The Hawaii Supreme Court struck down on Wednesday a 2010 ruling by the state water commission, paving the way for more water to flow through a river and three streams on Maui.

The high court ruled that the Commission on Water Resource Management erred in ruling that the Wailuku Water Co. and Hawaiian Commercial and Sugar Co. must restore 12.5 million gallons of water a day that had been diverted from the river and streams.

The court said the commission must recalculate the amount of water to be restored to the river and streams.

Two Maui community groups — Hui O Na Wai Eha and the Maui Tomorrow Foundation — and the Office of Hawaiian Affairs challenged the commission’s ruling.

They contended the commission should have ordered more water to flow to allow for taro cultivation and the restoration of the natural habitat.

Isaac Moriwake, Earthjustice lawyer for the two community groups, called the high court’s ruling "a sweet victory."

He said the high court’s decision means that more water that had been diverted for the sugar industry will be restored.

"Our clients are in tears, tears of joy, but also tears of relief after so many years of frustration at the commission not following the law," Moriwake said.

Colette Machado, chairwoman of the OHA board of trustees, said the court’s ruling is a "long-overdue victory" and will have a "fair-reaching effect."

"The ruling shows agencies must protect natural resources that are critical not only to our immediate well-being, but to the very survival of our culture and way of life," she said.

But Rick Volner, Hawaiian Commercial general manager, said the commission’s 2010 ruling returned "substantial water" to the streams while giving the company "a fighting chance for survival."

He said based on his company’s preliminary review of the lengthy and complex ruling, it is "optimistic" that the commission will have more than an "adequate basis for its original conclusion" and will continue to "strike an appropriate balance" among the needs of the company, the community and stream uses.

In an 88-page ruling written by Associate Justice Paula Nakayama, the court ruled the commission failed to explain how its ruling affected traditional and customary Native Hawaiian practices.

The commission also did not completely analyze the effect on the public’s use of the streams, such as fishing or recreational activities, the high court said.

In addition, the commission did not adequately consider alternative water sources, such as recycled water and nonpotable wells, the court ruled.

The court concluded that the commission’s ruling must be struck down because the commission "did not discharge its duty with regard to the feasibility of protecting Native Hawaiian rights."

The ruling involves Na Wai Eha, "the four great waters of Maui," the name for the Waihee River and the Waiehu, Iao and Waikapu streams.

Because of the diversion, the Iao and Waikapu streams are dry, Moriwake said.

Moriwake said the groups were highly critical of the commission’s decision because the 12.5 million gallons was less than Hawaii Commercial’s last-ditch proposal of 16.5 million gallons.

Joshua Wisch, spokesman for the Attorney General’s Office, which represented the commission, said state attorneys are reviewing the ruling.

He said he couldn’t say whether more water will flow through the river and streams, because the commission, and not the state lawyers, will decide the issue.