The Board of Water Supply has been working with people living in the Ko'olau Loa district in Windward O'ahu to create a watershed management plan for the district — and one theme already surfacing is residents' desire to keep Windward water on the windward side.

For longtime Punalu'u rancher Mahi Trevenen, a plan is necessary to secure the future of agriculture in his valley. Trevenen, 79, continues to raise cattle in the valley as his grandfather did, using water from an old ditch left over from a sugar plantation. Trevenen said he feels the pressure of development encroaching on the water as people try to build country estates, threatening the rural Windward way of life.

"It's something I really cherish," Trevenen said. "That's what I grew up with."

Others in Ko'olau Loa said they feel the same and have participated in several meetings to discuss the plan with the water board and its consultant, Jeff Overton of Group 70 International.

The plan, costing about $350,000, is one of five the board is doing to fulfill a mandate by the state and city to produce a county water plan that will be used in conjunction with the city's sustainable development plan.

Barry Usagawa, head of the board's Water Resource Division, said the other regional plans are for Wai'anae; the North Shore; Ko'olau Poko; and a plan that will include 'Ewa, Central O'ahu, and urban and East Honolulu.

The plan will be developed with the intention that Windward water will stay on O'ahu's windward side, Usagawa said.

"We learned a lot from the Waiahole Ditch case," he said. "We really don't know how much water there is on the windward side."

Waiahole Ditch was developed in 1916 to irrigate sugar crops in Honolulu. When the sugar industry died, Windward activists and farmers fought to have the water remain on the windward side. The issue reached the Hawai'i Supreme Court, which ordered the water commission to reconsider how to allocate the Waiahole Ditch water based on how much water Windward streams need to stay healthy.

The plans will reflect the board's change in policy, Usagawa said.

"We're not just looking at use and developing (water sources)," he said. "We're looking at protection and restoration, forestry management. If the forest isn't healthy, then it's not going to capture the rainfall, slowing the runoff down and percolating through the ground so it sustains the aquifers. It's all connected."

The Ko'olau Loa plan will include projects to protect and sustain the health of the watersheds.

Proposals include groundwater source protection, near-shore water monitoring, a fishpond restoration and irrigation systems maintenance, Usagawa said.

Financing for all the projects still has to be worked out.

"The plan needs to be done," said Creighton Mattoon, president of the Punalu'u Community Association. "It probably needed to be done sooner. This is one of our great resources, but it's finite and when we run out of fresh water, what?"

Plan is to keep Windward water on windward side