The sailing club was one of the first casualties at Lake Accotink, driven out by the mud bars that stretched their thick, black fingers across the waters. Then many of the canoeists decided to go, stopped by the ever-growing mud bars.

When lily pads started gobbling up even more open water, rowboat and paddleboat enthusiasts started leaving the lake.

Most of the fishermen gave up years ago. The fish population has long since diminished, depleted by pollution and runoff from nearby shopping center parking lots and suburban backyards.

And last summer the mallards started dying, victims of food poisoning picked up while scouring the lake bottom for bugs and picnic leftovers.

Lake Accotink is dying. If rescue operations don't start soon, Fairfax County park officials say it will be no more than seven years before the lake is consumed by silt and lily pads and pollution.

"The lake is being swallowed up," said Garth Redfield, a consultant hired by the county to study problems at the lake.

The recently completed year-long study, financed by a $141,000 federal grant, showed that Lake Accotink needs immediate and drastic surgery. Officials estimate the minimum cost of saving the lake--one of the largest recreational facilities in Fairfax County--at more than $1.5 million. jump

The Virginia Water Control Board has targeted Accotink as the Virginia lake most in need of restoration. Lake Fairfax, with many of the same problems as its older sister, also is high on the list of Virginia lakes needing restoration.

But the first problem of Fairfax officials will be money. The program that financed the lake study has been abolished by the Reagan administration.

With that source of funding dried up, the Fairfax County Park Authority has proposed setting aside $1.5 million for Lake Accotink, part of a $50 million recreation bond issue the authority hopes will be placed before voters in November. The county Board of Supervisors is expected to make a final decision on the bond proposal within the next few weeks.

Lake Accotink is the centerpiece of a 479-acre park just off the Beltway in Springfield. Since the lake opened about 40 years ago, it has shrunk about 40 percent, according to Gilman C. Aldridge, superintendent of the conservation division of the county Park Authority. About 24 acres of the 60-acre lake now are marsh or mud flats, unusable for most water recreation.

In the past three years, boat rentals and marine launches at the lake have dropped about 27 percent, Park Authority records show, although the park surrounding the lake attracted 293,400 visitors last year.

"The people who do go out are breaking paddles all over the place trying to push themselves off mud bars," said Aldridge.

Park authorities blame the problems on what they say has been the rapid, virtually unchecked residential and commercial development near the lake. Poor construction and landscaping practices, they say, have swept tons of dirt into the lake over the past several years.

"All lakes are doomed to die," said Aldridge. "All of them will eventually fill up with silt. But because of the human element here, the rate of deterioration has increased."

Conservationists estimate that the lake, one of two county-owned lakes in Fairfax, has collected more silt in the past 10 to 15 years that it collected in the previous 30 years. The lake originally was built as a reservoir for Fort Belvoir before it was turned over to the county for recreational use. The county began leasing the lake from the federal government in 1960 before taking it over completely in 1963.

The other county-owned lake, Lake Fairfax, just east of Reston, was built in 1956 and has escaped many of the problems at Lake Accotink because of county ordinances in the past decade setting stricter conservation requirements on development, park authorities said. Most of the work recommended for Lake Fairfax is aimed at preventing deterioration of the lake, officials said.

The water quality at both lakes is suffering from an overload of chemical and fertilizer pollutants, according to the recent study. The bigger problem is in Lake Accotink, however.

"The lake is overly fertilized and is unstable," Redfield said. For example, the water contains about 10 times the amount of phosphorous as should be allowable to maintain a lake with a high enough water quality to support a good balance of plant and animal life.

Much of the pollution comes from the tons of fertilizer suburban residents dump on their lawns each year.

"Every homeowner in Fairfax County wants a greener lawn than his neighbor," said Aldridge. As a result, he said, the wrong fertilizers in the wrong quantities are spread over lawns and left to drain into county streams and lakes.

Fertilizer and pesticides, two of the worst lake pollutants, combine with the runoff from roofs, streets and parking lots to drain through the ditches and streams of Springfield into Lake Accotink. The runoff--termed "non-point" pollution-- has left the waters of the lake murky and has sapped life-giving oxygen.

It also has fostered the growth of algae which has left the lake covered with a greenish-brown scum.

Lake Accotink was shut down for more than a year and drained in the early 1970s when officials discovered waste from a sewage treatment plant pouring into the lake's tributaries.

County officials say the current problems won't be solved so easily.

The consultant's study has proposed lengthy dredging, estimated to cost $750,000, for the lake. In addition, the consultants suggested building a wall, estimated to cost $800,000, through the lake to divert the incoming water and runoff, pushing it through the lake, rather than allowing it to settle on the lake bottom. Although the Park Authority has several proposals for implementing the plan, it has not yet decided which proposal to use.

If the dredging and channel wall are completed, the life expectancy of the lake would be another 60 years, the study said.

"We're talking about whether this lake lives or dies," said Redfield at a hearing last week designed to solicit public comment on the consultant's findings. "We think the lake is worth saving. After the restoration, fishing should improve, boating should increase, the water should be clearer and there shouldn't be algae scum on the surface."