Explore the Watershed

Chesapeake Bay watershedThe Chesapeake Bay is North America’s largest estuary, and the third-largest such formation in the world.  An estuary is defined as the wide, lower course of a river where its currents are met by the tides, and as an arm of the sea that extends inland to meet the mouth of a river.  The Bay meets these definitions perfectly.

The Chesapeake Bay itself:

  • Formed about 12,000 years ago as melting glaciers flooded the Susquehanna River Valley
  • Is about 200 miles long, running from Havre de Grace, Maryland, to Norfolk, Virginia
  • Varies in width from 3.4 miles near Aberdeen, Maryland, to 35 miles at the mouth of the Potomac River
  • Has an average depth of only about 21 feet (except for a few deep troughs thought to be remnants of the ancient Susquehanna River, which form a channel deep enough to allow the passage of large commercial vessels)
  • Holds on average more than 15 trillion gallons of water

More than 500 million pounds of seafood are harvested from the Bay every year.


Information and image provided by the Chesapeake Bay Foundation and Chesapeake Bay Program.