Need for Accurate Horizontal and Vertical Datum for Groundwater- Resource Assessments in Hawaii and the Pacific Stephen Anthony U.S. Geological Survey Pacific Islands Water Science Center Honolulu, Hawaii U.S. Department of the Interior U.S. Geological Survey

USGS Water Mission Provide information to manage, protect, and enhance water resources Address water-related hazards Non-regulatory role Provide information that is reliable, impartial, and timely

Partnerships with Federal, State and Local Agencies in Hawaii and the Pacific Water-resource monitoring and assessment programs, FY 2011 –NPS, US Army, US Navy, US Marine Corps –Hawaii CWRM, SCD, DOH, DOT, DHHL, and OHA –County water and public works departments –University of Hawaii and University of Guam Reimbursable funding ~ $3.0 M per year USGS funding ~ $1.5 M per year

Need for Accurate Vertical and Horizontal Datum Groundwater provides more than 90% of the public water supply in Hawaii and Guam Water table of freshwater lens is extremely flat Potential errors in coastal areas can be high Resource assessments require accurate water level measurements referenced to common datum (mean sea level) –Determine groundwater flow directions and change in freshwater storage –Calibrate numerical groundwater flow models used to assess water availability

Freshwater Lens, Pearl Harbor, Oahu

Pearl Harbor Area Groundwater Levels, 2003

Priority Areas Requiring Periodic Updates of Vertical & Horizontal Datum Recently completed –Central Maui, 2003 –Lahaina, Maui, 2007 –West Hawaii Island, 2009 –Eastern Molokai, 2009 –Northern Guam, 2010 Current needs –Pearl Harbor area, Oahu, 2011