Hydrologic Changes Associated with Geothermal Development in Long V Alley Caldera, California

Abstract

Long VaHey caldera in east-central California is the site of a 40 MW binary-electric geothennal development utilizing water at temperatures of 170°C. Environmental impacts ofthis development include declines in hot spring discharge, increases in fumarolic discharge, vegetation kills from steam-heating, and land subsidence. A program of hydrologic monitoring to detect such changes has been in effect since 1988 under the direction of the Long Valley Hydrologic Advisory Committee. This committee has provided a useful forum in which monitoring data, both public and proprietary, can be discussed and consensus reached regarding the factors responsible for observed changes and the need for mitigation measures to minimize or prevent significant adverse impacts to existing thennal features.