Last week, I wrote about a new web resource created by the Minnesota Pollution Control Agency (MPCA) to share information about our state’s lakes, rivers, wetlands and groundwater with the public. Based on water monitoring data from around the state, the MPCA has found that the majority of lakes in northeastern Minnesota are healthy and clean, while the majority in southern and western Minnesota suffer from nutrient and sediment pollution. Not surprisingly, rivers and streams across the state mirror this trend as well.
Three-quarters of the streams and rivers in north and northeastern Minnesota support healthy aquatic life such as fish, amphibians, insects and mussels. This is because most still follow natural pathways, unlike many of the streams in the metro area and southern Minnesota that have been ditched to drain farm fields, straightened, and sometimes even buried underground. Also, though northern Minnesota was heavily logged in the past, 41% of the northwoods are once again woods, so there is less runoff pollution there than in urban and agricultural regions.
In the Twin Cities metro area, development has impacted most of the rivers and streams and only 37% are meeting water quality standards for aquatic life. Some streams in the urban core of Minneapolis and St. Paul have disappeared completely, replaced instead with underground stormwater pipes that convey rainwater from city streets directly to the Mississippi River. Within the inner ring suburbs, most of the streams support only a fraction of the fish species they once did, and chloride from road salt is a growing concern. The healthiest streams are those in the least developed areas, such as Valley Creek in Afton and a handful of small streams in northern Washington County that flow to the St. Croix River.
On the up side, there is less phosphorus, ammonia and bacteria in the Mississippi River than there was 75 years ago thanks to major improvements to waterwater treatment plants. Metro area rivers also have healthier levels of oxygen than they used to, allowing fish and other aquatic species to survive. According to the Mississippi State of the River Report, released by National Park Service and Friends of the Mississippi River in 2012, a 1926 survey found only two living fish in the 25 miles of the Mississippi south of St. Anthony Falls. Today, due to cleaner water and catch-and-release rules, populations of smallmouth bass, catfish, walleye and several other species of trophy fish are flourishing.
Stream and river health is worst in southern and western Minnesota where 78% of the land is agricultural. Most streams have been straightened and ditched and most large farms have installed underground drain tile to dry out the fields more quickly and create more farmable land. As a result, erosion and flooding are big problems, as are excess nitrogen and sediment in the water. Only 16% of the streams and rivers in southern and western Minnesota are healthy enough to support aquatic life. In addition, many streams have unhealthy levels of e. coli and fecal coliform bacteria, which can make people sick.
In Washington County, Brown’s Creek is a good example of a partially degraded stream that has improved in recent years due to targeted restoration work. The Brown’s Creek Watershed District has worked with private landowners along the creek, including Oak Glen Golf Course and Stillwater Country Club, to plant native habitat along the streambanks and install raingardens to capture runoff pollution. The district also completed two large stream improvement projects during construction of the new Brown’s Creek Trail. As a result, water in Brown’s Creek is cleaner and cooler and there are signs that trout may finally be reproducing in the creek again.