The Minnesota Falls Dam played a vital role in Granite Falls’ past, facilitating local power generation for nearly 100 years. That particular role ended in 2004 when Xcel Energy curtailed operations at the Minnesota Valley Generating Plant, but the dam still fills a critical role in protecting the Minnesota River from invasive aquatic species, most notably the Asian carp.
The Asian carp is a prolific and destructive non-native species of fish that has invaded the waters of the Mississippi River as far north as Dubuque, Iowa, and is threatening to enter Lake Michigan through the Chicago Sanitary and Ship Canal.
Asian carp present a significant risk to native fish populations due to their voracious feeding habits and proclivity for habitat destruction. They also pose a safety hazard to recreational river users due to their size (commonly 10-15 pounds) and propensity for jumping out of the water into or over boats in response to outboard motors.
Asian carp are well established in the Mississippi River in the Quad Cities area of Iowa and significant numbers have been found in the waters north of Lock and Dam No. 11 near Dubuque, Iowa. Minnesota DNR records indicate that smaller numbers of Asian carp have been caught by commercial fishermen in the lower Mississippi River between Lake Pepin and the Iowa border, indicating continuing northward migration. Recent studies have identified Asian carp DNA in the Mississippi and St. Croix rivers near the Twin Cities and also in the Minnesota River near its confluence with the Mississippi.
The state of Minnesota has a variety of management strategies in effect to slow the spread of Asian carp to additional Minnesota waterways. These include prohibiting importation of Asian carp or any type of live baitfish, as well as prohibitions against the possession, sale, purchase or release of Asian carp.
In-stream behavioral barriers such as Sound Projector Arrays (SPA) and Bubble Acoustic Fish Fences (BAFF) are being evaluated for efficacy against Asian carp, but the most effective deterrents are physical barriers such as waterfalls and dams. Asian carp are able to navigate upstream against currents, rapids and the like, but dams and waterfalls are nearly 100 percent effective in preventing their upstream proliferation.
The Mississippi River has an expansive array of dams along its course. Unfortunately, most of these dams have been rendered ineffective against the spread of invasive species due to the system of locks which allows for passage of private and commercial vessels along the river. These navigational aids provide access to the Asian carp in the same way they provide access to boats, barges and other vessels.
According to a study prepared for the Minnesota DNR by FishPro Consulting Engineers and Scientists, the rate of upstream movement of Asian carp in major rivers of the United States is approximately 50 miles per year and populations can become established within two years after the first individual arrives.
Page 2 of 2 - With no existing physical barriers between the confluence of the Minnesota and Mississippi rivers and the Minnesota Falls Dam, Asian carp populations could conceivably reach our area in the next five to six years. The Granite Falls Dam may be the only reliable obstacle keeping these invaders out of the stretch of river running through Granite Falls.
There are many good reasons for retaining the Minnesota Falls Dam, but protecting the local river environment and ecosystem from this destructive species of fish may be paramount among them.