Geology topics

Kiyoshi J. Takasaki

Publications and source records attributed to Kiyoshi J. Takasaki.

3 recordsLinked to original sources

USGS1996

Water-quality reconnaissance of ground water in the inhabited outer islands of Chuuk State, Federated States of Micronesia, 1984-85

A reconnaissance of ground-water quality in 24 inhabited outer islands in Chuuk State was made between January 1984 and October 1985. Most of the islands are part of low-lying coral atolls within the Western, Namonuito, Hall, and Mortlock Island Groups. A total of 648 wells were located and sampled for temperature and specific conductance. A few miscellaneous sites such as taro patches also were sampled. The nitrate concentration was determined for 308 water samples. To develop a relation between specific conductance and chloride concentration, the chloride concentration was determined for 63 water samples. In addition, 21 water samples were analyzed for major and trace constituent ion concentrations. Chloride and nitrate are the primary constituents affecting the potability of ground water in the inhabited outer islands of Chuuk State. The source of chloride in ground water is seawater, whereas nitrate is derived from plant and animal waste materials. The chloride concentrations in many well waters exceed the World Health Organization guideline for drinking water, particularly in wells near the shoreline or on small islands. In addition, the nitrate concentrations in some well waters exceeded the World Health Organization guideline for drinking water.

Chuuk State↗

USGS1993

Ground Water in Kilauea Volcano and Adjacent Areas of Mauna Loa Volcano, Island of Hawaii

About 1,000 million gallons of water per day moves toward or into ground-water bodies of Kilauea Volcano from the lavas of Mauna Loa Volcano. This movement continues only to the northern boundaries of the east and southwest rift zones of Kilauea, where a substantial quantity of ground water is deflected downslope to other ground-water bodies or to the ocean. In the western part of Kilauea, the kaoiki fault system, which parallels the southwest rift zone, may be the main barrier to ground-water movement. The diversion of the ground water is manifested in the western part of Kilauea by the presence of large springs at the shore end of the Kaoiki fault system, and in the eastern part by the apparently large flow of unheated basal ground water north of the east rift zone. Thus, recharge to ground water in the rift zones of Kilauea and to the areas to the south of the rift zones may be largely by local rainfall. Recharge from rainfall for all of Kilauea is about 1,250 million gallons per day. Beneath the upper slopes of the Kilauea rift zones, ground-water levels are 2,000 feet or more above mean sea level, or more than 1,000 feet below land surface. Ground-water levels are at these high altitudes because numerous and closely spaced dikes at depth in the upper slopes impound the ground water. In the lower slopes, because the number of dikes decreases toward the surface, the presence of a sufficient number of dikes capable of impounding ground water at altitudes substantially above sea level is unlikely. In surrounding basal ground-water reservoirs, fresh basal ground water floats on seawater and, through a transition zone of mixed freshwater and seawater, discharges into the sea. The hydraulic conductivity of the dike-free lavas ranges from about 3,000 to about 7,000 feet per day. The conductivity in the upper slopes of the rift ranges from about 5 to 30 feet per day and that of the lower slopes of the east rift zone was calculated at about 7,000 feet per day. The occurrence of heated basal water south of the lower east rift zone of Kilauea indicates the movement of a large quantity of geothermally heated ground water southward from the rift zone. There is little indication of similar movement of water from the upper slopes of the east rift zone, and there is no obvious movement of heated water from the lower east rift to the north because of the absence of heated ground water north of the rift zone. A broad range in temperature and chemical composition of geothermally modified ground water indicates several different sources. Four possible sources are (1) cold meteoric water, (2) cold seawater, (3) hydrothermal fluids of meteoric origin, and (4) hydrothermally modified seawater. The chloride-ion to magnesium-ion ratio of ground water indicates whether the water has been geothermally modified. A ratio greater than 15 to 1 generally denotes geothermally modified ground water.

Open-File Report↗

USGS1981

Evaluation of major dike-impounded ground-water reservoirs, Island of Oahu, with a section on flow hydraulics in dike tunnels in Hawaii

Ground-water reservoirs impounded by volcanic dikes receive a substantial part of the total recharge to ground water on the island of Oahu because they generally underlie the rainiest areas. They accumulate the infiltration from rainfall, store it temporarily, and steadily leak it to abutting basal reservoirs or to streams cutting into them. The dike reservoirs have high hydraulic heads and are mostly isolated from saline water. The most important and productive of the dike-impounded reservoirs occur in an area of about 135 square miles in the main fissure zone of the Koolau volcano where the top of the dike-impounded water reaches an altitude of at least 1,000 feet. Water is impounded and stored both above and below sea level. The water stored above sea level in the area of about 135 square miles has been roughly estimated at 560 billion gallons by using a mean water level of 400 feet and a mean specific yield of 0.05. In comparison, the water stored above sea level in reservoirs with a mean water level of 300 feet and mean specific yield of 0.03 underlying a dike-intruded area of about 53 square miles in the Waianae Range has been roughly estimated at 100 billion gallons. Storage below sea level is indeterminable, owing to uncertainties in the ability of the rock to store water resulting from increasing dike density and decreasing porosity. Total leakage from storage in the WaLanae Range has not been estimated because underflow is difficult to determine. Much of the surface leakage, about 4 Mgal/d in the upper parts of Waianae, Makaha, and Lualualei Valleys, has been diverted by tunnels. Hence, supplies available, other than surface leakage, cannot be estimated from the discharge end of the hydrologic cycle. Infiltration in the Waianae Range to dike-intruded reservoirs in the upper part of the valleys on the west (leeward) side has been estimated at about 20 Mgal/d, and on the east (windward) side, at about 10 Mgal/d. The available supply has been estimated at about 15 Mgal/d from the infiltration on the leeward side, of which about 4 Mgal/d is now being developed. No estimate has been made for the available supply on the windward side. Dike-intruded reservoirs at shallow depths west (lee side) of the crest are in upper Makaha, Waianae, and Lualualei Valleys. They are at moderate depths in upper Haleanu and in lower Kaukonahua Gulches on the east (windward) side. Flow hydraulics in dike tunnels is also discussed.

Hawaii↗