The Marsh River watershed in northwest Minnesota is home to more than 36 fish species and 119 different aquatic insects. The abundance and diversity of aquatic life in the Marsh is due in part to the river’s close connection to the Red River of the North. Together these streams function as an interconnected system to provide crucial habitat for many species.
The Marsh River watershed gets its name from the vast prairies and numerous shallow wetlands that once dominated its landscape. Early settlers took advantage of the soils left by ancient Lake Agassiz to grow crops and raise livestock. People made extensive alterations to the landscape and streams to enhance farming even further. About 67% of the streams within the watershed have been altered, including all tributaries on the Minnesota side. The Marsh River is the only remaining natural watercourse in the entire watershed.
As part of monitoring and assessment work done in the watershed, the MPCA studied six sections of the Marsh River. Four sections fully supported fish and aquatic insect life, while two did not. The main contributors to aquatic life impairments include:
- Degraded habitat
- Extended periods of insufficient flow
- Excessive sediment clouding the water
The Marsh River is also impaired for swimming, meaning bacteria levels are too high at times to meet the standard designed to ensure safe contact with the water.
The diversity of life in the Marsh River system is worth protecting and restoring. However, there are some major impediments to restoring conditions that fully support aquatic life.
Drainage ditch networks impede the natural fish runways from the Red River and threaten the ability of these fish to reach the Marsh River and its tributaries. Another barrier to fish passage is the high gradient culvert at the confluence of County Ditch 11 and the Marsh River. Drainage of the tributaries within the Marsh River watershed is so effective that most of the tributaries go dry during the summer months.
Heavy silt deposits and poorly formed streams were also noted at each monitoring station. Protecting and restoring habitat for greater diversity of aquatic life will depend on:
- Establishing ways to control drainage while allowing streams to retain water
- Removing barriers to fish passage
- Creating buffers around all streams, rivers, and ditches using native perennial vegetation and trees
The loss of consistent flows in the watershed has been detrimental to habitat for fish and aquatic insects, but data suggest restoring flows has the potential for correcting this problem.
Excessive sedimentation exists in areas used by gravel-spawning fish and aquatic insects. Sediment clouds the water and makes it difficult for fish and other aquatic life to breathe, find food, and reproduce.
Although impairments have been identified throughout the watershed, the Marsh and its tributaries do in some places support extensive fish and aquatic insect populations. These places need protective strategies to maintain their conditions.
For more details of the river’s ability to support aquatic life and recreation, check out: