A conceptual model of shallow groundwater flow within the lower east rift zone of Kilauea Volcano, Hawaii

Abstract

The discovery, development, and production of geothermal energy within the lower east rift zone (LERZ) of Kilauea volcano has been the impetus for development of models of shallow groundwater flow within the LERZ. During the last twenty years several models have been proposed. Each has drawn upon the preceding model, and has refined and improved upon it as new data became available. The purpose of this thesis research is to again refine the conceptual model of LERZ shallow groundwater flow using data from newly drilled wells and a data set acquired through continuous weIl monitoring, an approach which has not previously been used in the LERZ. The objectives of this research are twofold; first, the conceptual model will characterize the shallow unconfined aquifer present within the LERZ and lower south flank (LSF) in its natural state of dynamic equilibrium. Second, with commercial geothermal production beginning in this area, the data contained in this thesis will be used as a baseline to asses the impact, if any, of production and reinjection of geothermal fluids on the shallow LERZ groundwater aquifer. This research utilizes geochemical analyses from several recently drilled LERZ wells, as well as temperature, pressure, and conductivity data acquired through continuous monitoring of five wells on the lower north flank (LNF), LERZ, and the LSF of Kilauea. These data are used to characterize water level, temperature, and conductivity responses to recharge events; develop transmissivity and hydraulic conductivity values for the LNF, LERZ, and LSF; delineate groundwater flow paths within the LERZ; establish the percentage of geothermal fluid mixed with groundwater in various LERZ wells; estimate the temperature of the reservoir or reservoirs from which this geothermal fluid is derived; and identify the origin of their thermal fluids as either fresh or salt water.