Water in Wyoming.
Wyoming's small populations and geologically high natural arsenic produce localized exposure across many systems. Oil-and-gas wastewater incidents add risk in extraction regions.
How Wyoming regulates drinking water.
Federal SDWA primacy. No state MCLs stricter than federal. Active oil-and-gas wastewater oversight in Powder River Basin.
Wyoming Department of Environmental Quality — Water Quality Division
Wyoming's water history, in order.
The contamination events, regulatory shifts, and major settlements that define how this state thinks about drinking water today.
- 2011
EPA links Pavillion-area groundwater contamination to nearby fracking — first federal acknowledgment.
- 2016
Federal Pavillion fracking-contamination investigation handed back to state under industry pressure.
The actual water you drink.
The physical rivers, aquifers, lakes, and reservoirs that feed Wyoming's public water systems. Source quality is the foundation of tap quality — and where the long-term protection fights happen.
- riverNorth Platte River
Eastern WY supply.
- riverSnake River (Yellowstone)
NW WY.
- aquiferMadison Aquifer
Major regional groundwater source.
- aquiferPowder River Basin
NE WY with coal-bed methane impacts.
Source-water mix
~50% surface water, ~50% groundwater
Major cities served
Cheyenne · Casper · Laramie · Gillette
Who actually serves the water.
The largest public water systems in Wyoming by population served. Click your ZIP after to see the full live EWG report for your specific utility.
- Cheyenne Board of Public UtilitiesCheyenne65Kserved
- Casper Public UtilitiesCasper60Kserved
Where the contamination comes from.
Every state has a different industrial fingerprint. The industries below are the dominant historical and active contamination sources in Wyoming's drinking water systems.
Pavillion-area fracking-related groundwater contamination was the first federally acknowledged case linking fracking to drinking-water contamination. Coal-bed methane operations in Powder River Basin drive water-quality concerns. Limited PFAS contamination documented.
What state data flags most consistently.
Drawn from EPA SDWIS sampling records, EWG state summaries, and regional regulatory action over the past five years. Read the full deep dive on each.
Arsenic
A naturally occurring carcinogen. Highest in private wells and the rural Southwest.
Trihalomethanes (TTHMs)
Byproducts of chlorinating water. Linked to bladder cancer at chronic exposure.
Nitrate
Fertilizer and animal waste runoff. Acutely dangerous for infants under 6 months.
Risk isn't evenly distributed.
Pavillion-area residents face the most-documented fracking-related water contamination in the U.S. Rural well users statewide face geologic arsenic.
~25% on private wells. Pavillion-area wells have documented fracking-related contamination.
What's coming for Wyoming's water.
Snowpack decline reshapes Snake and North Platte summer flow. Wildfire burn-scar runoff threatens forested watersheds. Powder River Basin coal-bed methane water-quality concerns.
Voluntary statewide
WY DEQ provides voluntary technical assistance.
Five questions for your next Consumer Confidence Report.
Your utility is required to send you a Consumer Confidence Report annually. Most are dense and procedural. These are the questions worth following up on for Wyoming specifically.
- 1
If I'm in Pavillion area, has my well been monitored under federal or state oversight?
- 2
What is my private well's arsenic level?
- 3
Has my system reported any health-based violations in the past three years?
Most state regulators allow public records requests for the underlying lab reports behind your CCR — your utility should be able to provide them on request.
NSF/ANSI 58 reverse osmosis for arsenic, nitrate, and most VOC contamination.
We don't recommend brands — the NSF/ANSI certification number matters more than the name on the box.
This is the state. Your address is the answer.
State-level patterns don't tell you about your specific tap. Run your ZIP for the live EWG contaminant report on your utility — or build a personalized Water File for your household.
Source-water mix, utility counts, lead-service-line estimates, and private-well shares are approximate, drawn from EPA SDWIS public data and state primacy-agency summaries. Contaminant rankings reflect EWG state-level monitoring data and regional regulatory action — they are not exhaustive. Timeline events are publicly documented. See methodology for the full sourcing. Search EPA SDWIS for Wyoming