Planter des arbres le long de la Nemadji River

Photo: Saint Louis River Citizens Action Committee

Le gouvernement fédéral des États-Unis est sérieux dans ses efforts d'assainir les Grands Lacs. Les affluents du Lac Supérieur, les rivières Midway et Nemadji serons aux petits soins cet été. $249,000 viendront du ministère de l'agriculture et seront utilisés par le ministère de conservation des ressources naturelles pour planter des arbres, surtout sur des terres privées à des endroits stratégiques afin de réduire les sédiments qui sont charriés par ces 2 rivières durant la fonte des neiges et à presque chaque ondée.

On veut reboiser les terres agricoles qui étaient originalement des forêts pour ralentir l'écoulement de l'eau et garder le sol en place. Difficile de ne pas voir le panache d'eau brunâtre qui sort de la rivière et se déverse dans le Lac Supérieur. Quand il pleut en amont, la Nemadji se sature de glaise et de sédiments venant des forêts, des terres agricoles et des rives érodées des ruisseaux.

Le U.S. Geological Survey dit que la rivière Nemadji charrie le plus haut taux de sédiments de tous les tributaires du Lac Supérieur des états du Minnesota et du Wisconsin: plus de 100,000 tonnes par année. Cette rivière draîne une région de 433 milles carrés, un sol de glaise et de sable laissé par la fonte du Lake Duluth durant l'aire glaciale.
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"Grant aims to reduce Nemadji’s red plume in Lake Superior

The federal government’s effort to clean up the Great Lakes will hit the Northland this summer with a reforestation effort miles away from Lake Superior. The U.S. Department of Agriculture this week(May 13) announced $249,000 for a project aimed at reducing the sediment that fouls the Midway and Nemadji rivers and pours into Lake Superior during snowmelt and after nearly every rain.

The Natural Resource Conservation Service will use the money to plant trees, mostly on private land, at key locations along the Nemadji and its tributaries. The government will pay 75 percent to 90 percent of the cost. Supporters say reforesting farmland that was originally cut from forests can change the hydrology of the area, slowing water down and keeping soil in place. Other efforts could pay farmers or landowners for projects that keep livestock out of streams and keep more grass on pastures to hold soil in place.

Anyone who looks out at Lake Superior from Duluth’s hillside can usually see the ruddy-brown plume into Lake Superior, through the Superior Entry, from the Nemadji River. When it rains across Carlton County, the Nemadji fills with clay and silt that runs off forests, farm fields and stream banks.

The stuff runs into creeks, streams and into the Nemadji itself and then dumps into Lake Superior through the Twin Ports Harbor. The U.S. Geological Survey says the Nemadji has the highest sediment load of any Lake Superior tributary in Minnesota or Wisconsin — more than 100,000 tons each year. That’s like backing up 23 dump trucks and unloading into the lake every day, all year.The Nemadji drains a huge, 433-square-mile area straddling the Minnesota-Wisconsin border south of Duluth, all the way into Pine County. The rolling hills and mix of farms and forests that make this area so appealing are the same qualities that contribute to the problem. The clay and sand, left by glacial Lake Duluth centuries ago, make a fragile base for an ecosystem much more prone to erosion than the nearby St. Louis River, which runs through more rocky and boggy country.

Water from rain and melting snow that was once absorbed by thick forests and wetlands along the Nemadji and its tributaries now flows quickly off fields, down roads and ditches and into streams overwhelmed by mini-floods. It wasn’t always like this. More than a century ago, the Nemadji and its tributaries ran much slower and clearer. The problem was created by intensive logging, farming, road construction and development."

Excerpts from article written by John Myers published here: http://www.duluthnewstribune.com/event/article/id/168575/

The Richelieu Valley, also blessed with rich soil, mostly clay left behind from the Champlain Sea a long long time ago, has seen its trees cut down to build European ships, forts, houses and barns, to make room for farmland and cities. Industries and most of the towns now treat their wastewaters, but agricultural fields have straightened ditches and streams and are now drained artificially, so that every rain brings tons of topsoil and whatever is sprayed on crops very quickly in watercourses, overfertilizing the aquatic domain and contaminating our drinking water. There is almost no forests left in the Richelieu Valley, and in my MRC, only 17% is covered with forests, and that number is mostly thanks to the few mountains that dot the scenery here and there...