SALEM, Ore. — For most city dwellers, a water meter keeps track of every gallon that comes out of a garden hose or shower head.

But not so for their country cousins — mainly agricultural irrigators but also rural homeowners with wells — many of whom are holders of water rights.

But with pressure on limited water resources rising in the high desert and elsewhere, the Legislature is considering what proponents call a "baby step" toward a measurement system that might stretch the state's over-appropriated water supply.

The state Senate last week passed a bill that would enact a voluntary statewide tracking system overseen by the state's Water Resources Department. It is pending in the House.

"This bill is about moral persuasion," said Sen. Frank Shields, D-Portland. "If people change what they are doing and use less water, we all win."

Tight water supplies have long pitted irrigators against fishermen and environmentalists over who gets what.

Cities, too, want more water rights.

While a voluntary metering system may sound innocuous, Senate Bill 731 leaves irrigators wondering about motivation.

Sen. Doug Whitsett, R-Klamath Falls, who remembers the Klamath Basin water conflict in 2001, said the legislation would need only minor tweaking to require statewide metering.

Most farmers, he said, do not use all of the water to which they are entitled.

Sen. Jason Atkinson, R-Jacksonville, said some irrigation water helps wildlife by creating wetlands, and that could be lost if irrigation is reduced.

Farmers use only what they need, said Rex Barber, a Terrebonne farmer. "The insinuation that agriculture is wasting water just doesn't fly," he said.

Many worry that a voluntary system could become mandatory and require farmers to buy and install expensive meters. Some fear that irrigators then could be charged for the water they use.

A century ago, water rights helped develop land and agriculture, Barber said. Now, he said, the push for conservation threatens to limit that supply, increasing the cost of farming.

The state can require measurement on a case-by-case basis. Since 1995, the water agency has required meters at more than 9,000 points of diversion for new water-right permits.

Also, government agencies, cities, counties, schools and irrigation districts must report water use.

Conservationists complain that Oregon's water is allocated to the point where rivers could be fully drained.

"Installing head gates and meters on water diversions can be a tremendous boon to rivers," according to the Web site of Portland-based WaterWatch. "It can also help farmers spot problems with their irrigation systems and reduce their water use, leaving more in stream to support fish, wildlife and recreation."

Oregon water laws are based on "prior appropriation," meaning the first person to obtain a water right is the last to be shut off.

WaterWatch lobbyist Doug Myers said his group hopes grant money would help pay for meters but says the fear that farmers will be billed for water is "paranoia."

"I don't see the Legislature ever having the courage to charge for the use of the water, even though the water belongs to the people of the state," Myers said.

But Shields said the limited supply and rising demand for water will make it in this century what oil was in the last one.

"We need to be carefully watching and measuring all our uses of water; it's that important," he said.