicated (all or part, per DWR table); GSP Approved |
| San Joaquin Valley – Modesto (5-022.02) | High | San Joaquin, Stanislaus, Tuolumne | 383.2 | GSP Approved |
| San Joaquin Valley – Turlock (5-022.03) | High | Merced, Stanislaus | 544 | GSP Approved |
| San Luis Obispo Valley (3-009) | High | San Luis Obispo | 19.9 | GSP Approved |
| Santa Clara River Valley – Fillmore (4-004.05) | High | Ventura | 35.3 | GSP Approved |
| Santa Clara River Valley – Mound (4-004.03) | High | Ventura | 21.7 | GSP Approved |
| Santa Clara River Valley – Piru (4-004.06) | High | Ventura | 17 | GSP Approved |
| Santa Clara River Valley – Santa Clara River Valley East (4-004.07) | High | Los Angeles, Ventura | 105.8 | GSP Approved |
| Santa Clara Valley – Santa Clara (2-009.02) | High | San Mateo, Santa Clara | 296.2 | no GSP in DWR GSP-areas layer |
| Upper Santa Ana Valley – Yucaipa (8-002.07) | High | Riverside, San Bernardino | 34.7 | GSP Approved |
48 medium-priority basins
| Basin | Priority | Counties | Area (sq mi) | Plan status |
|---|---|---|---|---|
| Big Valley (5-004) | Medium | Lassen, Modoc | 143.9 | GSP Approved |
| Big Valley (5-015) | Medium | Lake | 37.9 | GSP Approved |
| Butte Valley (1-003) | Medium | Siskiyou | 124.6 | GSP Approved |
| Carmel Valley (3-007) | Medium | Monterey | 6.8 | no GSP in DWR GSP-areas layer |
| Coachella Valley – Indio (7-021.01) | Medium | Imperial, Riverside, San Diego | 464.3 | no GSP in DWR GSP-areas layer |
| Coachella Valley – Mission Creek (7-021.02) | Medium | Riverside, San Bernardino | 75.9 | no GSP in DWR GSP-areas layer |
| Coachella Valley – San Gorgonio Pass (7-021.04) | Medium | Riverside | 60.2 | GSP Approved |
| Coastal Plain Of Los Angeles – Santa Monica (4-011.01) | Medium | Los Angeles | 49.7 | GSP Approved |
| Coastal Plain Of Orange County (8-001) | Medium | Los Angeles, Orange, Riverside, San Bernardino | 350.4 | no GSP in DWR GSP-areas layer |
| Eel River Valley (1-010) | Medium | Humboldt | 114 | GSP Approved |
| Elsinore – Elsinore Valley (8-004.01) | Medium | Riverside | 36.9 | GSP Approved |
| Gilroy-Hollister Valley – North San Benito (3-003.05) | Medium | San Benito, Santa Clara | 204.7 | GSP Approved |
| Klamath River Valley – Tulelake (1-002.01) | Medium | Modoc, Siskiyou | 172.7 | GSP Approved |
| Livermore Valley (2-010) | Medium | Alameda, Contra Costa | 108.7 | no GSP in DWR GSP-areas layer |
| Montecito (3-049) | Medium | Santa Barbara | 9.6 | GSP Approved |
| Petaluma Valley (2-001) | Medium | Marin, Sonoma | 72.9 | GSP Approved |
| Redding Area – Anderson (5-006.03) | Medium | Shasta, Tehama | 154.2 | GSP Approved |
| Redding Area – Enterprise (5-006.04) | Medium | Shasta | 95.8 | GSP Approved |
| Sacramento Valley – Butte (5-021.70) | Medium | Butte, Colusa, Glenn, Sutter | 414.8 | GSP Approved |
| Sacramento Valley – Los Molinos (5-021.56) | Medium | Tehama | 155.3 | GSP Approved |
| Sacramento Valley – North Yuba (5-021.60) | Medium | Butte, Sutter, Yuba | 95.1 | GSP Under Periodic Review |
| Sacramento Valley – Red Bluff (5-021.50) | Medium | Tehama | 424.7 | GSP Approved |
| Sacramento Valley – Solano (5-021.66) | Medium | Contra Costa, Sacramento, San Joaquin, Solano, Yolo | 554.2 | GSP Approved |
| Sacramento Valley – Sutter (5-021.62) | Medium | Colusa, Sutter, Yolo, Yuba | 446.6 | GSP Approved |
| Sacramento Valley – Wyandotte Creek (5-021.69) | Medium | Butte, Yuba | 92.8 | GSP Approved |
| Salinas Valley – Corral De Tierra Area (3-004.10) | Medium | Monterey | 48.2 | GSP Approved |
| Salinas Valley – Forebay Aquifer (3-004.04) | Medium | Monterey | 147 | GSP Approved |
| Salinas Valley – Upper Valley Aquifer (3-004.05) | Medium | Monterey, San Luis Obispo | 371.9 | GSP Approved |
| San Antonio Creek Valley (3-014) | Medium | Santa Barbara | 105.4 | GSP Approved |
| San Joaquin Valley – Cosumnes (5-022.16) | Medium | Amador, Calaveras, Sacramento, San Joaquin | 328.6 | GSP Approved |
| San Joaquin Valley – East Contra Costa (5-022.19) | Medium | Contra Costa, Sacramento, San Joaquin | 168.1 | GSP Approved |
| San Joaquin Valley – Pleasant Valley (5-022.10) | Medium | Fresno | 75.3 | GSP Inadequate |
| San Joaquin Valley – Tracy (5-022.15) | Medium | Alameda, Contra Costa, San Joaquin | 372.5 | GSP Approved |
| San Joaquin Valley – White Wolf (5-022.18) | Medium | Kern | 168 | GSP Approved |
| San Luis Rey Valley – Upper San Luis Rey Valley (9-007.01) | Medium | San Diego | 30.1 | GSP Approved |
| San Pasqual Valley (9-010) | Medium | San Diego | 5.5 | GSP Approved |
| Santa Clara Valley – East Bay Plain (2-009.04) | Medium | Alameda, Contra Costa | 111.4 | GSP Approved |
| Santa Clara Valley – Niles Cone (2-009.01) | Medium | Alameda, Santa Clara | 101.9 | no GSP in DWR GSP-areas layer |
| Santa Margarita (3-027) | Medium | Santa Cruz | 34.8 | GSP Approved |
| Santa Rosa Valley – Santa Rosa Plain (1-055.01) | Medium | Sonoma | 127 | GSP Approved |
| Santa Ynez River Valley (3-015) | Medium | Santa Barbara | 317.3 | GSP Approved |
| Scott River Valley (1-005) | Medium | Siskiyou | 99.7 | adjudicated (all or part, per DWR table); GSP Approved |
| Shasta Valley – Shasta Valley (1-004) | Medium | Siskiyou | 341 | GSP Approved |
| Sierra Valley – Sierra Valley (5-012.01) | Medium | Plumas, Sierra | 183.3 | GSP Approved |
| Tahoe Valley – Tahoe South (6-005.01) | Medium | El Dorado | 23.1 | no GSP in DWR GSP-areas layer |
| Ukiah Valley (1-052) | Medium | Mendocino | 58.7 | GSP Approved |
| Upper Santa Ana Valley – Temescal (8-002.09) | Medium | Riverside | 35.9 | GSP Approved |
| Ventura River Valley – Upper Ventura River (4-003.01) | Medium | Ventura | 8.2 | GSP Approved |
Frequently Asked Questions
What is SGMA basin priority?
Under California's Sustainable Groundwater Management Act (SGMA), the Department of Water Resources ranks each of the state's 515 groundwater basins and subbasins as high, medium, low or very low priority. In DWR's words, the rankings "provide an indicator of the overall relative importance of groundwater". In the 2019 prioritization, 46 basins are high priority, 48 medium, 11 low and 410 very low.
What does high or medium priority mean for my property?
DWR: "only high- and medium-priority basins are required to form a groundwater sustainability agency (GSA) and adopt a groundwater sustainability plan (GSP) or submit an alternative to a GSP. Low- and very low-priority basins may adopt these plans but are not required to." So a parcel in a high- or medium-priority basin falls under that basin's GSA and plan; the local rules and any fees vary by GSA. Priority itself is not a finding about your well or water.
Does a high priority mean the basin is in trouble?
Not by itself. DWR says the prioritization "does not provide an assessment on local groundwater management practices or basin sustainability" and that "a sustainably managed basin may still be designated as high-priority based on which of these factors are present." Critical overdraft is a separate designation (below).
What is a critically overdrafted basin?
DWR quotes SGMA: "A basin is subject to critical overdraft when continuation of present water management practices would probably result in significant adverse overdraft-related environmental, social, or economic impacts." 21 basins are on DWR's critically overdrafted list (Bulletin 118 Interim Update 2016, with 2018 boundary changes).
Do I pay SGMA fees on a household well?
Usually not. Water Code §10721(e) defines a "de minimis extractor" as "a person who extracts, for domestic purposes, two acre-feet or less per year", and §10730(a) says a groundwater sustainability agency "shall not impose a fee pursuant to this subdivision on a de minimis extractor unless the agency has regulated the users pursuant to this part." The State Water Board puts it this way: household well users who extract two acre-feet or less a year for domestic purposes only "are typically exempt from reporting and paying fees." A GSA with an adopted plan can also charge extraction fees under §10730.2, which has no de minimis carve-out, so check your local GSA's fee rules.
When must a basin be sustainable under SGMA?
Water Code §10720.7 required plans by January 31, 2020 for critically overdrafted high- and medium-priority basins and by January 31, 2022 for the other high- and medium-priority basins. §10727.2(b)(1) then gives each plan 20 years from implementation to reach its sustainability goal, which works out to about 2040 and about 2042. Those two years are not written in the statute, and DWR may grant extensions of up to five years (§10727.2(b)(3)(A)).
What is a probationary basin?
When a basin's plan is found inadequate, the State Water Board may designate a high- or medium-priority basin as probationary after notice and a public hearing (Water Code §10735.2). Tulare Lake and Tule are on probation as of November 2026; 4 other basins were reviewed and returned to DWR oversight without probation.
How do I check the basin for my exact parcel?
The ZIP lookup on this page gives the basins a ZIP's area overlaps, which is an approximation. For a parcel, use DWR's SGMA Basin Prioritization Dashboard or the Bulletin 118 basin map and zoom to the address. A parcel outside every mapped basin can still have a well (for example in fractured rock).
Source: California Department of Water Resources, SGMA 2019 Basin Prioritization and Bulletin 118 groundwater basin boundaries, accessed 2026-11-03. Prioritization file: DWR SGMA Basin Prioritization (SGMA 2019 Basin Prioritization (final 515 table, file dated 2022-04-21)); critically overdrafted list: DWR Bulletin 118. DWR says the 2019 prioritization “was completed in December 2019” and “No future basin prioritization projects are planned at this time”; all 515 priorities here matched DWR's live data on November 4, 2026. Verify a parcel's basin on DWR's dashboard before relying on it. ZIP areas: U.S. Census Bureau 2020 ZCTAs.