House lawmakers are considering a measure that would conserve the island's finite supply of water by banning new golf courses that only use drinkable water to green their greens.

"As a golfer, I really like golf courses. But we have to make a policy decision. And, sorry folks, we need the water," said Rep. Ezra Kanoho, D-15th (Lihu'e, Koloa), chairman of the Water, Land and Ocean Resources Committee.

The measure — signed by 29 members of the House, advanced out of committee yesterday. It would require any golf course approved after Jan. 1 of next year, to install a water system that includes both drinkable and non-drinkable water.

That means that a developer could not build his golf course if he planned to lavish the course's rolling hills of grass with the same type of water that people drink.

To make limited supplies of water go further, a number of golf courses and large public spaces across the country — including Ko'ele Golf Course on Lana'i — use surface water and treated wastewater, or sewage, to quench the thirst of their plants and fill their landscaped ponds.

The state Commission on Water Resource Management said existing rules already support the intent of the bill. The commission is responsible for allocating the water held in the state's aquifers, which is the source of drinking water.

However, Rep. Cynthia Thielen, R-50th (Kailua, Mokapu), said lawmakers want to mandate the use of only undrinkable water on the courses.

Dean Nakano, acting deputy director of the commission, said the Legislature may run into jurisdictional problems with the proposed law because the commission has power only over designated water management areas — which include most of O'ahu, all of Moloka'i and a section of Maui.

Maui already has put in place a similar local law for its new courses, Nakano said.

Of O'ahu's 36 golf courses, 27 now use potable water, he said.