Potential effects of the Hawaii geothermal project on ground-water resources on the Island of Hawaii

Abstract

Temp. of = 1.8(temp.°C) + 32 Definition of terms used: Aquifer-a permeable formation that stores and transmits ground water in sufficient quantity to supply wells. Anchialine pond-location along coastline where the groundwater table is exposed at the land surface in POroU1; lavas. These pools have no surface connection to the sea. Basal water-a freshwater lens floating on saltwater. Brackish (water)-water with salinity greater than that of fresh water and less than that of sea water. Brine-water with an unusually high concentration of salts. Darcy velocity-rate of flow of water per unit cross-sectional area. Evapotranspiration-a combination of evaporation from open bodies of water, evaporation from soil surfaces, and transpiration from the soil by plants. Hydraulic conductivity (K)-measure of the rate of flow of water per unit cross-sectional area under a hydraulic gradient of 1. (Hydraulic) head-height of water column in a well, above an arbitrary datum. Intrinsic permeability (k)-measure of the ability of a rock formation to transmit water, related to hydraulic conductivity (K) by the formula: K = kpg/p, where p is fluid density, g is gravitational acceleration, and u is fluid dynamic viscosity. Impounded water-ground water in compartments that form within a dike intrusion complex when water movement is slowed or stopped by dike rocks of low permeability. Littoral-the marine environment between the limits of high tide and low tide. v. . Perched water-ground water that accumulates above ash layers or other low-permeability volcanic material of limited areal extent located within the lava between the water table and the land surface. (Geothermal) reservoir-a permeable formation that stores and transmits thermal water in sufficient quantity to supply geothermal wells Saline-possessing more than 3,000 parts per million total dissolved solids. Transmissivity-a measure of the volumetric flow rate of ground water per unit width of reservoir for a unit hydraulic gradient. It is equal to reservoir hydraulic conductivity times reservoir saturated thickness. Unconfined-open to the atmosphere so that water drains from the pore space as water level is lowered. Vapor-static pressure-a column of steam whose pressure is controlled by the density of steam.

Groundwater chemistry in the vicinity of the Puna Geothermal Venture Power Plant, Hawai‘i, after two decades of production

“…After a series of tests, this well was used for power production beginning in 1981 and ending in 1989 (Thomas, 1987(Thomas, , 1990. During the 1980s and early 1990s, PGV or its predecessor companies drilled the nearby Kapoho State wells (KS series), some reaching depths in excess of 2.5 km, and began producing power in May 1993 (Sorey and Colvard, 1994). The PGV plant has been in operation since that time and has continued well drilling operations; for example, KS-13 in 2005 (Teplow andothers, 2009) Unlike the HGP-A installation, the PGV plant does not use infiltration ponds for liquids or engineered abatement for the produced gases under normal conditions, though abatement of H 2 S is carried out during emergencies that cause steam release to the atmosphere.…”

“…An early and on-going concern about geothermal development is the potential impact on local groundwater (for example, Iovenitti, 1990). To address this concern, a major scientific effort was carried out in the early days of well drilling and development to characterize existing hydrologic conditions in the region and delineate potential vulnerabilities (Iovenitti, 1990;Ingebritsen and Scholl, 1993;Sorey and Colvard, 1994;Janik and others, 1994;Gingerich, 1995;Scholl and others, 1995). The basaltic lava flows from Kīlauea and its rift zone vents provide highly permeable flow paths for groundwater, but vertical dikes within the upper rift zone constitute effective barriers.…”

“…On the other hand, the warm groundwaters lack some of the distinctive features in the chemical composition of the deep geothermal water. This fact and other information from drill cores and temperature profiles in deep wells led many investigators to conclude that direct leakage of water from the geothermal reservoir into groundwater was insignificant (Janik and others, 1994;Sorey and Colvard, 1994). The warm temperatures in groundwater wells and coastal springs were commonly attributed to conductive heat transfer.…”

“…The warm temperatures in groundwater wells and coastal springs were commonly attributed to conductive heat transfer. Although some direct leakage of reservoir steam and sulfur-rich gas was proposed to account for the elevated temperatures and sulfate concentrations in shallow monitoring wells in the LERZ (Janik and others, 1994;Sorey and Colvard, 1994), a discharge pathway for hot water from the reservoir was not identified.…”

“…A follow-up monitoring program was recommended (Sorey and Colvard, 1994) for detection of any impacts from producing the hot reservoir fluids or from injecting the cooled water back into the deep reservoir. As a condition of the underground injection control permit (UH-1529), PGV must conduct a hydrologic monitoring program.…”