Geothermal prospecting & hot wells
Hot springs are the surface clues to heat below. This page maps every recorded U.S. hot spring temperature as a heat map, with the official geothermal maps and the basics of drilling for hot water.
Heat map of recorded spring temperatures
Brighter areas mean more and hotter recorded springs (NOAA thermal springs list plus USGS-named hot springs). Click the map to open the nearest springs. This shows surface evidence only. Deep heat can exist where no spring reaches the surface.
Official geothermal maps
- USGS: Geothermal resource favorability, western U.S.: statistical favorability maps (data download).
- NREL Geothermal Prospector: interactive map of temperature at depth, heat flow, wells and resources.
- SMU Geothermal Laboratory: the national heat flow map of the U.S.
- OpenEI: Mapping geothermal potential in the western U.S.
- State geological surveys publish detailed local studies, for example the Colorado Geological Survey's Idaho Springs geothermal assessment.
Hot well basics
- Look for clues: nearby hot springs, travertine or sinter deposits, warm water wells, snow-free ground, faults and young volcanic rock.
- Temperature rises with depth about 25–30°C per kilometer on average, far faster near faults and hot springs.
- Water rights and permits: geothermal fluids are regulated by the state engineer or water resources agency in most western states. Get a permit and a licensed driller before drilling.
- Test the water for arsenic, fluoride, boron and lithium before using it for bathing pools or drinking. How to test.
- Look at listings with existing hot wells and water rights in Springs & hot wells for sale.
Need a well drilled?
JCC LLC (Joseph's Carpentry & Construction), the team behind AllSprings, owns well-drilling equipment. Email jccllc.apps@gmail.com about water or geothermal well projects.