GEOHYDROLOGY OF THE ISLAND OF OAHU, HAWAII Kauai HAWAII Niihau Molokai Oahu Maul Lanai Kahoolawe Hawaii PROFESSIONAL PAPER 1412-B ZUSGS science fora changing world AVAILABILITY OF BOOKS AND MAPS OF THE US. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current- year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publica­ tions released prior to the current year are listed in the most recent annual "Price and Availability List." Publications that may be listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" may be no longer available. Order U.S. Geological Survey publications by mail or over the counter from the offices given below. BY MAIL OVER THE COUNTER Books Books and Maps Professional Papers, Bulletins, Water-Supply Papers, Tech­ Books and maps of the U.S. Geological Survey are available niques of Water-Resources Investigations, Circulars, publications over the counter at the following U.S. Geological Survey Earth Sci­ of general interest (such as leaflets, pamphlets, booklets), single ence Information Centers (ESIC's), all of which are authorized copies of Preliminary Determination of Epicenters, and some mis­ agents of the Superintendent of Documents: cellaneous reports, including some of the foregoing series that have gone out of print at the Superintendent of Documents, are obtain­ ANCHORAGE, Alaska Rm. 101,4230 University Dr. able by mail from LAKEWOOD, Colorado Federal Center, Bldg. 810 U.S. Geological Survey, Information Services MENLO PARK, California Bldg. 3, Rm. 3128, 345 Box 25286, Federal Center, Denver, CO 80225 Middlefield Rd. RESTON, Virginia USGS National Center, Rm. 1C402, Subscriptions to Preliminary Determination of Epicenters can 12201 Sunrise Valley Dr. be obtained ONLY from the SALT LAKE CITY, Utah Federal Bldg., Rm. 8105, 125 Superintendent of Documents South State St. Government Printing Office SPOKANE, Washington U.S. Post Office Bldg., Rm. 135, Washington, DC 20402 West 904 Riverside Ave. WASHINGTON, D.C. Main Interior Bldg., Rm. 2650, 18th (Check or money order must be payable to Superintendent of Documents.) and C Sts., NW. Maps Only Maps Maps may be purchased over the counter at the following For maps, address mail orders to U.S. Geological Survey office: U.S. Geological Survey, Information Services Box 25286, Federal Center, Denver, CO 80225 ROLL A, Missouri 1400 Independence Rd. Geohydrology of the Island of Oahu, Hawaii By CHARLES D. HUNT, JR. REGIONAL AQUIFER-SYSTEM ANALYSIS OAHU, HAWAII U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1412-B U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Gordon P. Eaton, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government Library of Congress Cataloging in Publications Data Hunt, Charles D., Geohydrology of the island of Oahu, Hawaii / by Charles D. Hunt, Jr. p. cm. (Regional aquifer-system analysis Oahu, Hawaii) (U.S. Geological Survey professional paper ; 1412-B) Includes bibliographical references. Supt. of Docs, no.: 119.16 :1412-B 1. Geohydrology Hawaii Oahu. I. Title. II. Series III. Series: U.S. Geological Survey professional paper ; 1412-B. GB1025.H3H86 1996 551.49'09969'3-dc20 96-24418 CIP ISBN 0-607-86102-9 For sale by the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225 FOREWORD THE REGIONAL AQUIFER-SYSTEM ANALYSIS PROGRAM The Regional Aquifer-System Analysis (RASA) Program was started in 1978 following a congressional mandate to develop quantitative apprais­ als of the major ground-water systems of the United States. The RASA Program represents a systematic effort to study a number of the Nation's most important aquifer systems, which in aggregate underlie much of the country and which represent an important component of the Nation's total water supply. In general, the boundaries of these studies are identified by the hydrologic extent of each system and accordingly transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for each study is to assemble geologic, hydro- logic, and geochemical information, to analyze and develop an understand­ ing of the system, and to develop predictive capabilities that will contribute to the effective management of the system. The use of computer simulation is an important element of the RASA studies, both to develop an understand­ ing of the natural, undisturbed hydrologic system and the changes brought about in it by human activities, and to provide a means of predicting the regional effects of future pumping or other stresses. The final interpretive results of the RASA Program are presented in a series of U.S. Geological Survey Professional Papers that describe the geology, hydrology, and geochemistry of each regional aquifer system. Each study within the RASA Program is assigned a single Professional Paper number, and where the volume of interpretive material warrants, separate topical chapters that consider the principal elements of the investigation may be published. The series of RASA interpretive reports begins with Professional Paper 1400 and thereafter will continue in numerical sequence as the interpretive products of subsequent studies become available. Gordon P. Eaton Director CONTENTS Page Foreword........................................................................... III Geohydrology of the Water-Bearing Deposits Continued Abstract............................................................................ Bl Volcanic Rocks and Deposits Continued Introduction...................................................................... 2 Heterogeneity, Anisotropy, and Aquifer Structure... 25 Purpose and Scope...................................................... 2 Sedimentary Rocks........................................................... 25 Study Area.................................................................. 2 Modes of Ground-Water Occurrence..................................... 26 Physical Setting.......................................................... 2 Basal Ground Water......................................................... 26 Climate........................................................................ 4 Basal Water in the Volcanic Rocks............................ 27 Previous Studies......................................................... 5 Basal Water in the Sedimentary Rocks..................... 30 Geologic Framework........................................................ 7 High-Level Ground Water................................................ 31 Regional Geologic Setting.......................................... 7 Dike-Impounded Water.............................................. 31 Shield-Building Volcanism......................................... 8 Perched Ground Water and Water in the Shield-Stage Volcanic Rocks...................................... 9 Unsaturated Zone....................................................... 31 Waianae Volcanics................................................ 9 High-Level Water in the Schofield Area.................... 31 Koolau Basalt........................................................ 10 Saltwater.......................................................................... 31 Modification of the Shields by Secondary Processes. 10 Regional Aquifer System....................................................... 31 Subsidence and Slope Failure .............................. 10 Principal Volcanic-Rock Aquifers and Weathering and Erosion....................................... 10 Confining Units ............................................................... 32 Sedimentation....................................................... 11 Subordinate Aquifers....................................................... 32 Rejuvenated-Stage Volcanism.................................... 11 Geohydrologic Barriers and Ground-Water Areas ......... 32 Geohydrology of the Water-Bearing Deposits................. 11 Transient Hydraulic Behavior of the Volcanic Rocks and Deposits...................................... 12 Aquifer System................................................................. 37 Lava Flows............................................................. 12 Ground-Water Flow Systems ................................................ 41 Dikes...................................................................... 14 Rift Zones and the Eastern and Western Pyroclastic Deposits.............................................. 14 Ground-Water Systems.................................................... 43 Saprolite and Weathered Basalt.......................... 14 Central Flow System........................................................ 44 Hydraulic Properties of the Volcanic Rocks......... 16 Southeastern Flow System.............................................. 46 Hydraulic Conductivity and Transmissivity.. 16 Deep Saltwater Flow System........................................... 46 Porosity............................................................. 24 Summary................................................................................ 49 Specific Yield and Storage Coefficient............ 24 References.............................................................................