More than 14 million gallons of water is pumped from North Kona’s Keauhou aquifer every day on average. And even with water use increasing 19% over the past decade as the region’s population grows, there’s room to pump more, state data shows.

Developers are eager to tap into the resource and build new wells as others urge caution and call for tighter restrictions. Concerns are growing over environmental degradation and declining rainfall amid a changing climate.

The state Commission on Water Resource Management is playing referee, implementing an adaptive management plan for the aquifer to better inform groundwater permitting and pumping decisions and improve monitoring. 

Daily pumpage is still well below the aquifer’s sustainable yield, the maximum rate at which water can be withdrawn without impairing the utility or quality of the source. The state has determined that 38 million gallons can be pumped per day from the Keauhou aquifer, with current usage at just 37% of the sustainable yield. 

Hawaiʻi County’s Department of Water Supply is allowed to use 61% of the permitted water withdrawal from Keauhou aquifer. That’s the maximum amount of water a well owner can use but does not mean they’re using all that’s allowed.

Most of the water used by the county — 53% — is for domestic use, according to a 2017 report. Municipal use, which goes to schools and various commercial, government, medical and nonprofit entities, accounted for 31% of water use. Some 14% was used for agriculture.

The next largest users are wells on land owned by Kohanaiki Shores and Kona Country Club, private luxury communities and clubs which use a large portion of the water for golf courses and ground irrigation.

Golf courses account for 9% of permitted water use, the second largest sector after the county, not including unused wells. Geothermal plants use about 2%.

A New Plan

State water commissioners say there should be a new approach to better understand how much water can be pumped without affecting the aquifer and environment, especially as studies show the amount of groundwater that replenishes the aquifer could decrease significantly as climate change affects rainfall.

The availability of groundwater is dependent on recharge, or the replenishment of fresh groundwater, and ground and surface water interactions.

The Keauhou aquifer could see its recharge decrease between 22 million and 53 million gallons per day, a 21% to 53% difference from a 101 million gallons per day baseline, a 2024 United States Geological Survey study found.

Worries over growing water demand and its impact on the ecosystem led the National Park Service to petition the state water commission to designate the aquifer as a groundwater management area in 2013. That would have given the groundwater special protection and required approvals to proposed wells. 

That designation was opposed by developers and then-Mayor Harry Kim. After years of debate, the state water commission ruled in 2017 that the aquifer did not meet standards for the designation. 

Last year, the commission decided to take a different approach — a first-generation adaptive management plan. The Legislature passed two bills in 2025 that provide a combined $4.2 million to build two deep monitor wells and require reports every six months detailing groundwater levels and the aquifer’s water quality. 

The adaptive plan’s goal is to ensure the flow of fresh groundwater is sufficient to native ecosystems and public trust obligations to Native Hawaiians and direct decisions regarding future wells and groundwater uses. It will establish a monitoring program and create a plan to learn about the aquifer system for future management methods. 

The commission is also looking to reevaluate the sustainable yield and create separate rules for the different aquifer bodies. The Keauhou aquifer consists of at least three bodies: a basal lens, a high-level aquifer body and a deep confined body. Most water in North Kona is pumped from the basal lens, a layer of freshwater near the shore. 

But water commissioners worried that without the ability to regulate withdrawals and new wells under an official designation, there was little the commission could do to protect the aquifer. 

Information is great, commissioner Lawrence Miike said in an August presentation of the adaptive management plan. But the commission’s control over sustainable yield will be limited if there’s no control over well construction and pump permits.

“Data Dive” is supported in part by the Will J. Reid Foundation. Civil Beat’s coverage of environmental issues on Hawaiʻi island is supported in part by a grant from the Dorrance Family Foundation; coverage of climate change and the environment is supported by The Healy Foundation, the Marisla Fund of the Hawai‘i Community Foundation and the Frost Family Foundation.