On May 20, the state Commission on Water Resource Management voted unanimously to accept a petition by the Honolulu Board of Water Supply to designate the Waiʻanae aquifer sector as a ground water management area.
The area incudes the aquifers for Nānākuli, Lualualei, Makaha, Waiʻanae, and Keaʻau, and is the only sector on Oʻahu not yet designated.
In voting to approve the petition, commissioner Lawrence Miike questioned why the Waiʻanae sector had not already been designated, since demand as long exceeded the available supply, requiring the BWS to pump water in from the Pearl Harbor aquifer sector to meet about half of the sector’s needs.
Before the commission can vote to designate, a public hearings must be held, scientific information must be gathered to inform proposed findings of fact, and there must be further consultation with the May, City Council and BWS.
If and when the Water Commission votes to designate, existing and new users will then have to apply for water use permits.
At the Water Commission’s May 20 meeting, program administrator for the BWS Water Resources Division Barry Usagawa explained how reliant the sector is on outside water, as well as the limitations of developing more capacity both within and outside the Waiʻanae sector.
Before voting to accept the petition, the Water Commission approved a scope of work for the BWS’s Waianae Watershed Management Plan update, which will be part of the Oʻahu Water Use and Development Plan.
Usagawa explained that the watershed management plan will be prepared by its consultant, SSFM. The plan will include projections low, medium, and high of demand and supply through the year 2045, as required by ordinance.
“But that’s not enough … when you’re talking about sustainability,” he said.
“The rainfall forecasts, they’re all looking at a drying trend. … When you start to look forward far enough, you start to run out of water at some point, and when you start doing that, then it drives specific actions that we should be setting sooner than later. So taking that longer-term look allows us to spread that cost out and then devise alternatives and work out those problems.
So the plan will also include low and high projections to the year 2100. “It’s a low and high because [the University of Hawaiʻi] has a low and high forecast [that] contribute to amount to sustainable yield we’ll find in Waiʻanae,” he said.
The plan is expected to be complete in 2027. Should the Water Commission vote to designate the sector, as appears likely, it would be in the midst of considering water use permits for the area when the plan is done.
Commission chair Dawn Chang asked, “While we’re proceeding with our process, how do you see the integration with the planning process?”
“It’s complicated,” Usagawa replied. In applying for its water use permit, the BWS would seek an allocation that is “more tied to what the [sustainable] yields will be, not the demand. … We don’t want to be asking for more than what the wells can actually produce.”
With regard to the supply from the Pearl Harbor aquifer sector that Waiʻanae relies on, he noted that the Waipahu-Waiawa aquifer’s sustainable yield is 104 million gallons a day and only about 60 mgd is being pumped.
“There’s unused sustainable yield there that may be affected by climate change,” he said. The Ewa-Kunia aquifer sustainable yield, however, is predicted to decrease, he said.
With yields for Makaha and Waiʻanae also predicted to decrease, Usagawa suggested that bringing water in from outside is not a panacea.
Meeting demand with whatever what sustainable yields are set must take into account the BWS system’s limitation.
“We can’t get water all the way to Makaha. … If the straw is long enough, you can only blow so much. Nothing comes out the other end,” he said, adding that the system can only take Pearl Harbor aquifer water as far as Waiʻanae town.
Addressing more broadly of system capacity and development on the island, commissioner Hannah Springer asked whether, for the BWS, water availability may “come in line ahead of land use.”
“It seems like we investigate water resources after commitments to develop land have been made. Using my water sensibility hat, I’m not going to build a loʻi if there is no stream nearby. Are we inclined in that direction now?” she asked.
Usagawa replied that he looked at land use and water availability concurrently.
“They go hand-in-hand,” he said. “You cannot plan for the next big growth area until you know how much water we got. And we don’t know how much water … we’ll need in our system capacity. We can’t plan for expanding that until we know how much the growth is. It’s chicken and egg, but it’s concurrent.”
He added that he hoped developers “have the wherewithal to at least ask us what is it going to take and we can comment on a land use plan.”
“This whole climate change layer and potential reducing of the sustainable yield of the aquifers because rainfall is decreasing, we have already told some of the large transit-oriented developments that we cannot confirm all the water you’re projecting. So then it’s a first come, first served, on our system on the remaining amount.”
He said the shutting down of wells as a result of contamination from the U.S. Navy’s Red Hill fuel tanks exacerbates the problem. “Now there’s less for ʻEwa and Waiʻanae, if you start to reduce sustainable yield, you start to get to the point we don’t have the capacity. It’s thin now,” he said.
“We’re trying to support growth but [developers] have to have an idea of how much water got. Otherwise, we’ll just say, ’Not yet,’” he said.
— Teresa Dawson
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