USGS Water-Year Summary 2021
01661500 ST MARYS RIVER AT GREAT MILLS, MD
LOCATION - Lat 38°14'30.3", long 76°30'13.2" referenced to North American Datum of 1983, St. Mary's County, MD, Hydrologic Unit 02070011, on left bank at downstream side of bridge on State Highway 471 (Indian Bridge Road) in Great Mills (formerly Clifton Mills), 0.3 mi downstream from Western Branch, and 12.0 mi upstream from mouth.
DRAINAGE AREA - 24 mi².
- WSP 1702: 1946, 1948-49, 1955, 1957-58. WDR MD-DE-83-1: 1981-82(M).
PERIOD OF RECORD - June 1946 to September 2005. October 2006 to current year.
GAGE - Water-stage recorder, crest-stage gage, and concrete control. Datum of gage is 6.86 ft above North American Vertical Datum of 1988.