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K. J. Takasaki

Publications and source records attributed to K. J. Takasaki.

13 recordsLinked to original sources
USGS1989

Ground-water resources of selected high volcanic islands of Truk with emphasis on small village supplies

Existing water supply sources in the Truk State were assessed. The first part of the assessment includes the high islands in the Truk Lagoon and the second part includes the principal inhabited outer islands of the Truk State. The high islands in the lagoons are remnant peaks of a partly sunken volcano. Coral atolls form the periphery of the lagoon. The islands are composed of tight, massive lavas and cemented rock fragments. Although saturated, the rocks yield little water to springs or wells. Weathering causes some increase in permeability, and where the weathering is the deepest as in valleys, these materials make up the main reservoirs of groundwater. Rainfall averages about 140 inches/yr and is sufficiently persistent to provide water for drinking and cooking from small rain catchments, springs and seeps with little or no storage. This situation is not desirable because rainless periods, even short ones, cause springs, seeps, and rain barrels to go dry quickly. (USGS)

Water-Resources Investigations Report↗
USGS1986

Ground-water yield and potential for irrigated agriculture in the area of the Naval Magazine and Radio Transmitting Facility, Lualualei, Oahu, Hawaii

An estimated additional 2 million gallons per day (mgd) of fresh and slightly brackish water can be developed in Lualualei Valley , Hawaii, for the agricultural outleasing project. Several of these wells could be located in the volcanic aquifer which presently produces water of excellent quality. A secondary line of wells designed to develop water from the Coralline aquifer would capture the flow not captured by the wells in the volcanic aquifer. The chloride concentration of the water pumped from these wells is expected to range between 500 and 1,500 mg/L. The amount of acreage devoted to crops would depend primarily on the water quality and quantity requirements of the type of crops cultivated and on the type of irrigation system employed. The remaining acreage could be allocated for pasture to graze beef cattle. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1986

Results of exploratory drilling for water in Waihanau Valley, Molokai, Hawaii

Three exploratory wells, located in lower Waihanau Valley on Molokai, were drilled and tested for their yields during the period May to October 1983. The first well, 582 ft deep, tapped the main water body in a basaltic aquifer intruded by scattered near-parallel volcanic dikes. Water in this water body is impounded by the dikes and has a head of about nine feet above sea level. A 48-hour pumping test was conducted on this well. The well was pumped at various rates ranging from 144 to 455 gal/min for nine hours. Thereafter, the well was pumped for 39 hours at a rate of 156 gal/min approximating the planned operational rate of 150 gal/min. The specific capacities of the well at the rates pumped averaged about 30 gal/min/ft of drawdown. The temperature of the pumped water remained nearly constant at 69 F (20.5 C). The chloride concentration ranged from 19 to 22 mg/L during the test. Analyses of the chemical constituents and trace metals of the water pumped indicated that it was of excellent quality. Based on these results, the well was finished as a production well. A shallow water body perched about 30 ft below ground surface and more than 400 ft above the main water body was discovered during the drilling of the first well when about 50 gal/min of water cascaded down the well. Two wells were drilled to depths of 200 and 150 ft, respectively, to explore this perched water. The yields obtained from this perched water body were low and indicated that its development was not feasible. (Author 's abstract)

Water-Resources Investigations Report↗
USGS1982

Water resources of southeastern Oahu, Hawaii

Southeastern Oahu comprises the eastern end of the Koolau Range and is divided into two roughly equal parts by the crest of the range. The northside of the crest is commonly called the windward side and the southside, the leeward. Precipitous cliffs aproned by a gently sloping landscape are the main topographic features on the windward side. The leeward side is a gentle lava-flow slope incised by steep narrow valleys. The main Koolau fissure zone, including the caldera, lies on the windward side. The leeward side includes minor rift zones that are perpendicular to and intersect the main fissure zone. Dikes in the main fissure zone strike from nearly east-west in the eastern end to about N. 55? W. in the western part. Dikes in the minor rift zones strike from north-south to slightly northeasterly. Water use is about 18 Mgal/d (million gallons per day) of which only 4 Mgal/d is obtained locally from ground-water sources. About a third of the 14 Mgal/d deficit is imported from sources northwest of the study area on the windward side and the remainder from sources in the Honolulu and Pearl Harbor areas on the leeward side. The 4 Mgal/d being developed represents only about 3 percent of the area's rainfall compared to a development-rainfall ratio of 20 percent for the rest of the island. Streams are short and flashy. Perennial streamflow to the sea occurs only in Maunawili Valley and in the Waimanalo area. Mean annual discharge is estimated at 20 Mgal/d in the windward side and at 15 Mgal/d on the leeward side. Low flow, expressed as the flow that is equaled or exceeded 90 percent of the time, is 5 Mgal/d windward of the crest and zero leeward of it. Most fresh ground water occurs in lava flows of the Koolau Volcanics. It is impounded by dikes in the rift zones and floats on saline ground water as lenses outside the rift zones. Small but important bodies of freshwater are perched in volcanic rocks of the Honolulu Group in Maunawili Valley. Fresh ground water occurs in near-shore calcareous sands that overlie a clay horizon in the Waimanalo area. Deeply buried talus and alluvium also carry fresh ground water in the Waimanalo area. Wells tapping saline ground water in fresh lava flows of the Honolulu Group provide water for a sea-life park in the Makapuu area. The same aquifer is tapped by wells for disposal of the saline waste water. The current development scheme in the windward side that utilizes only the free-flow equilibrium discharge of dike-impounded water is inefficient and does not cope with the annual weather cycle. The flow available for development under this scheme is greatest in the rainy winter months when demand is the lowest and least in the summer months when demand is the highest. A more optimal scheme would be to change this natural flow pattern by depleting storage by pumping to increase flow in the high-demand summer months and allowing the depleted storage to recover naturally in the low-demand winter months. Depleting storage would lower water levels which would provide more room for infiltration and provide less opportunity for evapotranspiration. The basal-water reservoir in the leeward side is isolated hydrologically from abutting reservoirs outside the area and can and should be fully exploited. The existing development of the basal-water reservoir is small compared to the natural ground-water flow and that part not being developed is wasting to the sea. Because the area is hydrologically isolated, development will not be detrimental to or reduce the ground-water supply outside the area.

Open-File Report↗
USGS1978

Summary appraisals of the nation's ground-water resources – Hawaii region

The water resources of the Hawaii Region, taken as a whole, are far greater than foreseeable future demands on them, but this is not so for the individual islands. Each and every island is independent with respect to water supply, and the occurrence and availability of water vary widely from island to island. The ground-water resources offer better prospects for supplying additional water needs in the future than the surface-water resources. Most of the surface supplies that are easy to develop have been fully utilized where needed, and conduits and reservoirs necessary to develop new or additional supplies would generally require large and perhaps prohibitive outlays of capital. In 1975, ground water supplied 46 percent, and surface water 54 percent of the water needs but, in the years ahead, these percentages will likely be reversed as more ground-water development takes place. Total water use, in 1975, averaged about 1,775 million gallons per day, ofwhich about 810 million gallons per day was ground water. The total water use is divided into public supply, 11 percent; self-supplied industrial use, 23 percent; and agricultural, 66 percent. Rainfall is the principal source of ground-water recharge. Local mean annual rainfall ranges from less than 20 inches to more than 300 inches, with the annual average rainfall on the large islands exposed to the trade winds being slightly more than 73 inches and that on the small islands situated in the rain shadow of the larger islands being less than 26 inches. Ground-water recharge has been estimated at about 2,400 billion gallons per year (6.5 billion gallons per day) or roughly 30 percent of the rainfall. Most fresh ground water in the region is stored below sea level in porous lava flows, much of it as basal-water lenses floating on saline ground water, as distinguished from dike-impounded water in the interior of the islands. The basal-water lens is maintained by recharge, which, if reduced, leads to thinning of the lens and subsequent encroachment of seawater. Seawater is the biggest pollutant of freshwater, and many of the ground-water problems are, in some way, associated with the encroachment of saline water induced by development. The major problem areas include the entire island of Oahu, south Kohala-Kona coast on the island of Hawaii, Lahaina District in Maui, and the Koloa and Kekaha-Mana areas in Kauai.

Hawaii↗
USGS1969

Water in the Kahuku area, Oahu, Hawaii

The Kahuku area comprises the north end of the Koolau Range and its bordering coastal plain. This part of the range is less deeply eroded than oth3r parts, and except for long, narrow valleys and cliffs near the shore, it has retained the general shape of the original volcanic dome. A 21/2-mile-wide dike zone of parallel and subparallel dikes along the crest is the remnant of the fissure zone of eruption. Outcrops are mostly permeable lava flows of the Koolau Volcanic Series, which are intruded by dikes inside the dike zone and are free of dikes outside it. The lava flows constitute main aquifers, and water bodies in them are called dike water inside the dike zone and basal water outside it. Dikes, because they are less permeable than the lava flows they intrude, impound ground water, thereby controlling its movement, discharge, and storage. The top of the dike-impounded water is at an altitude of at least 1,000 feet near the south end of the Kahuku area. Dike water is discharged as leakage, the amount of which fluctuates in response to changes in storage, as flow into streams, where they intersect saturated rock, and as underflow to the basal-water body. Basal water occurs on either side of the dike zone, which forms both a structural and hydrologic boundary. It is artesian on the windward side wherever it underlies the coastal plain, and the altitude of water levels ranges from 7 to 22 feet. Leeward of the dike zone, basal water occurs only under water-table conditions because of the near absence of a coastal plain, and the altitude of water levels ranges from less than 1 foot to about 3 feet. The quality of dike water is excellent except near the north end. where it is slightly contaminated by infiltration of irrigation water that contains as much as 1,200 mg/1 (milligrams per liter) chloride. Irrigation water is also a source of contamination of the basal-water body. The major contaminant, however, is sea water, which underlies the basal-water body. In the Kahuku subarea--where pumpage from the basal-water body is greatest--sea-water contamination is a major concern. Natural contamination by encroaching sea water extends more than 2 miles inland in the Waimea-Kawela subarea and generally precludes development of large quantities of basal water. At low altitudes where the perennial flow is small, all streams are intermittent except Kaluanui and Kamananui. Some streams are perennial in their upper reaches because of persistent rainfall, and some are perennial in their middle reaches owing to the discharge of dike water; however, most flows are small in the lower reaches because most of the flow has infiltrated into the ground-water reservoir. For these reasons, streamflow cannot be economically developed and is not a reliable source of water supply. Average rainfall is about 240 mgd (million gallons per day). Of this amount, about 220 mgd is in the mountains. On .the basis of a rainfall input of 220 mgd and estimates of stream runoff and evapotranspiration, ground-water flow is estimated to be 85 mgd, a figure which compares favorably with estimates based on analyses of pumping-test data. Of this amount, an average of 30 mgd is discharged by wells and the remaining 55 mgd is eventually discharged to the sea by underflow or to the atmosphere by evapotranspiration. The most promising areas for developing basal water are in the Hauula and Laie subareas, where draft is low and ground-water flow is high. The Waimea-Kawela subarea is not promising owing 'to low ground-water flow even though draft is low. Least promising for development is in the Kahuku subarea where an overdeveloped condition prevails in which draft for sugarcane irrigation exceeds the ground-water flow. The development of dike water is promising in the Waimea-Kawela subarea where ground-water flow greatly exceeds the draft.

Water Supply Paper↗
USGS1969

Water resources of Windward Oahu, Hawaii

Windward Oahu lies in a large cavity--an erosional remnant of the Koolau volcanic dome at its greatest stage of growth. Outcrops include volcanic rocks associated with caldera collapse and the main fissure zone which is marked by a dike complex that extends along the main axis of the dome. The fissure zone intersects and underlies the Koolau Range north of Waiahole Valley. South of Waiahole Valley, the crest of the Koolau Range is in the marginal dike zone, an area of scattered dikes. The crest of the range forms the western boundary of windward Oahu. Dikes, mostly vertical and parallel or subparallel to the fissure zone, control movement and discharge of ground water because they are less permeable than the rocks they intrude. Dikes impound or partly impound ground water by preventing or retarding its movement toward discharge points. The top of this water, called high-level water in Hawaii, is at an altitude of about 1,000 feet in the north end of windward Oahu and 400 feet near the south end in Waimanalo Valley. It underlies most of the area and extends near or to the surface in poorly permeable rocks in low-lying areas. Permeability is high in less weathered mountain areas and is highest farthest away from the dike complex. Ground-water storage fluctuates to some degree owing to limited changes in the level of the ground-water reservoir--maximum storage is about 60,000 million gallons. The fluctuations control the rate at which ground water discharges. Even at its lowest recorded level, the reservoir contains a major part of the storage capacity because most of the area is perennially saturated to or near the surface. Tunnels have reduced storage by about 26,000 million gallons--only a fraction of the total storage--by breaching dike controls. Much of the reduction in storage can be restored if the .breached dike controls are replaced by flow-regulating bulkheads. Perennial streams intersect high-level water and collectively form its principal discharge. The larger streams are those that cut deepest into high-level reservoirs. Except near the coast in the northern end of the area, where dikes are absent, total base flow of streams equals total ground-water discharge. Development of high-level water by tunnels and wells diverts ground-water discharge from streams, decreasing the base flow of these streams. Construction of Haiku tunnel decreased the flow of Kahaluu Stream, 2 ? miles away, by about 26 percent. The dependable flow of water is estimated at 118 mgd (million gallons per day), of which 84 mgd is discharged by streams, tunnels, springs, and wells The remaining 34 mgd is underflow, most of it discharging into the sea near the northern end of ,the area. Average flow is estimated at 220 mgd, of which 159 mgd is. inventoried flow and 61 mgd is estimated underflow. Specific capacity of wells tapping lava flows of the Koolau Volcanic Series ranges from less than 1 to 11 gallons per minute per foot of drawdown in the dike-complex zone and from 2 to 100 in the marginal dike zone. A transmissivity of 4,000,000 gallons per day per foot was determined for the basal aquifer. Permeabilities of rocks in high mountainous areas penetrated by water-development tunnels were compared by recession constants determined from free-flow drainage. Evapotranspiration was estimated from regression curves obtained by correlating median annual rainfall and median annual pan evaporation. Evapotranspiration values from these curves compared favorably w4th values obtained from water-budget listings of rainfall and measured ground-water flow. The chemical quality of water in wells and tunnels tapping rocks of the Koolau and Honolulu Volcanic Series is excellent. Except in a few isolated areas near the shore, the chloride content of the water from these sources is generally less than 100 parts per million. Wells tapping calcareous materials are subject to sea-water contamination under heavy pumping.

Water Supply Paper↗