At the request of the Ulupono Initiative, Center for International Energy and Environmental Policy, Jackson School of Geosciences has studied Maui’s water availability.
A Systems Approach for Investigating Water, Energy, and Food Scenarios in East-Central Maui
concludes:
“The water availability for different scenarios is based upon the precipitation, surface water, and groundwater on the Eastern (Haleakala) portion of Maui. Most of the 330 million gallons per day (MGD) of average surface water runoff is already used for some purpose (see Figure E-1). While there appears to be a large amount of groundwater resource available, the costs are prohibitive for accessing the bulk of that water. Many new water supplies such as more pipelines, groundwater wells, reclaimed water facilities, and desalination are constrained by the available capital required to invest in new fresh and potable water sources. There is some opportunity to recover more wastewater that is already being reclaimed. Two strategies, (i) increased water conservation and demand management and (ii) increased wastewater treatment for reclaimed water use, have been determined to be the most promising options for matching Maui potable water demand with supply”
“in an average rainfall year, 30,000 acres of sugar cane in Central Maui cannot be sustainably fully irrigated….
Fully irrigating 23,000 acres of sugar cane (Scenario 2) provides approximately the same total biomass yield as the current practice of partially irrigating 30,000 acres (calibration scenario). Growing cassava and sweet sorghum requires much less water, although the assumption of less water for sweet sorghum corresponds to a relatively low yield for Hawaiian conditions. The 5,850 acres of pasture in Upcountry Maui for intense beef and milk production would require significant irrigation (5 BGY), assumed to come solely from groundwater. The irrigation requirements for 1,000 acres of diversified agriculture are minimal compared to the other crops.”
“Unfortunately, Hawaii’s future might be drier than its past. Rainfall has been experiencing a decreasing trend over the last several decades (see Figure 1), and if this trend continues, there can be significant negative consequences for the Hawaiian Islands”