In a move all sides are calling historic, the Hawaii State Water Commission on Tuesday approved a mediated settlement that restores tens of millions of gallons of water a day to the Waimea River on Kauai.

The commission’s action in Honolulu concludes a yearlong mediation involving a Kauai community group, the state Agribusiness Development Corp., the Kekaha Agriculture Association, the Department of Hawaiian Home Lands and the Kauai Island Utility Cooperative.

In late July 2013 the Kauai community group Po‘ai Wai Ola filed a legal petition through Earthjustice asking the state Commission on Water Resource Management to allow more water to flow in the Waimea River.

Members of the group were upset the river was running dry even though the Kekaha Sugar Plantation, which began diverting water in the early 1900s, went out of business in 2001.

Turns out the state took over the plantation’s ditch network, with the state Agribusiness Development Corp. leasing the ditches and lands to the Kekaha Agriculture Association, a farmers cooperative that includes the area’s seed companies.

Earthjustice attorney David Henkin said that after the commission ordered mediation last year, the proceeding revealed the association was diverting more water than needed for agriculture and was instead using it to run an old hydropower plant.

In the process, he said, a lot of water was being dumped and wasted.

Under the settlement approved Tuesday, enough water will be returned to the river to sustain native stream life, support traditional Native Hawaiian practices and allow for future environmental and cultural projects. The accord includes provisions for real-time monitoring of water flows — information that will be available to the public.

Also under the agreement, the Kauai Island Utility Cooperative will be allowed to develop a new hydropower project that will use solar power to pump water uphill during the day and release it to generate power at night, and will provide water and other infrastructure to help the Department of Hawaiian Home Lands to establish new homes.

Henkin called the settlement historic because of the unprecedented agreement in contrast to previous water diversion controversies, including the Waiahole and Maui disputes, that lasted years and saw intervention by the state Supreme Court.

“This is an historic agreement,” agreed commission Chairwoman Suzanne Case in a news release. “During this process, the commission sought not only to resolve the claims brought by the Po‘ai Wai Ola hui, but to provide a mechanism for dealing with complex water issues holistically.

“Historically, Hawaii’s highly contentious water disputes have taken many years, if not decades to settle. Due to the incredible work by all parties involved, led by mediator Robbie Alm, this settlement was reached and finalized a little more than a year after mediation began,” she said.

Also quoted in the news release was Po‘ai Wai Ola President Galen Kaohi:

“Today’s agreement ensures that, for the first time in over 100 years, life-giving waters will once again flow continuously in Waimea River from mauka to makai, which is vital for the health of the river and our community.”