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River of Change
The Potomac River at Great Falls
The Potomac River begins as a small spring near Fairfax Stone, West Virginia. Like a giant funnel it gathers water from Pennsylvania, West Virginia, Maryland, Virginia, and the District of Columbia as it travels 383 miles to the Chesapeake Bay.
When it reaches Great Falls, the river narrows and drops 76 feet into a canyon called Mather Gorge. Changing weather conditions in the river's watershed affect the character of the river at Great Falls.
During dry periods the river shrinks to a trickle on the face of a rock wall.
At average flow, the river cascades over the rock into a 25-foot deep pool.
Within 72 hours after a snow melt or heavy rains upstream, the Potomac swells. Sometimes the flow is so great that all the water cannot force its way through the narrow entrance of Mather Gorge. When this happens, the river backs up, covers the falls and floods the riverbank. |