Officials said that during construction, water levels in the reservoir will be lowered to accommodate the work, and recreational areas including Brighton Dam, Greenbridge, Triadelphia, Pig Tail and Big Branch are all being closed to the public.

The closures include picnic areas, boating and fishing — including shoreline fishing.

Brighton Dam Azalea Garden will remain open with limited parking, and the temporary visitors center is also open.

Officials said hunting will be permitted during scheduled seasons, but horse riding will be limited only to the “winter trail,” from December to mid-March.

Thousands of people use the Triadelphia watershed for recreation. In 2016, the WSSC issued almost 10,000 permits for various activities — though officials said that figure doesn’t reflect the total number of visitors.

Frederick Tutman, who serves as Patuxent Riverkeeper — part of the nonprofit program that works to preserve, protect and promote waterways throughout the region — said the WSSC project “is going to be a hit” to scores of outdoor enthusiasts.

“But you gotta do what you gotta do,” he said. “If I can’t make the dam go away ... I’m thrilled that they’re maintaining the infrastructure.”

Triadelphia is listed on the Patuxent Riverkeeper “water trail” sites and promoted as a prime spot for boats, canoes and kayaks.

“It’s a beautiful spot for a variety of uses,” said Tutman. “Two years is a long time. It’s going to be a huge inconvenience for some people.”

Luis Maya, a WSSC spokesman, said about 45 to 50 people attended a community meeting last month to learn about the project and ask questions.

“People are disappointed” about the loss of recreational access during the project, Maya said, “but there are other areas that are open for recreation use downstream.”

Specifically, the T. Howard Duckett Reservoir — along the border of Howard and Montgomery counties in the Burtonsville and Laurel area — will remain open.

Traffic on Brighton Dam Road will also be affected for the duration of the two-year project. Access will be reduced to one single lane over the dam, controlled by temporary traffic signals at each end.

Officials said motorists should expect delays, particularly during peak hours.

WSSC officials said they don’t expect environmental damage from the project.

In fact, Maya said the project will allow for dredging of the reservoir, so there will be the opportunity to clear silt.

A commission website devoted to the project — wsscwater.com/brighton — states that crews will clear debris and dispose of paint and other materials “in accordance with current industrial standards.”

The site also says officials “anticipate the fish population will survive the construction process as they have during other drought periods when water levels have been lower than normal.”

Brighton Dam was built in 1943 along the Patuxent to form the Triadelphia Reservoir. The reservoir holds about 6.3 billion gallons of water, and together with T. Howard Duckett, the two hold 12 billion gallons. Water from the reservoirs is filtered and treated by WSSC’s Patuxent plant and serves about 30 percent of WSSC’s customers. jjoyner@baltsun.com