Watershed Management Area 10 (WMA10) includes the Millstone River and its tributaries. The Millstone River is a tributary of the Raritan River. WMA10 includes parts of Hunterdon, Somerset, Middlesex, Mercer, and Monmouth counties. Land use in the area is mainly suburban development with scattered agricultural areas. Extensive, recent development, however, has continued to emerge in the upper portion of the watershed. Since the 1930s, overall agricultural lands in the watershed have diminished, while urban areas have increased. Despite this shift to urbanization, the watershed has experienced only a 2% loss of wetland and 5% of forested habitat (as of 2002). Many water quality issues have risen from the surge in urban and suburban development, including runoff from increased impervious cover, construction sites, suburban surfaces, storm sewers, and roads. Septic systems are felt to be a potential pollution problem throughout the watershed. In some areas, this poses a severe threat to the groundwater.

Despite increasing suburban development, there is still considerable wildlife habitat and a strong native biodiversity in the region. Over 89 species of birds are present in the watershed, including Owls, Yellow-Breasted Chat, Yellow-Billed Cuckoo, a variety of Woodpecker species, Warblers, and the Northern Mockingbird. The watershed also provides habitat for a variety of mammals, such as the Meadow Jumping Mouse, Eastern Cottontail, White-Tailed Deer, Coyote, Red Fox, Eastern Red Bad, and Black Bear. A wide variety of reptiles, amphibians, and butterflies also live within the region of WMA10.

The Stony-Brook Millstone Watershed Association is a key organization in this region, helping to mobilize the community through education, advocacy, and effective citizen action to promote environmental stewardship in the watershed.