Farmers, nurserymen and landowners want a state agency to take over operation of the Wahiawa Irrigation System, which includes Lake Wilson, to assure consistent water supply for one of the island's most productive agricultural areas.

With the pressure from development creeping into Waialua and the North Shore and threatening to reduce agricultural land, many see Wahiawa as a key to preserving O'ahu's agriculture resources and preserving agriculture requires access to cheap water.

"Most people do not really understand the importance of agriculture in the state of Hawai'i," said Susan Matsushima, a North Shore nursery owner. "It's not if another 9/11 hits, it's when another 9/11 hits we're not going to have enough food in the state."

Many Wahiawa farmers are hoping the Agribusiness Development Corp., an agency within the state Department of Agriculture, will operate and maintain the irrigation system that includes approximately 30 miles of ditches, tunnels and siphons that serve land from Wahiawa, Waialua and Hale'iwa.

The irrigation system is mostly owned by Dole Foods Hawaii and the Galbraith Estate.

The Galbraith Estate is dissolving and selling off its holdings, including the Lake Wilson dam and parts of the lake.

The irrigation system needs $4.2 million in immediate repairs and will need $2.98 million in future fixes, according to a recent study commissioned by the state. Operation and maintenance is estimated to cost $765,000 a year.

Dole Foods is completing about $2.1 million in upgrades to the system and is willing to donate its part of the system to the state.

State Rep. Michael Magaoay, D-46th (Kahuku, North Shore, Schofield), said he supports the transfer of the irrigation system to the Agribusiness Development Corp. to preserve agriculture land and open space.

"We're the last frontier as far as O'ahu is concerned," Magaoay said. "If you're looking at the growth of the state to be self-sustainable we need to provide infrastructure now instead of waiting when everything becomes forced. Then we pay more."

There are about 100 agriculture businesses using the Lake Wilson water, said Matsushima, the North Shore nursery owner. She said the estimated $7 million cost of the repairs to the system is reasonable to ensure future food production.

The University of Hawai'i has estimated that if Hawai'i were ever cut off from the Mainland, it has enough food on hand to last four days, Matsushima said.

Now is the time to be increasing agriculture production, but that can't be done without a dedicated water supply such as Lake Wilson and its irrigation system, she said.

The September 2007 Assessment of the Wahiawa Irrigation System, by Element Environmental LLC, was commissioned by Agribusiness Development Corp. after Dole, landowners and farmers approached the agency about taking charge, said Teena Rasmussen, Agribusiness Development Corp. chairman and owner of Paradise Flower Farm on Maui.

The study concluded there is a potential to increase agriculture land production by 1,000 acres if the state takes over the irrigation system.

That makes the takeover appealing, Rasmussen said, adding that there is widespread support for the move.

"The need is apparently there," Rasmussen said. "There are a couple months out of the year that they are not guaranteed water. It's not like there's no water out there. The delivery of the water is not regular."

But there are drawbacks, including liabilities from the system failing and the cost of maintenance and operation, Rasmussen said. The Agribusiness Development Corp. must weigh those against benefits and will make a recommendation to the state Legislature next year, Rasmussen said.

"My initial take on the whole project is it would be a good thing for the agency to take this on," she said.

Negotiations will have to include designating some of the land that the system feeds for agriculture use in perpetuity, Rasmussen said.

Agribusiness Development Corp. also owns and manages Waiahole Ditch on O'ahu and 12,000 acres of Kekaha sugar land and its water system on Kaua'i.

All of its systems must be self-sustaining, Rasmussen said.

Reach Eloise Aguiar at eaguiar@honoluluadvertiser.com.