The Rocky Gorge and Triadelphia reservoirs, which reach into Montgomery, Howard and Prince George's counties and are used by an estimated 200,000 vistors a year, are expected to be closed by the Washington Suburban Sanitary Commission next week as an economy measure.

The final decision, however, will be made Wednesday when the WSSC will decide whether to raise water and sewer rates for its 1.2 million suburban Maryland customers.

The bicounty agency announced the planned closings last month, and more than $1 million in other cutbacks, after a public hearing "made it clear there is no support for sewer and water rate increases" from the public or the Montgomery or Prince George's county councils, according to a WSSC spokesman.

While the commission has endorsed the cutbacks proposed by WSSC General Manager Robert S. McGarry -- including the reservoir closings -- it could decide to keep the reservoirs open, even without voting to increase water and sewer rates, or it could vote rate hikes smaller than the 13 percent mid-year increase it had proposed last month.

The WSSC says the cost of operating the reservoirs as recreation areas is about $200,000 a year.

The WSSC reduced water rates by 10 percent in June anticipating a normal summer, but when heavy rains reduced lawn and garden watering -- and WSSC revenues -- the agency announced a $2 million cutback in operating expenses and proposed a 13 percent general rate increase to begin Dec. 1. The additional $1 million in cutbacks, including the closing of the reservoirs, was announced Nov. 15, a week after the public hearing.

As part of its latest series of cutbacks, the WSSC also will eliminate 104 job positions from its 2,000-member staff, including six jobs connected with the reservoirs, will end guided tours at its plants, eliminate its research division, reduce routine maintenance of its system -- including its 24,000 fire hydrants in Prince George's and Montgomery counties -- and cut back on general repairs and replacements, according to public affairs director Arthur Brigham.

The two 800-acre reserviors, the largest lakes in suburban Maryland, and the 6,000 acres of fields and woods that surround them are among the county's most popular fishing areas. In 1978, 3,051 season-long, $10 fishing and boating permits were issued, as were 6,995 one-day, $1 fishing and boating permits and 427 $10 mooring permits.

The area around the reservoirs also contains a number of horseback riding trails, for which 45 people bought $10-a-year use permits in 1978.

In all, the recreational fees brought in close to $42,000 that year.

"The reservoirs are like lakes in Canada, almost wilderness," said one fisherman, William Lowe of Ellicott City, who said he has been coming to Triadelphia since it was built in 1943 when he was a boy. Rocky Gorge -- officially named the T. Howard Duckett Reservoir -- was completed in 1954.

"Why stop the fishing? It's probably one of the few things that pays for itself . . . I'd even like to see them double the fee to $20 rather than close the reserviors," Lowe said last weekend as he and his 14-year-old son, Kevin, where taking their boat from its rented mooring on the banks of Triadelphia.

"Ive been fishing and hunting here ever since I was a little kid. It's a damn shame they're going to close this down. People have got to go somewhere," said Al Carnahan of Rockville, who was hunting for deer last weekend in one of the wooded sections open to hunting around Triadelphia Resrvoir.

Ben Popera of Brookville, and his son Greg, 16, live about five miles from Triadelphia, where last week they too were taking out their small fishing boat for what they feared was the last time.

"The advantage of these reservoirs is you don't have to spend a lot of time and gasoline driving somewhere to fish," said Popera, who has caught pike and large and small mouth bass in Triadelphia but admits it's often "hard fishing."

The six Montgomery chapters of the Izaak Walton League of America have opposed the reservoir closings, according to regional vice president Jerry Jump.

"Some people see it as a ploy to get pressure for a rate increase. I don't know about that, but I do do know it's a bad precedent even to threaten to close down what have been considered public areas for decades," said Jump. "It will cause the public to think twice if the WSSC ever wants to create a new impoundment somewhere."

Thomas W. Fisher, the league's Maryland executive secretary, said, "I don't understand the heavy cost of operation, but sportsmen already pay fees to use the reservoirs when many other reservors are open to the public free. In fact it's always galled me to have to pay WSSC for a fishing license in addition to the state fishing license."

The cost of maintaining the reservoirs is only a small part of the WSSC budget and a small part of the budget cuts. Only six of the 104 staff positions being eliminated and $136,000 of the more than $1 million in recent budget cuts affect the lakes.

The six staffers, three maintenance men and three guards, represent $106,000 in annual salaries and fringe benefits, according to WSSC spokesman Brigham. Presently the reservoirs are operated by a staff of 21. In addition, there are about $30,000 in recurring expenses, Brigham said, such as $5,000 for stocking fish, and $7,000 for supplies. In addition, expenses include an average of about $60,000 a year in nonrecurring expenses such as paving roads and parking lots, buying picnic benches and publications about the reservoirs.