Thesis (M.S.)--University of Hawaii at Manoa, 2007. / Includes bibliographical references (leaves 18-20). / vii, 20 leaves, bound col. ill. 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 98-106). / vii, 106 leaves, bound 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 42-47). / viii, 64 leaves, bound 29 cm

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 103-108). / xiv, 108 leaves, bound ill. 29 cm

Thesis (M.A.)--University of Hawaii at Manoa, 2007 / Pacific Islands Studies

Thesis (M.A.)--University of Hawaii at Manoa, 2003 / Pacific Islands Studies

Thesis (M.A.)--University of Hawaii at Manoa, 1997 / Pacific Islands Studies

Thesis (M.A.)--University of Hawaii at Manoa, 1982 / Pacific Islands Studies

Twenty-one Schlumberger resistivity soundings were performed on the island of Maui. Analysis consisted of one-dimensional modeling using an automatic ridge-regression inversion algorithm (Anderson, 1979). The inversion results were compared with available well-log information and geologic maps in order to make geologic interpretations. The soundings were conducted primarily to estimate the depth to and the electrical resistivity of, seawater-saturated basalt for different parts of the island. The resistivity of seawater-saturated basalt on Maui ranges between 3.5 and 60 ohm-meters. The lowest values occurred near Ukumehame canyon, on the south rift zone of West Maui. In this area, which is the site of a warm water (33°C) well, the computed resistivity for seawater-saturated basalt is about 4 ohm-m. Using typical Hawaiian basalt porosity values of 15% to 25%, Archie's Law implies temperatures of between 62° and l7loC at depths below 200 meters in the Ukumehame area. Freshwater piezometric heads were estimated from the sounding data. The largest freshwater head (91 m) was obtained in Keanae valley. The inferred large volume of freshwater is perched on Keanae alluvial valley fill and is observed in a well (W100) towards the back of the valley. All other freshwater heads are under 4 m, indicating that the freshwater lens is rather thin near the coast at the areas surveyed. / ill / maps

Groundwater contamination caused by agricultural fertilization is a widely recognized problem. In Hawaii, nitrogen fertilization from pineapple and sugarcane fields has posed a threat to several basal aquifers and has been implicated in coastal algae blooms. The concentration of nitrate-N in the Pearl Harbor basin on the island of Oahu was below 2.3 mg/L in the 1950’s and 1960’s, and has increased to as much as 7.6 mg/L in 1992 to 1994. The objective of this dissertation research is to develop a practical methodology for realistically estimating nitrate leaching from fertilized agricultural lands. Numerous mechanisms have impact on the distribution and migration of nitrate in the soil. Nitrogen fertilizer undergoes many N transformations and interactions with the soil and the plant after applications. In this study, an analysis of soil samples was performed to understand the leaching process of nitrate in the root zone of three different cropped fields in Hawaii. A detailed discussion is given to address various factors which control the nitrate transport process. To judge the sampling plan in relation to spatial variation, the field measurements were evaluated statistically by an uncertainty index, which is represented as the density of samples required for the estimate of sample mean of the nitrate concentration to fall within a defined limit of accuracy. In order to predict the effect of nitrogen fertilization on the groundwater contamination with very limited input data, a simple, analytical, lumped parameter model (LPM), was developed. The model can estimate the average nitrate leaching from the root zone in response to agricultural practices, N transformations and other related processes. The model was tested against the field data and two detailed numerical models, LEACHM-N and CERES-Maize. It provides an alternative way to assess nitrate leaching from the root zone with acceptable accuracy. A listing of the program is provided in Appendix 2. Owing to the complex nature of nitrogen behavior in the unsaturated zone, some degree of uncertainty is involved in the development of modeling approaches. In this study, five major sources of uncertainty were identified. These are: uncertainty due to spatial variation, uncertainty related to the accuracy of the input data, uncertainty due to simplifications in the development of the models, uncertainty due to the modeling parameters, and uncertainty due to the complexity of the unsaturated zone in Hawaii. The impact of these uncertainties on simulation results is evaluated. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1996. / Includes bibliographical references (leaves 202-215). / UHM: Has both book and microform. / Water Resources Research Center, University of Hawaii at Manoa