Evaluation of major dike-impounded ground-water reservoirs, island of Oahu

Abstract

"Ground-water reservoirs on Oahu store a very large but only approximately estimatable quantity of freshwater. These reservoirs include interconnected water bodies that are impounded by volcanic dikes or other geologic structures, and water bodies that are floating on saline ground water in dike-free Java flows in the flanks of the volcanoes. A significant amount of water is stored above sea level, to an altitude of at least 2,000 feet in the Waianae Range, but most is stored below sea level. The depths of freshwater storage below sea level range from a few feet to 1,000 feet or more in the dike-free lavas, and probably to several thousands of feet in the compartmented lavas between dikes. Other water bodies, smalI in comparison, are perched above and isolated from these interconnected bodies. "This report is primarily concerned with high-head dike-impounded ground-water reservoirs that underlie interior mountainous areas where rainfall and subsequent recharge to ground water are the greatest. These reservoirs, owing to their upgradient positions, play a very important role in the recharge, storage, movement, and discharge of alI ground water on the island."

Includes bibliographical references (p. 135-139).

Prepared in cooperation with the Board of Water Supply, City and County of Honolulu.