One of the state's leading environmentalists called Friday for permanent outdoor watering restrictions during daylight hours, and metro Atlanta's environmental planner agreed.

Sally Bethea, executive director of the Upper Chattahoochee Riverkeeper, an environmental advocacy group, said the region should ban daylight lawn and garden sprinkling even after the current drought eases.

"They do it in Austin (Texas) and Jacksonville," Bethea said.

She added that year-round, clearly defined rules would be easier to follow than the changing chessboard of state regulations overlaid with different local requirements.

"I keep getting confused as to when I can or can't water," she said.

More than half the water used during the heat of the day is lost to evaporation. Gardening expert Walter Reeves says the ideal time to water the lawn is between 10 p.m. and 9 a.m.

Current state rules limit most outdoor watering to the hours from midnight to 10 a.m. In metro Atlanta, only hand-held garden hoses can be used for 25 minutes on a three-day-a-week schedule based on street address.

Bethea made her remarks in Midtown Atlanta at the monthly Sustainable Atlanta Roundtable meeting hosted by Southface, which promotes sustainable development. The topic was water conservation.

During the question and answer period, the Atlanta Regional Commission's environmental planning chief, Pat Stevens, said, "I like the idea of some permanent outdoor restrictions."

One permanent, year-round outdoor watering rule is already in place statewide: the three-day-a-week schedule. Bethea was a member of the Georgia Board of Natural Resources when it adopted the rule in 2003. Even when there is no drought, home and business owners are supposed to water only on Tuesdays, Thursdays and Sundays if they have an odd-numbered street address, and Mondays, Wednesdays and Saturdays if they have an even-numbered or unnumbered address. No one can water on Fridays.

Enforcement is left to individual water providers, usually city and county governments. Before the drought, few people were aware of the rule and enforcement was typically lax.

Bethea listed two other must-dos for metro Atlanta to avoid running out of drinking water as it continues to grow. Fix leaky underground pipes that carry treated drinking water to individual buildings, and replace old toilets with low-flow toilets that can save as much as 5 gallons a flush.

"To avoid the collision course we are most assuredly on ... we've got to take smart and really aggressive action now because we're nearly tapped out," Bethea said.