Despite the return of normal rainfall to the Baltimore area since March, the city warned its water system customers yesterday to step up voluntary conservation or face mandatory curbs on water use.

In renewing the call to conservation, public works officials noted that while the city has seen normal rainfall since March - and in April, above-normal rainfall - the system's three major reservoirs remain 35 percent below normal levels and the region remains in a long-term drought.

The reservoirs, which public works officials said should be at 97 percent of capacity in late spring, are holding steady at 62 percent, even as the city continues to supplement its water supplies with 140 million gallons drawn each day from the Susquehanna River.

The city made the decision to tap the river in January when reservoir levels dipped below the lows reached during the summertime drought of 1999.

"Our customers should be aware that we are still experiencing a serious shortfall at our reservoirs," Public Works Director George L. Winfield said yesterday. "Although rainfall has returned to normal over the last three months, it has not been enough to make up for a deficit dating back to last summer. The choice is clear: Either voluntary conservation now or mandatory conservation later."

With more than 1.8 million people in metropolitan Baltimore depending on the city's water system, public works officials are concerned about usage as summer approaches.

Water use is traditionally highest in June as customers began filling swimming pools, tending lawns and gardens and washing cars.

Hot weather also brings another water-guzzler: illegally opened fire hydrants.

As much as 1,000 gallons of water a minute surge from an open hydrant, fire officials estimate, and public works officials urged that anyone seeing an open hydrant report it by calling 311.

"We want to emphasize this now more than ever: They have to be called in immediately," DPW spokesman Kurt L. Kocher said of the hydrants.

Heeding previous conservation alerts, city water customers have lowered average daily water consumption to 232 million gallons a day from 250 million, about 7 percent, public works officials said.

Winfield has said that he is reluctant to impose mandatory restrictions until required by the state drought management plan because less water means lower water revenues.

In April, Baltimore received its first month of above-normal rainfall since August. Rainfall at Baltimore-Washington International Airport totaled a little more than 4 inches, according to the National Weather Service.

That was an inch more than the April norm, which helped put a dent in the 12-inch deficit that had accumulated since August.

The above-normal precipitation trend continued last month, with rainfall at BWI totaling 2.74 inches, 0.13 more than normal.

Kocher said he thinks the meteorological good news has given the region's customers a "false sense that [the drought] is all over."

"Part of the problem is that you see these periodic rainfalls coming through and you think the drought is over," he said. "We need multiple rainfalls to get out of this."

Yesterday, public works officials highlighted three main actions customers can take to conserve:

Do not water lawns. Limit watering to gardens and landscaped areas. Use mulch to conserve soil moisture.

Do not wash cars at home. Use commercial car wash facilities because they recycle water.

Use washing machines and dishwashers only for full loads.

"We may get lucky," Kocher said. "We may have some prolonged periods of rain. But you can't count on luck, you have to manage these resources in the proper fashion."

More conservation tips are available at www.baltimore city.gov/government/dpw/savewater.html.