Is There Enough Water for South Maui?

Is There Enough Water for South Maui?

By John Laney 09/02/2026 #kca #water

South Maui is standing at the edge of a major transformation. Wailea 670, Makena Mauka, and the Ledcor project are all positioned to begin construction, representing roughly 3,500 new homes in the near term and thousands more in the pipeline. These developments have been discussed for years, debated for years, and planned for years. Now they are much closer to moving dirt.

But an important question sits at the center of everything: Is there enough water for South Maui?

This is not a rhetorical question. It is not an abstract planning question. Today, according to the Department of Water Supply, South Maui’s potable water system is operating at roughly 98% capacity. That number alone should give us pause. It means we are essentially running our water system at full throttle, with no margin for drought, well failures, infrastructure issues, or unexpected demand. It also means that any new development must be evaluated with extraordinary care.

Yet the Makena Mauka and Wailea 670 developments now preparing to build are proposing a solution that raises as many questions as it answers: reverse osmosis (RO) desalination plants.

RO systems are not new. They are used around the world, and they can produce high‑quality potable water. But they come with significant challenges that South Maui must confront honestly before we allow thousands of new homes to rely on them.

The Energy Question

Reverse osmosis is energy‑intensive. Modern RO systems are more efficient than older ones, but they still require substantial electricity to push seawater or brackish water through membranes at high pressure. For a development like Wailea 670, which anticipates needing roughly half a million gallons per day, the energy demand can be enormous.

Where will that energy come from? Will developers build renewable energy systems to support their RO plants? Will they rely on the grid? If so, what does that mean for Maui Electric’s already strained infrastructure? And what happens during outages, brownouts, or storm events? And, can it end up causing HECO to raise our rates? 

One simple solution is to REQUIRE any desalination or RO plants to use Solar. You don’t strain the grid, you don’t cause higher demand to increase rates. Currently, there is no requirement that major new developments use solar.

Governor David Ige signed  House Bill 623 into law in 2015, establishing Hawaiʻi’s requirement that electric utilities reach 100% renewable net electricity generation by December 31, 2045. Let’s begin now to assist in moving the needle to renewable net electricity generation by requiring all Desalination Plants to use Solar with Battery Back-up for redundancy now!

The Brine Question

Every gallon of fresh (potable) water produced by RO leaves behind approximately a gallon of concentrated brine — water that is roughly twice as salty as the ocean. That brine must go somewhere.

Will these developers build infrastructure to dilute their brine (having to use more brackish water) and use it for irrigation, If so, what are the long‑term impacts on groundwater and aquifer health? Will it be discharged into the ocean? If so, how will it be diluted, and what will be the impact on coral reefs already stressed by sedimentation, warming, and wastewater? Will it be trucked, evaporated, or treated in some other way? Or will they use established, proven guidelines to discard their brine in deep injection wells?

Makena Mauka testified under oath their plan is to use the diluted irrigation method to dispose of the brine. Does that sound like a good plan? Using irrigation as a brine disposal method may look convenient in the short term, but it risks long‑term soil and groundwater damage potentially contaminating our ground water aquifer, the Kama’ole Aquifer. Brine may contain pretreatment or cleaning chemicals, including disinfectants, acids, antiscalants, coagulants, metals, and membrane-cleaning waste. These substances may create impacts beyond salinity alone.

Maui County’s 2024 desalination feasibility study evaluated brine reuse (diluted irrigation) for salt-tolerant turf and concluded that it was not recommended because of brine water quality, instead recommending deep-well disposal subject to hydrogeologic review and permitting. Before South Maui accepts thousands of new homes dependent on RO, we need a brine management plan that is scientifically sound, fully permitted, and protective of our aquifers and reefs—not a workaround that pushes today’s problem into tomorrow’s environment.

Brine disposal is one of the most challenging environmental issues associated with desalination. It cannot be hand‑waved away with assurances that “it will be handled.” South Maui deserves clear, transparent, science‑based answers.

The Aquifer Question

Developers plan to use wells tapping the Kama‘ole Aquifer. But we do not yet have a complete picture of that aquifer’s structure, recharge rates, or long‑term sustainable yield. That is why many in the community — including KCA — have called for Airborne Electromagnetic Imaging (AEM) and for the Ground Water Management Area (GWMA) designation.

If we are going to add thousands of new homes, we must know exactly what our aquifer can support. Guesswork is not stewardship.

The Community Question

South Maui residents already live with water restrictions. We already see the impacts of limited infrastructure. We already understand what it means to live at the edge of capacity. So before we add 3,500 plus new homes — and before we add the next 3,500 after that — we must ask: What is the plan? Not the conceptual plan. Not the “we’ll figure it out” plan. The real plan.

How will water be produced? How will it be delivered? How will it be stored? How will it be powered? How will it be regulated? And how will we be protected?

A Call for Transparency and Responsibility

KCA is not anti‑housing. We are not anti‑development. We are for SMART planning. We are pro‑environmental stewardship. We are pro‑community. We simply want to know that when thousands of new homes rise in our region, they will be supported by a water system that is safe, reliable, sustainable, and environmentally sound. Before construction begins, the County and developers must provide clear, public answers to the energy, brine, aquifer, and capacity questions. South Maui deserves nothing less.

Because the real question is not whether we can build 3,500 new homes.

The real question is whether we can sustain them. And that answer depends in large part on water!