Iao Aquifer – Already Maxed Out

Prepared by James Williamson: BCE, FASCE, PE(ret):6/6/07

Potable water supply for central and south Maui, and Paia, comes from the Iao Aquifer, which has been under stress for some time. Demand on this aquifer on an annual average basis, is now about 18 mgd (million gallons per day). United States Geological Survey data obtained shows. total pumping demand increased by about 100% over the last 20 years. Corresponding well levels are 50% less. Pumping has increased from some 17 mgd over the last five years and is currently at its safe sustainable yield.

Hence a further increase in demand is unsafe. The South Maui population in addition is supplied by 4 – 5 mgd   from the Waihee aquifer which is also at its limit. Thanks to the Maui Meadows Homeowners Association, Iao is now designated for state control but that has not happened for the Waihee aquifer. In all potable water supplies for South Maui (including Maui Meadows) are not firm.

An additional water source(s) for South Maui’s water supply should be researched,investigated and proven up. In the past we have suggested additional wells in the vicinity of Kahakuloa. We believe the county should examine this possibility in detail. We are sure there are other alternatives and the county has a budget to investigate them. If the Wailea 670 developer drills wells for its project they should be proven up and dedicated to the county in accordance with the Public Trust Doctrine, before further zoning approvals are given.