Green Bay (Lake Michigan) Depth Profile: Max 205 Feet

Green Bay is a 118-mile (190 km) long, 20-mile (32 km) wide bay of Lake Michigan, bounded by Wisconsin's Door Peninsula and the Upper Peninsula of Michigan.

Bathymetry

• Maximum depth: 205 ft (62 m) – near the center, north of Chambers Island.
• Average depth: ~60 ft (18 m).
• Volume: ~1,200 km³.
• Sill depth (entrance): ~30 ft (9 m) at Porte des Morts Passage – limits Lake Michigan exchange.

Why It Matters

• Stratification: Shallow + restricted circulation → summer hypoxia (dead zone) in bottom waters.
• Fisheries: Warm, productive—walleye, yellow perch, whitefish, sturgeon (recovering).
• Shipping: Dredged channel (27 ft) to Green Bay (city) port—coal, limestone, salt.
• Ice: Freezes solid most winters; icebreaking extends season.

Comparison

Lake Michigan max depth: 923 ft (281 m). Green Bay is a shallow, semi-enclosed sub-basin—more like a giant estuary than a lake.