Can you drill a well without a permit in Montana?

Exempt up to a limit. Montana's exempt-well exception (85-2-306 MCA) was tightened after Upper Missouri Waterkeeper v. DNRC (2024), and from Jan 1, 2026 appropriators must file a Notice of Intent with DNRC before putting exempt groundwater to use.

Which Montana counties have groundwater restrictions?

17 Montana counties sit in a managed, over-appropriated, adjudicated, or critically overdrafted groundwater basin — including Missoula County, Ravalli County, Sanders County, Fallon County, Gallatin County. Each county profile cites the specific basin and rule.

Montana · off-grid water rights

Water rights in Montana

Whether a new off-grid home can legally get its own water in Montana: the state well and water-rights rules, then the 17 counties where a specific groundwater basin adds a catch — each cited to the state water agency.

Montana water rules

Household well
Exempt up to a limit
Montana's exempt-well exception (85-2-306 MCA) was tightened after Upper Missouri Waterkeeper v. DNRC (2024), and from Jan 1, 2026 appropriators must file a Notice of Intent with DNRC before putting exempt groundwater to use.
Limit: 35 gpm or less AND ≤10 acre-ft/yr; a combined appropriation exceeding 10 acre-ft needs a permit regardless of flow rate
Montana DNRC — Water Rights Permit Exceptions (Exempt Wells) ↗
Greywater reuse
permitted
2007 law legalized single-family reuse but systems require approval.
Greywater Action / EPA REUSExplorer ↗
Rainwater harvesting
unrestricted
No state restrictions.
NCSL ↗
Water rights
prior appropriation
Prior appropriation; small domestic/stock wells (<35 gpm) generally exempt.
National Agricultural Law Center ↗

17 constrained counties in Montana

Closed to new supplyMissoula CountyHayes Creek Basin Controlled Groundwater Area66
Closed to new supplyRavalli CountyLarson Creek Controlled Groundwater Area68
Closed to new supplySanders CountyBNSF Paradise Railyard Controlled Groundwater Area77
Over-appropriatedFallon CountySouth Pine Controlled Groundwater Area45
Over-appropriatedGallatin CountyYellowstone Compact Controlled Groundwater Area76
Over-appropriatedMadison CountyYellowstone Compact Controlled Groundwater Area71
Over-appropriatedPark CountyYellowstone Compact Controlled Groundwater Area69
Over-appropriatedPowder River CountyPowder River Basin Controlled Groundwater Area55
Over-appropriatedPrairie CountySouth Pine Controlled Groundwater Area40
Over-appropriatedSweet Grass CountyYellowstone Compact Controlled Groundwater Area65
Over-appropriatedWibaux CountySouth Pine Controlled Groundwater Area44
Actively managedDeer Lodge CountyWarm Springs Ponds Controlled Groundwater Area66
Actively managedFlathead CountyBNSF Somers Site Controlled Groundwater Area67
Actively managedLewis and Clark CountyNorth Valley Controlled Groundwater Area (East Helena)76
Actively managedSilver Bow CountyButte Alluvial & Bedrock Controlled Groundwater Area66
Actively managedStillwater CountyHorse Creek Controlled Groundwater Area66
Actively managedYellowstone CountyLockwood Solvent Groundwater Plume Controlled Groundwater Area56

Keep exploring Montana

See the full Montana county ranking, compare states on the water-rights hub, or read how we score water access. We dim physical water — never erased — where a county sits in one of these basins, household-first.

General guidance, not legal advice. Off-grid, building, and land-use rules are often set at the county level and change often. Verify with your county and state before acting. Data reviewed 2026-06-26.