Ottawa River Coalition | Lowhead Dams
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Lowhead Dams

Lowhead Dams

Because we are a headwaters stream system, flow or the amount of water in the stream channel has historically been challenged, especially in the summertime when precipitation is less frequent.  Therefore the installation of low head dams that span the entire width of the stream bed date back to the early 1900s in the Ottawa River watershed.


Eight lowhead dams are located within the Ottawa River main channel.  The Allentown lowhead dam was installed in 1933 in support of a stream flow gauging station that was operated by the U.S. Geological Survey agency until 1984.  The five lowhead dams in the City of Lima were constructed between 1931 and 1956 to create impoundments of water where otherwise a dry stream bed existed.  The Metzger Road low head dam creates an impoundment for the continual withdrawal of water by the City of Lima into the Ferguson and Metzger Reservoirs.  Just upstream of that dam and downstream of Fetter Road in Bath Township is a lowhead dam that was once utilized to impound water for withdrawal into Lima Lake, a water body now only used for public recreation.


Why is there talk about removing or altering some of these dams?


Lowhead dams are effective at creating a volume or depth of water in the Ottawa River.  But they can obstruct the natural habitat in the stream bed, the movement of fish species living in the river, and create zones of lower oxygen levels in the impounded water areas.  The Ottawa River is home to 54 different species of fish, with many of them only being found upstream and downstream of the group of dams.  These structures therefore are a key limiting factor to the stream miles that are impaired and not meeting the state’s water quality standards.  The Ottawa River Coalition is engaged in a conversation about removal or modification of dams in ways that the river flow can be maintained but fish can naturally move into and survive in impaired areas.

The Ottawa River Coalition is championing the removal of the concrete dam in the Ottawa River, just north of State Route 81 in Allentown. The eighty five year old dam is no longer being used for the purpose it was created, and is a barrier to fish passage and water quality. The removal is planned for fall of 2020. Learn more about the removal of the Allentown Dam by downloading the flyer.



On October 16, 20018, Ohio Northern University’s field biology students conducted an assessment of the fish that live below the dam to gather data to be used in the planning for the dam’s removal. This video shows the wide variety of fish that they captured.

Ottawa River Coalition Fish Assessment at Allentown Dam

Eurasian Watermilfoil has been identified as growing in a dense mat in the Ottawa River in Lima over a mile long segment. It starts at the Lima Fire Station on Main Street and extends west or downstream, just beyond the Faurot Park footbridge. Local officials believe it has been growing here since at least 2016.  It does not normally grow in a flowing river, but the fact that it has established itself in between a series of lowhead dams is likely significant. As an invasive species, this plant has the ability to take over the native and diverse plant community in the river. The Coalition will continue to study the pros and cons of its presence in 2019.