Fig. 4. Cumulative distributions of measured seven-day annual low flows for several stations in the Potomac River Basin. (A) Two headwater tributaries. Solid line: Savage River (U.S. Geological Survey station 1596500); broken line: Wills Creek (U.S. Geological Survey station 1601500). Points were estimated using the empirical model of Carpenter and Hayes (1996). Solid circle: Savage River; open circle: Wills Creek. (B) Potomac River near Washington, D.C. Solid line: unadjusted data (U.S. Geological Survey station 1646500); broken line: adjusted data (U.S. Geological Survey station 1646502).