PORTLAND — The Portland Water District is taking a novel approach to pollution control by offering prizes to residents around Sebago Lake who help reduce phosphorus runoff.

District officials say the contest is a way of encouraging people to help maintain Sebago’s water quality. The lake provides drinking water to 160,000 people in Cumberland County and is a popular recreational area.

The district is giving out nearly $1,300 in prizes, including a hot-air balloon flight, water skis, golf passes and an assortment of gift certificates.

The contest is open to residents of the Sebago Lake watershed, which stretches from Bethel to Standish. The district wants them to create a buffer strip of vegetation between their homes and the water if they live near the lake and correct any erosion problems they spot.

The buffer strips will filter phosphorus-laden water that now has a clear path to the lake, officials say.

Although phosphorus is a nutrient that plants need for normal growth, too much of it flowing into a lake can cause an algae bloom that clouds and pollutes the water.

Unlike some other lakes, Sebago is not immediately threatened by algae, but district officials say overuse and development around the lake present a constant threat.

To win a prize, residents must take photographs before and after their work. The photos must be submitted by Aug. 15; winners will be announced Aug. 26.