Stories tagged saint croix


The issue:
About a month ago, a frack-sand mining operation near Grantsburg, WI, spilled some fine-grained sediment from a settling pond into a tributary of the St. Croix River. Local news media covered the story, and more details, for example, can be found in the Pioneer Press story by Dennis Lien.

So what’s the big deal?
Well, there are standards regarding water turbidity, which means that as a society we’ve decided that we don’t like cloudy water, at least in some settings and at some levels. For a naturally clear-water system like the St. Croix, increasing turbidity would alter the food chain at all levels. Algal primary producers rely on sunlight blocked by turbidity. Sight-based predation at the top of the food change would be altered. Benthic (bottom-dwelling) organisms that depend on coarse substrates could be smothered by siltation. Especially in the St. Croix, one of the last refugia for freshwater endangered mussel species, we must be on guard against too much fine sediment. And finally, where does the sediment end up? It’s filling up not only man-made reservoirs but also treasured natural lakes, iconically Lake St. Croix and Lake Pepin. These lakes are filling in with fine-grained sediment at about 3X and 10X their natural rates, respectively. (How do we know? See work done by the Museum’s St. Croix Watershed Research Station.)

Hey, it’s only a little bit...
Or was it? How much is a little? A little here, a little there, and a little more from over there -- it starts to add up. All water in a watershed runs downhill to the river, efficiently carrying both particles and dissolved materials. The river ultimately sees it all: all the disturbances, however seemingly minor, throughout the watershed. Rivers die a death of a thousand cuts. We have enough difficulty trying to control nonpoint sources of sediment and other pollutants. Stopping discharge of fine-grained materials from a mining operation is eminently fixable. It’s the right thing to do. Fortunately, all parties seem in agreement on this, including the mining company, which has repaired its leaky dike.


Grass Carp: Grass Carp (White Amur) - Ctenopharyngodon idella Courtesy USGS

Grass carp, which sound like the kind of fish you would find in Cheech and Chong’s aquarium, have been turning up in the rivers around Minnesota. And authorities aren’t excited by the possibilities of this invasive species making a home in northern waters.

In early April, a commercial fisherman caught a 45- to 50-pound grass carp in the St. Croix River near Prescott, Wisc. While it was a thrilling fish to pull in for the angler, it does raise concerns about the changing dynamics of the fish population in the Mississippi River and its tributaries.

The grass carp is one of three reported catches in the Minnesota/Wisconsin river in the past two years. The others came in the past two falls, with one being caught in Lake Pepin on the Mississippi River and the other caught further downstream near the southern Minnesota border. While the Minnesota Department of Natural Resources is concerned about these intruders, it hasn’t found any evidence that they’re breeding yet in northern waters which would accelerate their numbers.


On April 6, officials from Minnesota and Wisconsin signed an agreement designed to reduce levels of phosphorus in the St. Croix River by 20% by the year 2020.

For more information about phosphorus in the St. Croix visit the Buzz kiosk in the Mississippi River Gallery on level 5, or check out our on-line feature.