Bay Facts

Collectively, the Chesapeake’s three largest rivers—the Susquehanna, Potomac and James Rivers—provide more than 80% of the fresh water to the Bay.

Water temperatures in the Bay fluctuate widely throughout the year, reaching as high as 84 degrees in summer.

Salinity is highest at the mouth of the Chesapeake Bay, where water from the Atlantic Ocean enters.

Water temperatures in the Bay fluctuate widely throughout the year, dropping as low as 34 degrees in winter.

The Susquehanna River is the Bay’s largest tributary, and contributes about half of the Bay’s freshwater (about 19 million gallons per minute).

The Bay receives about half its water volume from the Atlantic Ocean in the form of saltwater. The other half (freshwater) drains into the Bay from the enormous 64,000-square-mile watershed.

The Chesapeake Bay holds more than 18 trillion gallons of water.

Most of the water in the Bay, including in the middle portion of the Bay and its tidal rivers, is brackish–a mixture of salty and fresh, with a salinity level of greater than 0.5 ppt but less than 25 ppt.

The Chesapeake Bay watershed has 150 major rivers and streams, but contains more than 100,000 smaller tributaries.