Portage Lake is a 510-acre glacial lake located near Mendon in St. Joseph County, Michigan. The lake features a maximum depth reported between 37-60 feet and is fed and drained by the Portage River, which flows through the lake from north to south.

The lake offers excellent paddling opportunities with a public boat launch located on the southwest side that can accommodate 30 vehicles with trailers. Access is easy from this State of Michigan-owned facility. The lake serves as the starting point for one of the county's most popular paddling routes - from Portage Lake down the Portage River to Parkville Road in Park Township, which takes approximately two hours to complete.

Portage Lake maintains high water quality standards, having the best water quality of any waterways in the area. The lake bottom consists primarily of sand, gravel, and organic material. Water clarity is good, with summer Secchi disk readings of 6 feet. The lake stratifies during summer months, with dissolved oxygen depletion occurring in deeper waters.

Wildlife viewing opportunities are abundant. The lake supports diverse fish populations including bluegill, yellow perch, black crappie, largemouth bass, and northern pike. Turtle species are commonly observed, including map turtles and painted turtles. The surrounding area provides habitat for various bird species, making it popular with birdwatchers.

Approximately 46% of the shoreline features cottages and homes, while the remainder consists of wetlands and wooded areas, providing a mix of developed and natural scenery. The lake connects to extensive wetland areas in the northern section, offering additional exploration opportunities for paddlers.

The lake experiences recreational traffic but is not typically overcrowded. Bass fishing tournaments are held periodically. The combination of good water quality, wildlife viewing, and connection to the popular Portage River paddling route makes this an attractive destination for paddlers of various skill levels.