There are more than 100 dams in the Kalamazoo River watershed registered under Michigan DEQ with 13 on the Kalamazoo River mainstem. Not all dams are required to be registered with the state and many smaller, unregistered dams are scattered throughout the tributaries and headwater streams of the watershed. Dams along the Kalamazoo River and its tributaries are mostly “run-of-river” dams that do not change much in stored water volume over the seasons. The first dams were built across small creeks at high gradient locations to power grain and saw mills. Construction of mill dams began in the 1830s and continued until 1900. From 1890 to 1940, several large dams were constructed to generate electricity.
The last phase of dam building was happened between 1945-1980. These dams were built to control lake levels from recreation and waterfront development. The dam that forms Morrow Lake near Comstock (Kilowatt Dam) is an exception and was originally constructed to create a reservoir to provide cooling water for a coal burning power plant. It was later retrofitted to produce a modest level of electric power.
Dams six feet or more in height and/or with impounded capacity at design flood elevation of five surface acres or more are regulated under State of Michigan law and in some cases under FERC, the Federal Energy Regulatory Commission. Most dams that do not fall under state or federal regulations are managed and maintained under the sole discretion of the private owner.
Dams have detrimental effects on aquatic communities in rivers. They impede fish movements, fragmenting fish populations and blocking spawning migrations. Dams were traditionally built at high quality river habitats with fast moving water. Dams interrupt the river systems, turning them into slow moving pond-like habitats. Some fishes and other aquatic animals need to be able to move upstream and downstream during different times of the season. Mortality or injury can result when fish and animals pass through dams, especially those with hydroelectric turbines.
Impoundments that discharge water from the surface typically increase downstream water temperatures by spilling warm surface waters. This is especially critical in the warm summer months. Increased water temperatures can lead to elimination of certain aquatic species including fish. Evaporation rates increase with the higher temperatures and greater surface area in the reservoir. Dissolved oxygen which fish and many aquatic animals depend on, are often much lower in the impounded portion of the river compared to fast flowing waters.
Reservoirs also act as sediment and debris traps, and often contain historical accumulations of contaminated sediments. Some of the most problematic and decrepit dams along the Kalamazoo River hold back high volumes of PCB-contaminated sediments, with the largest proportion of PCBs in Lake Allegan. Read more about the history of PCB contamination and progress on the cleanup.
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