NARRAGANSETT — Southern Rhode Island has enough water to allow for some growth, but only if residents stop wasting it, a partnership of environmental and economic groups says.

Members of the Coalition for Water Security see danger ahead and think the state needs policies for managing water supplies.

“We shouldn’t say no to economic growth” because of a shortage of water, said Cynthia Giles of the Conservation Law Foundation, one of the coalition’s member groups, “when we’re spreading that water on our lawns.”

On a hot summer day when a system such as North Kingstown’s is pumping as much water as possible and residents still want more, Giles said Wednesday at a forum on the future of Washington County’s water, “What if there’s a fire?”

A tapped-out water system can’t produce the water pressure to fight a fire. That could lead to disaster.

“If people are using more than wells can produce,” said Susan Licardi, director of North Kingstown’s Water Department, “there’s nothing you can do about it.” Enforcing odd-even lawn-watering days is difficult, she said. “In July and August, peak daily usage bumps against capacity.”

Household water use can go from an average of 20,000 to 30,000 gallons per quarter to 200,000 to 300,000 gallons per quarter in the summer, when people water lawns and gardens.

The town has worked with the University of Rhode Island’s Healthy Landscapes program “to show people they can have nice landscapes without using so much water,” and newsletters with conservation tips go out with quarterly bills. Next could come limits on landscaped areas.

“We’re drinking-water suppliers,” Licardi said., but “most of the water is going to lawns rather than drinking.”

Steven King, managing director of Quonset Development Corporation, said the 168 businesses on the industrial park’s 1,000 developed acres must do outdoor watering only at night and refrain during drought conditions. They get a 25-percent rebate for installing low-flow toilets and faucets. His office uses low-flow fixtures, storing enough rainwater in cisterns to keep the grass alive for a month, and landscaping with drought-resistant plants.

At URI, which runs what facilities executive J. Vernon Wyman called “probably the largest housing and restaurant operations in Rhode Island,” conservation measures produced a 12-percent reduction in water use between 1999 and 2003, even though “our enrollment had increased and we had brought some new buildings on line.”

Parking lots at Boss Arena and the Ryan Center, he said, have porous pavement that allows rainfall to recharge the aquifer from which URI pumps its water. More efficient dishwashing equipment was installed in the new dining hall, and repairs to the campus steam-heat system are stopping leaks. And energy savings could be used to help pay for the equipment that will recycle water in an aquaculture project at East Farm, in South Kingstown.

“While we have all this creative activity going on the institutional side,” said Scott Wolf, executive director of Grow Smart RI, another of the coalition’s partners, “we still have this big problem of residential overuse of water.

“I’ve learned that if you just have an inch a week of water, your lawn will be OK,” he said.

Giles agreed. “We’re way overdoing” the lawn watering, she said. Most simply evaporates, and overwatering can weaken the grass.

It’s not true that more is better, Giles said. “More is worse.”

dnaylor@projo.com