Pacific Islands Water Science Center
Recent hydrologic conditions, Iao and Waihee aquifer areas, Maui, Hawaii
Data provided by the State of Hawaii Commission on Water Resource Management, the Hawaii State Climate Office at the University of Hawaii at Manoa Meteorology Department, Maui Land and Pineapple Company, Inc., and the National Weather Service.
The Iao and Waihee aquifer areas have a dramatic range in rainfall between Puu Kukui (altitude 5,788 ft) and the shoreline. The mean annual rainfall at Puu Kukui (about 370 in.) is the second highest recorded in the State. Mean annual rainfall declines rapidly toward the ocean and is 30 in. or less at the shoreline. Precipitation in the area is actually a combination of rainfall over all elevations and fog drip at higher elevations where the montane forest canopy intercepts cloud water. Fog drip studies of mountains in Hawaii have shown that fog drip can significantly augment rainfall at elevations above 2,000 ft (US Geological Survey Water-Resources Investigations Report 00-4223).
Three rainfall stations are reported here. Station 380, Puu Kukui, at an altitude of 5,790 ft, includes rainfall data collected since 1928. Station 482, Waihee Valley, at an altitude of 300 ft, includes data collected since 1913. Station 484, Waiehu Camp, at an altitude of 320 ft, includes data collected since 1910.
Summary of recent conditions
Rain-gage data are current through July 2010 at Puu Kukui rain gage and May 2010 at Waihee Valley and Waiehu Camp rain gages. The 12-month moving mean increased at the Puu Kukui rain gage and decreased at the Waiehu Camp and Waihee Valley rain gages but the 12-month moving means of rainfall are below the long-term means at all three gages.
At Puu Kukui, the 12-month moving mean through July 2010 is about 57 percent (209 in) of the long-term mean (367 in/yr).
At Waiehu Camp, the 12-month moving mean through May 2010 is about 88 percent (31 in) of the long-term mean (35 in/yr).
At Waihee Valley, the 12-month moving mean through May 2010 is about 90 percent (41 in) of the long-term mean (45 in/yr).
Additional information about the Iao aquifer area can be found in:
"Ground-water availability in the Wailuku Area, Maui, Hawai'i" by Stephen B. Gingerich, 2008, US Geological Survey Scientific Investigations Report 2008-5236
"The response of the Iao aquifer to groundwater development, rainfall, and land-use practices between 1940 and 1998, Island of Maui, Hawaii" by William Meyer and Todd K. Presley, 2001, US Geological Survey Water-Resources Investigations Report 00-4223
"Analytical versus numerical estimates of water-level declines caused by pumping, and a case study of the Iao aquifer, Maui, Hawaii" by Delwyn S. Oki and William Meyer, 2001, US Geological Survey Water-Resources Investigations Report 00-4244
Twelve-month moving mean of rainfall at Puu Kukui, Waihee Valley, and Waiehu Camp rain gages, 1985 to present.
Monthly rainfall at Puu Kukui, Waihee Valley, and Waiehu Camp rain gages, 2009 to present.