Sebago Lake - Water Supply

Water Supply

Sebago Lake is the primary water supply for the Portland Water District, which serves the Greater Portland region and about 15% of Maine's population. The lake's watershed is more than 50 miles (80 km) long and covers parts of 24 Maine towns.

The lake holds roughly 995 billion US gallons (3.77×109 m3) of water that on average resides 5.1 to 5.4 years in the lake. The direct watershed is about 171 square miles (443 km2) of land plus the 45 square miles (117 km2) of the lake, and the indirect watershed about 190 square miles (490 km2) of land plus about 28 square miles (73 km2) of other bodies of water. As of May 1990, roughly 86% of the watershed was forests and fallow fields, 2.5% in active timber operations, 9.3% in residential, agricultural, and commercial use, and 2.2% used for other purposes. Water inflow is estimated at 544 million US gallons (2,060,000 m3) per day and outflow at 498 million US gallons (1,890,000 m3) per day, of which 24 million US gallons (91,000 m3)/day are for the water district.