The diagram shows this better than I can explain it. At a gage height of 1 foot, our stream has the amount of water (flow) represented by the blue area. Let's say it rains and the water rises to 2 feet. The additional flow is represented by the green area.
Closest Airport to Washington, D. C., DC. The closest airport to Washington, D. C. is Ronald Reagan Washington National Airport (DCA). Distance from Ronald Reagan Washington National Airport to Washington, D. C., DC is 4,8 kilometers (3,0 miles).
The Dulles Airport is 26 miles from Washington DC and has 139 airline gates. In 2012, it handled more than 22.5M passengers including both domestic and international travellers.