The state Water Commission has issued its third decision in a decade on how to allocate water from the Waiahole Ditch. Once again, the decision leaves many water users on both sides of the Ko'olau Mountains frustrated — though for different reasons.

The latest decision divides 27 million gallons a day of water generally along the same lines as in its previous efforts, with roughly equal amounts going into the Windward O'ahu watershed and to the agricultural fields of Central O'ahu.

A remnant, 2.43 million gallons a day, is being left in Windward streams until there's a Central O'ahu use for it.

That remnant, which is termed "unpermitted water" in the Commission on Water Resources Management report, is the focus of much of the early controversy over this ruling. Central O'ahu vegetable farmer Larry Jefts said a reserve is a good idea, particularly since the needs of agriculture can change dramatically, depending on the crop.

"I think we don't know what the future is, and I always thought it was OK that the commission leaves a little in limbo," Jefts said.

Two members of the water panel issued a dissenting opinion. State Land Board Chairman Peter Young and state Health Director Chiyome Fukino argued that the commission's allocation of the ditch's flow fails to meet the standards set by the Hawai'i Supreme Court in 2004.

"The message I heard from the Supreme Court is, we need to do things differently," Young said yesterday.

Waiahole Ditch, with its 2.7-mile tunnel through the Ko'olaus, was opened 90 years ago to irrigate sugar fields. It draws water from four major Windward streams and from the mountain water sources that feed the streams. The system was expanded 75 years ago and again 40 years ago, and now carries millions of gallons daily of cool water to Central O'ahu. The ditch runs 25 miles from Kahana to Honouliuli.

A generation ago, Windward taro farmers and others began arguing that some or all of that water ought to be returned to Waiahole, Waianu, Waikane and Kahana streams. The Water Commission in 1997 and 2001 made water allocations that distribute some of the flows back to the streams, and twice those allocations have been successfully challenged before the state Supreme Court.

Taro farmer Charlie Reppun, who has been active in the battle from the beginning, said the allocation hasn't been enough, and that there is significant value to having full, cold, deep streams.

"They say we've satisfied all the criteria for how much water you need to leave in the stream, but I don't think they recognize the value of big streams," he said.

Young said large streams create estuaries that are important for marine life, support healthy stream life, support streamside agriculture like taro, and have scenic and other values. In his seven-page dissent from the majority ruling, he wrote: "I diverge from the majority's view that the unpermitted remainder is to be left in the streams as some commodity awaiting future permitting to some off-stream use."

The Water Commission's division goes this way: 12.57 million gallons a day go to water users with permits in Central O'ahu, of which the Estate of James Campbell is the largest; 12 million gallons a day are to be restored to streams (4.8 million to Waiahole, 3 million to Waianu, 2.1 million to Waikane and 2.1 million to Kahana); and the remnant 2.43 million gallons of water would be returned to streams until a Central O'ahu permit is issued.

The 12 million gallons allocated to the streams is established as the minimum flow needed to support the streams' vital functions — what planners call the in-stream flow standard. That use ought to be the highest priority for the commission, said Earthjustice attorney Kapua Sproat, who represents Windward interests, including Hakipu'u 'Ohana, Ka Lahui Hawai'i, Kahalu'u Neighborhood Board and Makawai Stream Restoration Alliance.

"Our state Water Code mandates that this commission restore streams where practicable, not treat our public-trust resources as convenient reservoirs for speculators who are banking their land for future development," Sproat said.

The Campbell Estate's extensive Central O'ahu holdings are allocated nearly a third of the water flowing to Central O'ahu. Campbell Estate vice president Dave Rae said the estate had not seen the water ruling and could not comment on it.

Young and Fukino, in their dissent, suggested the Water Commission should have more carefully studied some of the holders of water permits — notably the continued allocation of 750,000 gallons per day to the Pu'u Makakilo golf course project that was never developed and appears unlikely to be developed.

Robert Creps, senior vice president of the real-estate holding company Pu'u Makakilo, said the turmoil over water allocations has made it difficult to plan.

"We've been given the allocation three times by the commission, and it's been taken away twice by the Supreme Court. Here we go again," Creps said.

Will Pu'u Makakilo keep its allocation? "We're looking at that. We're evaluating it," he said.

Young and Fukino argued that the firm be asked to make a case before the Water Commission for why it should get the water allocation.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.