Horseback riders, fishermen, boaters and picnickers will have to pay higher fees — and in some cases new ones — to use the Washington Suburban Sanitary Commission’s two Patuxent River reservoirs and the surrounding woods starting March 15, according to new WSSC rules.

The regulations, issued late Tuesday, also will allow hiking and bird-watching for the first time at the Rocky Gorge and Triadelphia reservoirs.

Horseback riders will be allowed to return to decades-old equestrian trails that WSSC suddenly put off limits in May 2011, citing concerns about animal waste runoff into the reservoirs’ drinking water supply. A follow-up environmental consultant’s report found that the trails caused significantly less sediment runoff than the road WSSC began requiring riders to use.

Seasonal permits will increase to $70 from $60, and single-day permits will increase to $6 from $5. A new picnic fee will vary by the group’s size but will be $6 for up to five people. People 65 and over can still use the areas for free. The utility issued about 5,600 recreational permits last year.

Nearby stables whose clients use the trails must pay a new $250 annual permit fee, and adjacent landowners who use them will have to buy an $80 annual permit.

WSSC officials say the higher permit fees are needed to help pay for upkeep, including improved litter pickup. The utility backed off an earlier proposal that would have required horseback riders to remove horse droppings from trails. Instead, they will have to remove droppings only from parking lots and paved roads.

In a letter accompanying the new rules, WSSC General Manager Jerry N. Johnson said, “Our goal is to achieve a balance which allows for reasonable recreational use of the watershed while not surrendering our responsibility and commitment to WSSC customers in protecting water quality.”

The recreational areas also will be open 30 days longer, from March 15 to Nov. 30.

An advocate for the local equestrian community said horseback riding should be allowed during the dry winter months.

Riding used to be permitted year-round but is now limited to March 15 to Nov. 30, which WSSC officials say is necessary to limit erosion.

“We don’t ride when the ground is muddy and slippery,” said the advocate, Barbara Sollner-Webb.

Sollner-Webb said she and others will continue to urge WSSC to make changes, including lifting a prohibition against horseback riders clearing trails of branches that can poke them in the eye or spook horses.

WSSC spokesman I.J. Hudson said equestrian advocates have been told that the new rules, as a “common sense” matter, would not forbid trimming branches that would harm a rider. The prohibition against cutting and trimming, he said, is to discourage people from trying to create new, unauthorized trails through the woods.