Fishing

Green Lake Watershed Assessment

Project Description

Green Lake in Allegan County currently supports a strong cisco population and is one of a small number of healthy cisco lakes remaining in Michigan. However, nutrient runoff from agricultural land (52% of the watershed) and urban land (42% of the shore land) is a concern. The Michigan Department of Natural Resources has identified Green Lake as a conservation priority because of its high water quality, the presence of cisco, and vulnerability to human disturbances. This project aims to assess the health of the lake and its catchment area, invest community members in water quality monitoring, create nutrient budget for the lake, and create a lake management plan. After this assessment, best management practices (BMPs) can be implemented to maintain a healthy cisco habitat, Green Lake’s aesthetic values, and recreational opportunities.

This project is funded by the Fisheries Habitat Grant Program (FHGP) through the Michigan Department of Natural Resources. FHGP supports conservation activities to protect fisheries, aquatic resources, and the public. Inherently, the activities carried through this grant will conserve fish and aquatic species habitat, increase the quality of lake-based recreation, and preserve the health of our local waters. Allegan Conservation District was granted funds to support Green Lake because of our need to protect the cisco population that inhabits the water. While Green Lake is one of the few remaining healthy cisco lakes in Michigan, it is under threat due to urban development near the lakeshore, nutrient runoff from agricultural land, and warming of the surface water temperature due to climate change.

Purpose and Background

Why is it important to protect Cisco?

Cisco are native to the Great Lakes and to inland lakes of Michigan, weaving them into our local economy, recreational activities, and aquatic ecosystems. While Cisco are desirable to recreational and commercial fishers, they are also essential to the diet of other native fish species. Since Cisco require cold, deep lakes with high water quality and well-oxygenated water, they can serve as an indicator to let scientists know when water quality in a lake is degrading. In other words, if Cisco are present, the ecosystem and water quality of the lake is likely healthy, but if Cisco populations are dropping, that is an indicator of low water quality. This lower water quality can also impact native species such as northern pike and largemouth bass who may depend on Cisco for food. Protecting Cisco means we can protect entire ecosystems.

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Cisco - Photo courtesy of Michigan Sea Grant.

Why are Runoff and Climate Change Threats?

Agricultural nutrient runoff poses threats to all watersheds in Allegan county. Commonly used fertilizers, especially ones that contain phosphorus and nitrogen, are needed for plant growth on our farms, but they also support unwanted plant growth when they are carried by runoff into bodies of water. This causes an excess of nutrients in our waters, a process called eutrophication. A primary concern with eutrophication is how it can cause algae blooms in lakes. Algae blooms are a host for several further problems - decreased levels of dissolved oxygen in the water, release of harmful toxins, outcompeting beneficial plants that animals feed on, degraded fish habitat, and decreased quality of recreational activities. Additionally, sediment runoff from farmlands and urban areas increases the turbidity of the water, which again, decreases the water quality needed to sustain aquatic life. The problems caused by runoff affect water at all depths, but depending on the scenario, can affect the health of lake bottoms - thus, forcing fish populations to move closer to the water surface to find better water quality.

 

While runoff is causing problems on the bottom of the lakes, climate change is posing threats from the surface. Some fish species, especially Cisco, prefer to live in cool waters – so as water temperatures rise due to climate change, fish begin to search for the colder water found at deeper lake depths. This movement of fish can cause drastic changes in aquatic ecosystems. In tandem, the threats of runoff and climate change are essentially “sandwiching” aquatic species into smaller habitats in middle lake depths.

How We Are Stepping In

For now, Green Lake is still sustaining a healthy ecosystem, but the Department of Natural Resources has identified Green Lake as a conservation priority. The Allegan Conservation District is teaming up with local volunteers to assess the severity of current sources of sediment and nutrient pollution. This initial assessment will allow us to develop a nutrient budget that will protect Green Lake’s health. After the assessment is complete, we will work with partners to develop Best Management Practices (BMPs) and a Green Lake Watershed Management Plan. The implementation of our management plan and best practices will serve to protect Green Lake before essential ecosystems are permanently damaged.

Get Involved!

We are recruiting volunteers from the community to assist with data collection! We believe hands-on community engagement will encourage more locals to share an interest in water quality management and watershed protection. We offer training events so you can be prepared to assess water accurately and effectively. Contact our Executive Director, Brian Talsma, to get involved!