Raleigh probably will follow Durham's lead and raise water rates this year -- in part, ironically, because conservation is working -- city officials said Tuesday.

Because of the city's mandatory water restrictions and voluntary conservation, Raleigh is selling about 20 percent less water than this time a year ago -- and earning 20 percent less revenue.

The city's utilities are self-financing, so water revenues must pay for water system operations, expansions and improvements.

Since operating costs are fixed and construction projects are necessary, the only option is to raise rates to make up for the lost revenue, city Pubic Utilities Director Dale Crisp said in a meeting of state and local water managers.

Raleigh used about 41 million gallons a day during the past month, compared with 51 million gallons a day during the same period a year ago, he said.

Durham's City Council decided Monday to raise the city's water rates starting July 1.

In Raleigh, "there will have to be a reckoning at some point," Crisp said. "Our turn is coming."

Even though the Triangle is emerging from a yearlong drought that drew Raleigh's water source, Falls Lake, perilously low, Raleigh remains the only city in the Neuse River basin with mandatory water restrictions, Crisp said.

If Raleigh lifts its Stage 1 restrictions, water use will rise, he said, though lawn irrigation probably will be more tightly regulated than in years past.

"I don't think we're going to let usage go up as high as it did last year, because we've learned that irrigation is such a heavy demand on our system," Crisp said.

Raleigh Mayor Charles Meeker said another factor that may prompt rate increases is the need to pay for a new water treatment plant at Lake Benson near Garner, which is to open in 2010.

"There's no choice," Meeker said Tuesday. "You can't build something without paying for it."

Meeker said Raleigh's City Council will discuss its rates during June budget deliberations.

"Our water rates are still well below everybody else's in the area," he said.