B-39 An Appraisal of Colorado’s Geothermal Resources


Bulletin B-39 was re-released in 2006. It was first published in 1978 and contains a description of each of the 56 geothermal areas known in 1978 and an explanation of the various geothermometric methods used to estimate the geothermal reservoir temperatures of each area. Because of the increase in price of oil and natural gas during the 2000s, the Colorado public is once again searching for cheap, reliable, and renewable energy sources. Geothermal resources in Colorado may offer opportunities to produce electricity using technologies not available in the 1970s. The objective of this publication is to provide readily accessible information on geothermal resources in Colorado to resource developers, government planners, along with interested businesses and citizens. Digital PDF download. B-39D


The Colorado Geological Survey (CGS) in conjunction with the US Geological Survey (USGS) in 1975 initiated a two-year evaluation of the geothermal resource potential of Colorado as determined by the usage of hydrogeological and geochemical data and geothermometer models. The geothermal resource potential of Colorado is expressed in numerous thermal springs and wells found throughout the western one-half of the state. In most instances the thermal waters of Colorado are unused, with minor amounts of thermal waters being used for recreation, space heating, domestic, and miscellaneous agricultural purposes. Although many energy companies have expressed interest in the geothermal resources of Colorado and have acquired leases to federal, state, and private lands, no large scale development has yet occurred.

During the investigation, 127 thermal springs and wells (temperatures in excess of 20°C (68°F)) were located, and field measurements of such physical parameters as discharge, pH, conductivity, and temperature were made. Water samples were collected for wet chemical and atomic absorption analysis and sent to the USGS, Water Resources Division Central Laboratory in Salt Lake City, Utah, or to Atlanta, Georgia. Spectrographic analyses were performed at the Denver Analytical Laboratory of the USGS. Samples were also collected and sent to the US Environmental Protection Agency (EPA) Radiological Laboratory in Las Vegas, Nevada, for determination of radioactive elements.

Evaluation of the field data shows that there are 49 distinct thermal areas within the state consisting of one or more groups of springs or wells. The temperature of the springs varied from a low of 20°C (68°F) at a number of springs to a high of 83°C (181°F) at Hortense Hot Spring, southwest of Buena Vista. The discharge of the waters varied from a low of less than 0.06 l/s (>1 gallon per minute (gpm)) to a high of 143 l/s (2,263 gpm) at the Big Spring in Glenwood Springs. The total dissolved solids of the waters varied from a low of 91 mg/l (91 ppm) at Spring B at Eldorado Springs, southwest of Boulder to a high of 21,500 mg/l (21,500 ppm) at Graves Spring in Glenwood Springs.