Monocacy River River Levels

Last Updated: December 4, 2025

The Monocacy River is a 58-mile-long tributary of the Potomac River that flows through Maryland and Pennsylvania.


Summary

Total streamflow across the Monocacy River was last observed at 973 cfs, and is expected to yield approximately 1,929 acre-ft of water today; about 57% of normal. River levels are low and may signify a drought. Average streamflow for this time of year is 1,703 cfs, with recent peaks last observed on 2021-09-02 when daily discharge volume was observed at 62,500 cfs.

Maximum discharge along the river is currently at the Monocacy River At Jug Bridge Near Frederick reporting a streamflow rate of 479 cfs. However, the streamgauge with the highest stage along the river is the Monocacy River At Bridgeport with a gauge stage of 3.17 ft. This river is monitored from 3 different streamgauging stations along the Monocacy River, the highest being situated at an altitude of 332 ft, the Monocacy River At Bridgeport.

River Details

Last Updated 2025-12-04
Discharge Volume 1,929 ACRE-FT
Streamflow 972.5 cfs
+321.6 cfs (+49.41%)
Percent of Normal 57.11%
Maximum 62,500.0 cfs
2021-09-02
Seasonal Avg 1,703 cfs
       
River Streamflow Levels
Streamgauge Streamflow Gauge Stage 24hr Change (%) % Normal Minimum (cfs) Maximum (cfs) Air Temp Elevation
Monocacy River At Bridgeport
USGS 01639000
80 cfs 3.17 ft 165.89
Monocacy River At Monocacy Blvd At Frederick
USGS 01642190
414 cfs 2.45 ft 73.22
Monocacy River At Jug Bridge Near Frederick
USGS 01643000
479 cfs 2.53 ft 25.39
Seasonal Discharge Comparison
Maximum Streamflow Discharge
Streamflow Elevation Profile

The Monocacy River is a free-flowing left tributary to the Potomac River, which empties into the Atlantic Ocean via the Chesapeake Bay. The river is 58.5 miles (94.1 km) long, with a drainage area of about 744 square miles (1,930 km2). It is the largest Maryland tributary to the Potomac.
The name "Monocacy" comes from the Shawnee name for the river Monnockkesey, which translates to "river with many bends." (However, another local tradition asserts that "Monocacy" means "well-fenced garden" in an Indian language.) The first town ever settled in Western Maryland, Monocacy, also gets its name from this river.
The Monocacy National Battlefield lies alongside part of the river, marking an 1864 engagement during the American Civil War, the Battle of Monocacy Junction. The Chesapeake and Ohio Canal crosses over the river at the Monocacy Aqueduct, the largest of the 11 aqueducts on the canal.