Need for Accurate Need for Accurate Horizontal and Vertical Horizontal and Vertical Datum for Datum for Groundwater-Resource Groundwater-Resource Assessments in Hawaii Assessments in Hawaii and the Pacificand the Pacific

Stephen AnthonyStephen AnthonyU.S. Geological SurveyU.S. Geological SurveyPacific Islands Water Science Pacific Islands Water Science CenterCenterHonolulu, HawaiiHonolulu, Hawaii

U.S. Department of the InteriorU.S. Geological Survey

USGS Water MissionUSGS 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 Partnerships with Federal, State and Local Agencies in Hawaii and the Local Agencies in Hawaii and the

PacificPacific

• 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

NeedNeed for Accurate Vertical and Horizontal for Accurate Vertical and Horizontal DatumDatum

• 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, OahuFreshwater Lens, Pearl Harbor, Oahu

Pearl Harbor Area Groundwater Levels, Pearl Harbor Area Groundwater Levels,

20032003

Priority Areas Requiring Periodic Priority Areas Requiring Periodic Updates of Vertical & Horizontal Updates of Vertical & Horizontal

DatumDatum

• 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