On Interstate 80/90 in Ohio there is a small, unassuming sign that indicates you have crossed the line that divides the Great Lakes basin and the Mississippi River basin.
Keeping these two watersheds separate is important for the health of both water systems, but that dividing line is not stopping water and fish from moving between the basins.
The Great Lakes Mississippi River Interbasin Study (GLMRIS) indicates that a water exchange between basins (hydrological risk) could occur through wetlands, ancient portage routes, rivers and streams during high water events or floods. This could allow non-native organisms, known as Aquatic Nuisance Species (ANS) to displace native species and degrade native habitats.
View Larger Map. This map is based on the GLMRIS Other Pathways Preliminary Risk Characterization which was completed in 2010. Updated H&H ratings and biological assessments will be presented in the Other Aquatic Pathways Risk Characterization Report expected for release in spring 2012.
This study by the U.S. Army Corps of Engineers in consultation with federal, state and local governments, Native American tribes, and non-governmental organizations has identified two focus areas, the Chicago Area Waterway System, and potential pathway locations along the Great Lakes/Mississippi River divide.
Information about steps being taken in the Chicago Area Waterway System to deal with ANS and hydrological issues can be found in the Asian Carp: Threat to Great Lakes video.
GLMRIS is focusing on eighteen locations along the Great Lakes/Mississippi River basin that require further study.
Of these locations, the area that elicits the most concern is Eagle Marsh in Ft. Wayne, Indiana. In 2010, an 8 foot high, 1,200-foot long mesh fence was erected to keep fish from transferring between the Great Lakes basin and the Mississippi River basin. The depth of the water during a heavy rain or a flood at Eagle Marsh can be significant enough that without the fence, fish could swim from one basin into the other.
This map indicates the level of concern of hydrological risk at the GLMRIS identified locations. The red water icon represents areas where the conditions are ideal, very favorable or favorable for the water to flow from one basin to the other. The orange water icon represents places where it’s possible and the yellow water icon shows where it is unlikely or highly unlikely that the water will move from one basin to the other.
The ANS ratings that the invasive species can cross the basins for these locations are:
- red fish icon–acute or high probability
- orange fish icon–medium
- yellow fish icon–low probability
The invasive fish currently residing in the Mississippi River and its tributaries are:
The invasive fish currently residing in the Great Lakes are:
The goal is to keep each of these species from migrating from one basin to the other.