The Mona Lake Watershed is located in the west-central portion of the Lower Peninsula of Michigan. It is almost entirely within Muskegon County with the exception of a small section of the northeast corner which is located in Newaygo County.

The watershed is approximately 45,570 acres in area and consists of four major water features: Mona Lake, Black Creek, Little Black Creek, and Ellis Drain. There are also several smaller tributaries that drain to Mona Lake including Cress Creek, five unnamed tributaries, and 140-plus storm drains that drain into either Mona Lake or its tributaries.

Generally the surface and ground water flow is from the northeast to the southwest. Mona Lake is located at the southwest end of the watershed and its discharge drains into Lake Michigan.

Within the Mona Lake Watershed are two counties (Muskegon and Newaygo), four cities (Muskegon, Muskegon Heights, Norton Shores and Roosevelt Park), and nine townships (Ashland Twp., Bridgeton Twp, Casnovia Twp., Egelston Twp., Fruitport Twp., Moorland Twp., Muskegon Twp., Ravenna Twp. and Sullivan Twp.).

Land use in the Mona Lake Watershed is widely varied. Agriculture remains the primary form of land use but a significant portion of the watershed has been developed for industrial, commercial, and residential use. Undeveloped wetlands and forests are also found in the watershed.