All chemical data for geothermal fluids in Idaho available as of December 1981 is maintained on GEOTHERM, computerized information system. This report presents summaries and sources of records for Idaho. 7 refs. (ACR)

This compilation contains chemical data for geothermal fluids in Idaho available as of December, 1981. The 951 records contain data on location, sample description, analysis type, collection condition, flow rates, and the chemical and physical properties of the fluid. Stable and radioactive isotope data are occasionally available. 6 refs.

This report follows the study to recognize, characterize, and delineate mineralized environments in the Wallace and Choteau quadrangles of Idaho and Montana.

From purposes and approach of study: The primary purposes of this study were to: (1) Define, on a reconnaissance level, current (1980) water-quality conditions in major aquifers (water-yielding rock formations) in the western Snake River basin, Swan Falls to Glenns Ferry; (2) summarize and interpret available geologic and hydrologic data to assist in understanding the natural and man-cause factors that affect present and future understanding the natural and man-caused factors that affect present and future water-quality conditions; and (3) establish a hydrologic data base on which future data can be compared to evaluate changes. A secondary purpose was to evaluate the possible effects percolation of thermal water applied for irrigation may have on the quality of local, less mineralized, nonthermal ground water.

From purposes of approach of study: The purposes of this study were to: (1) Define, on a reconnaissance level, current (1979) water-quality conditions in major aquifers (water-yielding rock formations) in the eastern Snake River basin; (2) present available geologic and hydrologic data to assist in understanding the natural and man-caused factors that affect water-quality conditions; and (3) establish a hydrologic base upon which future comparisons can be made to evaluate changes.

The geothermal resource of southern Idaho as assessed by the U.S. Geological Survey in 1978 is large. Most of the known hydrothermal systems in southern Idaho have calculated reservoir temperatures of less than 150 C. Water from many of these systems is valuable for direct heat applications. A majority of the known and inferred geothermal resources of southern Idaho underlie the Snake River Plain. However, major uncertainties exist concerning the geology and temperatures beneath the plain. The largest hydrothermal system in Idaho is in the Bruneau-Grang View area of the western Snake River Plain with a calculated reservoir temperature of 107 C and an energy of 4.5 x 10 to the 20th power joules. No evidence of higher temperature water associated with this system was found. Although the geology of the eastern Snake River Plain suggests that a large thermal anomaly may underlie this area of the plain, direct evidence of high temperatures was not found. Large volumes of water at temperatures between 90 and 150 C probably exist along the margins of the Snake River Plain and in local areas north and south of the plain.