USGS - science for a changing world

Water Science for Maryland, Delaware and the District of Columbia


Streamflow data are most commonly used for assessing water supply and to determine the risk of droughts and floods. Streamflow data are also used to calculate loads of chemical constituents, and to assess how biological communities are affected by hydrologic conditions.

The USGS streamgages chosen for the monthly water summary were selected based on the following criteria:

  • Minimum period of record is 10 years of continuous data
  • Watershed areas greater than 5 square miles
  • Streamflow is not regulated, such as by a dam or diversion, and it has relatively natural flow
  • Streamflow data reflect to weather condition
  • Most of the surrounding area and watershed are not urban

Of the 33 streamgages used in this summary, 22 have more than 60 years of data, allowing for comparison to data from the historical droughts of 2002 and the 1960s. All 33 streamgages have at least 30 years of monthly mean streamflow data.

November 2018 Streamflow

Monthly mean streamflows were at record November highs at 20 streamgages and above the 90th percentile at 13 streamgages. Monthly mean streamflow increased at 33 streamgages (100 percent) between October and November.

Click here to access the clickable streamflow map

In the hydrograph for the selected streamgages, the dark line in the 5-year hydrograph represents the monthly mean streamflow for this period, and the white band shows the normal range (25th-75th percentiles) based on the period of record. The maximum monthly mean streamflow is at the top of the blue shaded section, and the lowest monthly mean streamflow is at the bottom of the tan area. Each monthly mean streamflow is colored according to the percentile rank compared to the historical data for the month.

Monthly mean streamflow at Deer Creek at Rocks, Harford County, Maryland, was 397 cubic feet per second (ft3/s), which is a record November high. The previous record was 266 ft3/s, set in 1926. Record-keeping at this streamgage began in October 1926

At the Monocacy River at Jug Bridge near Frederick, in Frederick County, Maryland, the monthly mean streamflow was 4,430 ft3/s, which is a November record high. The previous record of 2,500 ft3/s was set in 1932. Record-keeping at this streamgage began in October 1929.



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