WRRC Technical Reports

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    WRRCTR No.41 Electrodialysis for Desalting Hawaiian Brackish Ground Water: A Field Study
    (Water Resources Research Center, University of Hawaii at Manoa, 1970-07) Lau, L. Stephen ; Chou, James C.S.
    A field study was made to evaluate the applicability and problems of desalting brackish ground water from basaltic and reef limestone aquifers in Honolulu, Hawaii with the electrodialysis process. The three-week study indicated that the brackish water at both sites was upgraded to potable quality and the rejection of ionized salts was above 80 percent. No pretreatment was necessary. Both the average production and rejection rates were about 420 gpd. An economic evaluation was not determinable from the short-term results.
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    WRRCTR No.42 Instantaneous Unit Hydrograph Analysis of Hawaiian Small Watersheds
    (Water Resources Research Center, University of Hawaii at Manoa, 1970-08) Wang, Ru-Yih ; Wu, I-Pai ; Lau, L. Stephen
    The analysis of about 240 flood hydrographs of 29 small watersheds on the island of Oahu, Hawaii, shows some unique hydrologic characteristics. A typical Hawaiian small watershed has a small area, flash peak, short time to peak, and small recession constant. Most of the hydrographs have the typical shape of a steep triangle. Based on statistical analysis of the observed flood hydrographs, a linear relationship has been found between peak discharge and the volume of runoff for each watershed. Because of the similar shape of the semi-dimensionless hydrographs, a unit-hydrograph with uncertain duration can be developed for each small watershed. The duration of such unit hydrographs can be determined by using the S-hydrograph technique with the equilibrium discharge as a criterion and the trial-and-error method utilizing a digital computer. The durations of the unit hydrograph, or the effective rainfall durations for Hawaiian small watersheds, were found to range from 5 minutes ot one hour. A good correlation has been found to exist between effective rainfall duration and the watershed area. Such a short duration unit hydrograph can be used to develop an instantaneous unit hydrograph by using Nash's conceptual model and the method of moments, assuming the effective rainfall is uniformly distributed with respect to time and space. The instantaneous unit hydrgraph for each watershed can then be solved by a computer. The two instantaneous unit hydrograph parameters, Gamma function argument, N, and reservoir storage constant, K, were found to correlate with areas of small watersheds. The instantaneous unit hydrograph of a given ungaged area can be determined by knowing the area of the watershed. The flood hydrograph with a given duration can also be solved by applying the incomplete Gamma function. The superposition characteristics of a linear model can be applied for hydrograph analysis of Hawaiian small watersheds. Hence, the design discharge with certain recurrence years for different engineering purposes can be directly multiplied with the design runoff, which may be obtained with the reference of the rainfall depth-frequency-duration charts and soil conditions for certain areas. A hydrograph study using an instantaneous unit hydrograph provides a good approach for hydrologic research since the short duration of effective rainfall is close to the duration caused by an instantaneous burst of rainfall. The study also synthesizes the parametric hydrograph which simplifies hydrograph analysis.
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    WRRCTR No.44 Identification of Irrigation Return Water in the Sub-surface, Phase III: Kahuku, Oahu and Kahului and Lahaina, Maui
    (Water Resources Research Center, University of Hawaii at Manoa, 1970-12) Tenorio, Pedro A. ; Young, Reginald H.F. ; Burbank, Nathan C Jr. ; Lau, L. Stephen
    This study continued the joint research effort undertaken by the Water Resources Research Center and the Honolulu Board of Water Supply in 1967 to investigate the physical and chemical characteristics of irrigation return water. Initial work concentrated on the Pearl Harbor-Waipahu area of Oahu. The phases reported herein included both Kahuku Plantation on Oahu and the sugar cane cultivation areas of central and West Maui (Pioneer Mill Co. and Hawaiian Commercail and Sugar Co.). Composite well, spring, and stream samples were taken and analyzed in the laboratory for the following constituents: bicarbonate, calcium, magnesium, phosphate, silica, boron, chloride, nitrate, sodium, potassium, bromide, flouride, sulfate, and total hardness. On the basis of increased index constituents over uncontaminated ground-water sources used to identify the presence of irrigation return water, it is evident, as previously concluded by Visher and Mink (1964), such irrigation return water, is definitely present in the basal water bodies underlying the three study areas. Considerable increases in the nitrate and sulfate indices, especially, and in the bicarbonate and silica indices, as shown by various methods of interpretation of water quality data obtained over a period of approximately two years or exceeding one complete cycle of plainting and harvesting of sugarcane, verify the strong influence of irrigation agricultural practices in altering the overall quality of the basal water sources in the three areas. The basal water quality of the HC&S aquifer is most affected regionally, as well as locally, by the prevailing agricultural practices. The deterioration of the water is dues in part to fertilization and to a greater exten to heavy pumping and recycling of the basal water. Water quality in the Pioneer Mill area parallels that of HC&S, although on a regional basis, the basal water quality, unlike that of the Pioneer Mill area, is not as deteriorated. Local effects of pumping are also especially noticeable in the Pioneer Mill area. Ground-water quality in the Kahuku area shows the obvious presence of irrigation return water indices, but, unlike the two plantations on Maui, the magnitude of the increases relative to uncontaminated water sources is considerably smaller. The effect of fertilization on Kahuku may be considered to be a principal factor in the regional distribution of index constituents with a relatively uniform nitrate distribution throughout. Local effects of pumping are quite pronounced and influence overall increases of indices, indicating that where heavy pumping takes place for irrigation, the increase in index constituents are correspondingly greater.
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    WRRCTR No. 45 Density Logs from Underground Gravity Surveys in Hawaii
    (Water Resources Research Center, University of Hawaii at Manoa, 1971-02) Huber, Richie D. ; Adams, William M.
    The gravity method has been applied in three wells in Hawaii to estimate density and porosity logs. The wells are the Schofield shaft on the island of Oahu, the Kihei #3 shaft on the island of Maui and the Pahala shaft on the island of Hawaii. The method determines the "averaged" density and porosity values for Hawaiian rocks. On Oahu, the density at depth is 2.4 gm/cc and the corresponding porosity is 18 percent. For Maui, the density averages about 2.4 gm/cc and porosity at 17 percent. The Hawaii shaft shows a lower density of 2.0 gm/cc with a correspondingly higher porosity of 27 percent. All these values are based on a grain density of 2.9 gm/cc.
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    WRRCTR No. 4 Development of Deep Monitoring Stations in the Pearl Harbor Ground Water Area, Oahu
    (Water Resources Research Center, University of Hawaii at Manoa, 1967-03) Cox, Doak C. ; Lao, Chester
    Two deep wells, one at Puuloa and the other at Ewa Beach in the Pearl Harbor area were drilled through the thick sedimentary gap into Koolau basalt, and have been readied for multiple-zone recording of water levels and water quality. Plastic pipes were lowered into the wells to selected depths determined by core composition and electric well logs. Gravel and beach sand were used selectively to backfill the wells. Thirteen sampling tubes were installed in the Puuloa well, and seven sampling points were placed in the main well at Ewa Beach. A shallow auxiliary well was also drilled at Ewa Beach. Evidence from preliminary development of the deep aquifer at Ewa Beach indicates the possible existence of a thin layer of fresher water floating on water of nearly seawater composition. Water levels are being monitored in this aquifer and show a tidal efficiency of approximately 15 percent. The smaller sampling tubes are being developed at both sites.
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    WRRCTR No. 3 Dynamic and Static Studies of Seawater Intrusion
    (Water Resources Research Center, University of Hawaii at Manoa, 1967-02) Lau, L. Stephen
    A theoretical equation was adapted and modified for a water-table aquifer to relate freshwater flow to the sea, geometry of the fresh water-sea water interface, and aquifer characteristics under dynamic equilibrium. Verification was obtained in laboratory experiments conducted in a hydraulic sand model. Other laboratory experiments revealed special flow patterns in the transitional zone of the freshwater-seawater interface. The extent and the vertical density gradient of the brackish water in the transitional zone were examined for their effects on modifying the conventional Ghyben-Herzberg Patio. Groundwater data collected from a deep well on Oahu, Hawaii was discussed as an illustration.
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    WRRCTR No.2 Infiltration and Percolation of Sewage Through Oahu Soils in Simulated Cesspool Lysimeters
    (Water Resources Research Center, University of Hawaii at Manoa, 1966-08) Koizumi, Melvin K. ; Burbank, Nathan C. ; Lau, L. Stephen
    This study investigated conditions contributing to cesspool failure and followed selected parameters to measure the degree of treatment afforded sewage in cesspool disposal. This laboratory study utilized bench scale soil lysimeters and two basic soil types: the Wahiawa Low Humic Latosol and the Lolekaa Humic Latosol. The soils were specimens from areas of potential urban development within known ground water recharge zones. The results of this experiment indicate that unless further degradation of the effluent is effected by the soil mass, the incomplete degradation of the sewage makes it a definite hazard to ground water sources. This study presents soil-effluent inter-reaction at a one-foot depth. No conclusive evidence exists to substantiate any further degradation of the effluent by the soil at greater depths to the required U.S. Drinking Water Standards of 45 mg/l of nitrates.
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    WRRCTR No.81 A Dynamic Water and Related Land Resource Planning Model: It's Application to an Hawaiian Small Water System
    (Water Resources Research Center, University of Hawaii at Manoa, 1974-07) Liang, Tung ; Huang, Wen-Yuan ; Wu, I-Pai
    Planning an optimal system of activities for generating economic goods and services within an existing natural resource capacity is a difficult problem to solve. A mathematical programming model with the capacity to check multiple resource demand and supply compatibility over many time periods was developed as a solution to this type of problem. The characteristics of natural resource supply and the demand of activities were utilized to reduce the number of time periods and to minimize the loss of the dynamic reality of the problem. Reduction in the number of time periods extended the capability of the model in solving complex resource planning problems without oversimplification. The advance in computer memory size and speed has made multi-period mathematical programming models a practical and desirable tool in planning optimal production scheduling and optimal allocation of resources. However, the construction of a large constraint matrix generated by multi-period models remains an obstacle to the use of multi-period linear programming (LP) models. A matrix generator capable of dividing time span according to resource characteristics and TBM-MPS output compatible matrix for LP optimization was developed.
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    WRRCTR No.79 Water Recycling of Sewage Effluent by Irrigation: A Field Study on Oahu: Second Progress Report for July 1972 to July 1973
    (Water Resources Research Center, University of Hawaii at Manoa, 1974-11) Lau, L. Stephen ; Ekern, Paul C. ; Loh, Philip C.S. ; Young, Reginald H.F. ; Burbank, Nathan C Jr. ; Dugan, Gordon L.
    An investigation of recycling sewage effluent by irrigation under Hawaiian conditions is being conducted in pilot field studies near Mililani Town in central Oahu under the sponsorship of the Board of Water Supply and the Division of Sewers, City and County of Honolulu. The primary objective of the project is to determine the feasibility of wastewater application to the soil and its probable effects on the quality of groundwater in terms of dissolved materials and viruses. Corollary objectives are to ascertain its effects on sugarcane yield and grasslands.
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    WRRCTR No.82 Fate of Heavy Metals in the Sewage Treatment Process
    (Water Resources Research Center, University of Hawaii at Manoa, 1974-09) Nomura, Myron M. ; Young, Reginald H.F.
    Heavy metals have long been known to exert toxic effects upon plants and animals at all trophic levels. Through the use of water as a cleansing and transporting agent, various types and forms of metals find their way into the sewerage system. To determine the fate of heavy metals sewage treatment processes, a study covering a period of five months was conducted at the Wahiawa Sewage Treatment Plant. The study involved determining the distribution of metals in the various fractions of the wastewater and sludges in addition to the overall removed in the system. The step-aeration activated sludge treatment process, employed at Wahiawa, removed most of the heavy metals, Al, Cd, Cu, Fe, Hg, Pb, and Zn, that were detected at the plant in concentrations ranging from a few parts per billion of mercury to a few parts per million of iron. Hexavalent chromium was removed somewhat less efficiently and nickel was reduced in concentration only slightly compared to the other metals monitored. Results of this investigation showed that most of these metals were removed by precipitation with the sludges in primary treatment and further removal occurred through biological uptake in the secondary phase of treatment. The residual concentrations of metals in the final effluent discharge were usually below toxic levels, with the exception of nickel, for freshwater aquatic organisms and plants.
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