Data Methodology

Soak Trail maps natural hot springs across the American West. Here's how we collect, verify, and present that data.

Data Sources

Our spring database draws from several primary sources:

  • USGS Water Quality Portal — temperature, pH, mineral concentration, and discharge data from government-monitored sites.
  • OpenStreetMap — geographic coordinates, access types, and infrastructure data.
  • Forest Service and BLM records — land access status, seasonal closures, and fee information.
  • Field visits and photographer reports — first-hand observations from Soak Trail contributors.
  • Community submissions — corrections and additions from users, moderated and verified before publication.

What We Map

Each spring in our database may include:

  • Geographic coordinates (latitude/longitude)
  • Water temperature (°F)
  • Access type (paved, dirt road, 4WD, hike-in, resort, boat)
  • Development level (primitive, developed, resort)
  • Fee status and amount
  • Clothing policy
  • Dog policy
  • Seasonal availability
  • Nearest town and driving distance
  • Water chemistry (where USGS samples exist)

Not every spring has complete data. We indicate what's verified, what's estimated, and what's unknown.

Verification Process

We use a tiered verification system:

  • Source-verified — data confirmed by USGS records, government databases, or published research.
  • Field-verified — confirmed by a Soak Trail contributor's on-site visit with documentation.
  • Community-reported — submitted by users, reviewed by our team, pending independent verification.
  • Unverified — imported from public datasets (OSM, GNIS) without additional confirmation.

Each spring page shows its verification status and last-updated date. We encourage users to report corrections.

Temperature Data

Water temperatures come from USGS monitoring data, published surveys, or field measurements. Temperatures are point-in-time readings — natural springs fluctuate seasonally and after seismic events. A spring listed at 102°F may read 96°F in early spring or 108°F after a dry summer.

We classify springs into temperature bands:

  • Soakable (95–110°F) — comfortable for most people.
  • Warm (80–94°F) — pleasant but not hot.
  • Very hot (111–150°F) — requires caution; cool before entering.
  • Boiling / geyser (151°F+) — not safe for soaking.

Water Chemistry

Where USGS water-quality samples exist, we report mineral concentrations (calcium, magnesium, sodium, sulfate, chloride, iron), pH, and total dissolved solids.

Health-related language on mineral pages is intentionally cautious. Drinking-water standards (EPA, WHO) govern ingestion, not dermal soaking. Balneology research is mixed in quality. We cite sources and avoid unverified therapeutic claims.

What We Don't Do

  • We don't inflate counts with duplicate or low-quality records.
  • We don't claim a spring is "open" without evidence.
  • We don't make medical or therapeutic claims about soaking.
  • We don't sell placement or rankings.

Geothermal Heat-Flow Data

Our interactive map includes a modeled geothermal heat-flow overlay from the Stanford Thermal Earth Model (Aljubran & Horne, 2024), used under Creative Commons Attribution 4.0.

Heat-flow values (measured in mW/m²) describe regional subsurface heat movement — they do not indicate spring-water temperature, safety, accessibility, or whether a spring is currently flowing.

Corrections and Contributions

Found an error? Know of a spring we're missing? Have updated access information? We welcome contributions from the soaking community.