Based on years of observation it seems water pollution in the Dowagaic River Watershed isn't yet a problem. This conclusion has been aided by various reports that conclude the Dewey Lake, Cass County, Water Quality Survey. Those findings aren't forever though, so care needs to be taken to minimize damage from too much agricultural activity in the region.
There are three Dewey Lakes in three Cass Counties in the United States. This article deals with the Dewey Lake in Cass County, Michigan. The other locations are in Nebraska and Minnesota. This article reviews the findings of an informal Dewey Lake, Cass County, Water Quality Survey.
Dewey Lake is one of many lakes and ponds fed and drained by the Dowagaic River in southwestern Michigan. The Dowagaic River Watershed is a large river system covering 286 square miles including several tributaries, wetlands, and lakes. Dewey Lake is one of 23 lakes in the watershed that are 10 acres or more in surface area. All or part of 20 municipalities lie within the watershed.
Dewey Lake lies near the mouth of the Dowagaic River, in the Silver Creek sub-watershed. This sub-watershed is classified as a warm water fishery, while most of the entire Dowagaic Watershed is considered a cold water fishery.
The Dowagaic Watershed, including Dewey Lake, gets most of its water from underground infiltration of groundwater, rather than from surface runoff. This is because the soil in the watershed is highly permeable, so rainfall soaks into the soil and travels underground to the rivers and streams. Only 10 per cent of the Dowagaic Watershed's water flow comes from surface runoff.
Dewey Lake and the 22 other large lakes in the watershed are points of evaporative water loss. However, much of the evaporated water returns to the watershed in the form of rain. The Dowagaic Watershed receives an average of 21.66 inches of rainfall annually from April to September.
In 1991, the watershed near Dewey Lake was tested for pesticides and herbicides; none were found in the groundwater or surface waters. However, the groundwater level is relatively high in the Dowagaic Watershed, increasing its risk of contamination from pesticides, herbicides, fertilizers, and other agricultural chemicals.
Concerns have been raised about increased water consumption for agricultural, residential, and electrical power uses. At this time, not enough is known about groundwater supplies to know the threshold of water usage before it begins impacting surface waters, i. e., streams, rivers, and lakes such as Dewey Lake.
The lower Dowagaic River, including Dewey Lake, has been listed as a non-attainment area for water quality standards by the Michigan Department of Environmental Quality since 2000. The aquatic life in these lower sub-watersheds have been impaired. For example, PCB contamination has earned the lower Dowagaic a health advisory for carp. Arsenic has also been detected in the lower Dowagaic.
The Silver Creek sub-watershed, which includes Dewey Lake, was also listed in 2000 as a non-attainment area due to poor macro invertebrate counts, an indicator of poor water quality and/or lack of habitat. (Macro invertebrates include water beetles, mosquito larvae, caddis fly larvae, etc.) Silver Creek was dredged and straightened in 2002, making it an inappropriate site for biota data collection; so the non-attainment designation was lifted.
According to the Dewey Lake, Cass County, Michigan, Water Quality Survey, Dewey Lake and all of the Dowagaic River Watershed's surface waters are relatively pristine now. The Michigan Dept. of Environmental Quality is working closely with current residents and developers to ensure that this area remains a rich, valuable natural resource.
