Total streamflow across the Casselman River was last observed at 836 cfs, and is expected to yield approximately 1,658 acre-ft of water today; about 84% of normal. Average streamflow for this time of year is 999 cfs, with recent peaks last observed on 2018-09-10 when daily discharge volume was observed at 20,470 cfs.

Maximum discharge along the river is currently at the Casselman River At Markleton reporting a streamflow rate of 707 cfs. This is also the highest stage along the Casselman River, with a gauge stage of 2.38 ft at this location. This river is monitored from 2 different streamgauging stations along the Casselman River, the highest being situated at an altitude of 2,135 ft, the Casselman River At Grantsville.

The Casselman River is a 56-mile long tributary of the Youghiogheny River located in western Maryland. The river was historically used for transportation and logging in the 1800s. Today, it is popular for fishing, kayaking, and other recreational activities. The river is fed by several tributaries and is home to several species of fish, including trout and smallmouth bass. The Deep Creek Dam on the river creates the Deep Creek Lake reservoir, which provides drinking water to the region and is a popular recreational area for boating and fishing. The Youghiogheny Reservoir, created by the Savage River Dam, also feeds into the Casselman River. The river is also used for agricultural purposes, with farms located along its banks. The Casselman River is an important natural resource for the region and its communities.