Officials in Charles County and St. Mary's County have asked customers of public water systems to voluntarily conserve water, saying supplies are strained by the long-running drought.
St. Mary's officials banned most outdoor water uses in one neighborhood served by old, small pipes. About 100 families were affected.
In Waldorf, water use is running roughly 30 percent above normal, with lawn watering a leading cause, said Michelle Cutler, operations superintendent for the Charles County water system, which supplies about 52,000 people.
Charles officials issued their conservation appeal Friday. In St. Mary's County, the Metropolitan Commission on Wednesday urged its 28,000 customers to limit outdoor water use.
Calvert County officials have not issued a conservation appeal.
The three Southern Maryland counties, like much of the region, are suffering a drought that has left rainfall below average since last June.
The mandatory ban on watering lawns, washing cars and filling swimming pools affected southern parts of the Town Creek subdivision in Lexington Park. Violators face a fine of up to $100 and 30 days in jail.
The area is served by old water lines that cannot maintain pressure as heavy water use continues, said Metropolitan Commission Director Steven L. King.
Josie Newland's home is among those affected by the order. "We do have a big lawn, but we've decided we can't keep it watered as much as we'd like," Newland said.
In Charles County, Cutler said reduced use now could reduce the chances of drawing down the deep underground reservoirs, called aquifers, that supply the public water system.
"If this continues, it will put a toll on the aquifers. And we just don't want that to happen," Cutler said.
Officials urged residents to curtail unnecessary outdoor use, including watering lawns and washing cars.
They asked residents to fix leaky valves and faucets; to not leave water running while shaving, brushing teeth or washing fruits and vegetables; and to run the dishwasher or washing machine only when there is a full load.
Cutler said that residents have responded to past appeals to conserve.
"Most of the people will cut back when you ask them to," she said.
King, of the St. Mary's water authority, said dry weather has arrived earlier than usual.
"It's normal for this to happen in July and August. That's what's worrisome, that this is coming early," King said. "The challenge for our customers is to try to be conservative with the resource and not use a lot of water that could overtax the system."
In the past two weeks, water usage in all of the commission's service area went up dramatically, King said. At Lexington Park, the service area with the most residents, water usage rose from 19 million gallons during the week of Memorial Day to 30 million gallons last week, King said.
At Breton Bay, residents were consuming 1.6 million gallons on Memorial Day week. Last week, usage was up 2.7 million gallons, he said.