{"id":145706,"date":"2021-07-29T15:58:58","date_gmt":"2021-07-30T01:58:58","guid":{"rendered":"https:\/\/www.hawaii.edu\/news\/?p=145706"},"modified":"2021-08-05T08:46:38","modified_gmt":"2021-08-05T18:46:38","slug":"main-oahu-aquifer","status":"publish","type":"post","link":"https:\/\/www.hawaii.edu\/news\/2021\/07\/29\/main-oahu-aquifer\/","title":{"rendered":"Sustainable water withdrawal from main O\u02bbahu aquifer may decrease"},"content":{"rendered":"Reading time: <\/span> 3<\/span> minutes<\/span><\/span>
\"swampland
Pearl Harbor Wildlife Sanctuary<\/figcaption><\/figure>\n

The future of Oʻahu<\/span>\u2019s primary water source may be in jeopardy if current water withdrawal rules remain unchanged. According to University of Â鶹´«Ã½<\/span> at M\u0101noa researchers, the current sustainable yield (the maximum rate that water can be withdrawn from aquifers without compromising human and ecological uses) estimate for the Puʻuloa<\/span> (Pearl Harbor) aquifer at 182 million gallons per day (MGD<\/abbr>) could be a large over-estimate and may need to be reconsidered.<\/p>\n

Even without considering climate and land-use change, the UH<\/abbr> research team estimates sustainable yield at 151 MGD<\/abbr>, which could decrease to 113 MGD<\/abbr> by mid-century under a dry future climate scenario (set by the Intergovernmental Panel on Climate Change) combined with further urban sprawl and watershed degradation.<\/p>\n

Withdrawing too much water from the aquifer will not only impact the island\u2019s drinking water source, but would also negatively impact culturally and ecologically important springs that feed areas such as the Sumida Watercress Farm, loʻi<\/span> kalo systems, coastal wetlands and nearshore ecosystems. Adequately protecting springs and submarine groundwater discharge will require reducing sustainable yield estimates even further.<\/p>\n

A team from the University of Â鶹´«Ã½<\/span> Economic Research Organization<\/a> (UHERO<\/abbr>) in the College of Social Sciences<\/a>, the Water Resources Research Center<\/a> (WRRC<\/abbr>), the Â鶹´«Ã½<\/span> Institute of Geophysics and Planetology<\/a>, Pacific RISA<\/abbr><\/a> and the National Science Foundation-funded ʻIke<\/span> Wai project<\/a> at UH<\/abbr> said this research shows the amount of water that can be safely withdrawn from the Puʻuloa<\/span> aquifer in the future may be significantly less because climate change is expected to reduce rainfall, the source of fresh water to the aquifer. They also say “protecting mauka watersheds from high-water-use invasive tree species, which can further reduce groundwater recharge, is critical in the face of such change.”<\/p>\n

Sustainable yield limits<\/h2>\n
\"forests
The ʻEwa<\/span> Forest Reserve is where the Koʻolau<\/span> Mountains Watershed Partnership is working to protect native forests, and researchers found that could provide water benefits over the long-term.<\/figcaption><\/figure>\n

The UH<\/abbr> M\u0101noa researchers acknowledged that Â鶹´«Ã½<\/span> has among the most progressive water laws, which is rooted in Indigeneous management principles. However, accuracy of the current estimates is limited due to the lack of comprehensive data and shortcomings of the model (the Robust Analytical Model 2) used by the State to determine sustainable yield limits. The research team said such a model is a “bathtub” type that ignores the spatial distribution of various inflows and outflows including well withdrawals, and does not directly consider some public trust uses (for example, maintenance of waters in their natural state and exercise of Native Hawaiian traditional and customary rights) or climate and land-use change.<\/p>\n

Puʻuloa<\/span> aquifer<\/h2>\n

To assist in developing a more comprehensive analysis, the research team conducted two related studies on the Puʻuloa<\/span> aquifer, which provides two-thirds of Oʻahu<\/span>\u2019s drinking water.<\/p>\n