The rocky bottom and strong currents of the river from the Fond du Lac Dam to the southern end of Nekuk Island provide good spawning habitat for walleye, lake sturgeon and other fish. Boating requires constant vigilance in this section of the river: fluctuating flows from a series of upstream dams combined with periodic water level changes caused by Lake Superior seiches bring underwater rocks and obstacles unpredictably close to the surface. This part of the river has been the site of an extensive sturgeon restoration project.

Over the course of the last century, however, fisheries of the estuary have faced great changes and serious challenges.  According to William Hearding's survey of 1861, the estuary coastline that now serves as docks and slips for large ships (700 ft salties to the 1000 ft lakers) was once a series of mud flats and shallows, with floating vegetation mats that would drift in and out of the harbor. This part of the lower estuary was biologically rich, providing an important spawning habitat for fish and supporting a rich bird and wildlife community.

The shoreline and coastal wetlands of the lower estuary changed dramatically as industrial development increased in the mid-20th century. Extensive areas of wetland were converted to docks, slips and industrial sites. The image below shows the shoreline William Hearding mapped in 1861 superimposed onto a 2009 air photo of the estuary. Prominent changes to the original coastline include the creation of numerous dock facilities in Wisconsin and Minnesota, the rail yard south of Rice's Point, and the creation of Erie Pier for storing materials dredged from the harbor.

In addition to loss of habitat, the estuary has been the site of heavy industrial contamination, such as the the Interlake/Duluth Tar site at Stryker Bay, where tar from the coke ovens, coal soot, and oil all eventually found their way into estuary sediments, severely limiting fish reproduction and making fish unsafe to eat.

Recovery: Restoration of fish habitat in the lower estuary

Considerable efforts are underway to restore fish and aquatic plant habitat in the lower estuary. The St. Louis River Habitat Plan, developed in 2002 identified several sites within the estuary with significant habitat limitations. Two sites in particular, the 21st and 40th Avenue West Habitat Complexes were identified as priorities for “remediation-to-restoration” projects. These sites have been the focus of an “ecological modeling and design” process, in which biological data (vegetation, sediment types, benthic macroinvertebrates, and bird usage) collected in the field were integrated with models of wind energy, bathymetry (bottom configuration) and other environmental data to develop a predictive model of aquatic vegetation. To assess restoration options, a diverse group of stakeholders, including state, federal, tribal, environmental and other interest groups, developed a set of restoration options. Scenarios include alterations to the bottom substrate or bathymetry to provide more suitable habitat for emergent, floating-leaf or submerged aquatic vegetation beds, along with the creation of islands or break walls to disrupt wind fetch and reduce wave energy. The ecological design model is being used to predict the types and areas of different aquatic vegetation beds to be established, along with the consequent improvement for macroinvertebrate, fish, and bird habitat. This ecological design tool will provide additional information to guide restoration activities within the estuary and ultimately further the removal of Beneficial Use Impairments from this Area of Concern.

Area of Concern

The lower St. Louis River and surrounding watershed were designated an "Area of Concern" (AOC) under the Great Lakes Water Quality Agreement in 1989 because of the presence of chemical contaminants, poor water quality, reduced fish and wildlife populations, and habitat loss. Among the Beneficial Use Impairments (BUIs) identified in the AOC are Loss of Fish and Wildlife Habitat, Degraded Fish and Wildlife Populations, and Degradation of Benthos. The St. Louis River Citizens Action Committee, now the St. Louis River Alliance (SLRA), was formed in 1996 to help meet the needs of the AOC. Following the recommendations of the St. Louis River AOC Stage II Remedial Action Plan, the SLRA completed the Lower St. Louis River Habitat Plan in 2002 as "an estuary-wide guide for resource management and conservation that would lead to adequate representation, function, and protection of ecological systems in the St. Louis River, so as to sustain biological productivity, native biodiversity, and ecological integrity."

Maps and Data

Water levels fluctuate throughout the year – View recent data from the Duluth Ship Canal.

As sediment settles out of water and onto the bottom of the estuary and the streams that flow into it, the small spaces between rocks and woody debris are filled in with mud and sand. Unfortunately, some of the insects that fish eat need those spaces to survive. Trout, which need a clean, gravelly stream bottom to spawn on, are also negatively affected when the sediment settles to the bottom. Additionally, the tiny particles of sediment can cover a fish's gills, making it difficult to breathe. Think about how difficult it would be to breathe during a dust storm.

As the estuary became an economic engine for the region because of its well-protected port and proximity to abundant natural resources, industrial activities grew, and along with this, so did the human population. As was the case in the early 20th century throughout the western world, rivers and harbors served as sewers for industrial and municipal wastes.  These organic wastes were food to the natural communities of bacteria, fungi, and small aquatic animals that ultimately decomposed most of it. Unfortunately, decomposition of the excess organic matter consumed oxygen dissolved in the water at a much higher rate than would have occurred naturally.  As more and more paper mill liquor, sawmill sludge, petroleum wastes, and human sewage was discharged, the oxygen consumption from this biodegradation eventually overwhelmed the processes that added oxygen back to the water (wind mixing and photosynthesis). The end result was very low levels of oxygen, sometimes approaching zero. This was especially true in summer, when river flows were lower (bringing in less oxygen-rich, flowing water) and water temperatures warmer (decomposition rates increase as temperature increases; warm water holds less dissolved oxygen than cold water).  Fish kills were common during these years, and the native invertebrate community (mayflies and dragonflies, for example) must have been largely eliminated, with the exception of a few hardy species.

A concerted clean-up effort paid off

Fortunately, by the 1970s the U.S. and some states (including Wisconsin and Minnesota) passed legislation to begin the long and expensive process of restoring degraded waterways, including the St. Louis River.  The first and most critical task was to address the numerous sources of organic matter finding their way into the river and harbor. About $100 million in federal funding was ultimately provided to create the Western Lake Superior Sanitary District (WLSSD). State-of-the-art wastewater collection and treatment facilities were built to consolidate 14 inadequately-treated discharges into one discharge point that met state and federal standards and provided additional pre-treatment for paper mill effluent.  Similarly, municipalities in Wisconsin discharging into the estuary have also upgraded their sewage treatment plants.

Water quality in the St. Louis River rapidly recovered after WLSSD came on-line in 1978, with dramatic increases in dissolved oxygen and greatly reduced levels of fecal coliform bacteria (an indicator of human feces) and many other parameters. This “story” can be viewed interactively by examining water quality data at many sites in the river over the period 1973-1996 using our dataviewer.

As sediment from eroding streambanks and stormwater runoff settles out of water and onto the bottom of the estuary and the streams that flow into it, the small spaces between rocks and woody debris are filled in with mud and sand. Unfortunately, some of the insects that fish eat require those spaces to survive. Trout, which need a clean, gravelly stream bottom on which to spawn, are also negatively affected when sediment settles to the bottom. Tiny sediment particles suspended in the water can cover a fish’s gills, making it difficult to “breathe,” just as a dust storm would make breathing difficult for us.  

The amount of suspended sediments in water can be measured in a variety of ways. The total weight of the suspended material in a known volume of water (total suspended solids or TSS) can be determined. A simple device known as a turbidity tube can be used to determine the clarity of the water. Finally, the turbidity, or cloudiness, of water can be determined by an electronic meter that measures how light passes through a water sample. The image below shows a range of turbidity, measured in units called Nephelometric Turbidity Units or NTUs.

Storm sewers bring more than water to the estuary

Knowing where the excess sediment is coming from helps us focus our restoration efforts. When it rains, the natural process of erosion carries sediment from land into the water. Because of this, sediment levels in streams are typically elevated during rainstorms. Unfortunately, when we build roads, houses, parking lots and other impervious surfaces, rain runs off the land faster and with more energy. Storm sewers and drainage ditches designed to direct water quickly off developed land to local streams and lakes during rain events increase the volume and velocity of water flowing downstream, often leading to increased stream bank erosion. The sand that is applied to winter roads can be washed into the estuary or surrounding streams via storm sewers. The type of soil in the watershed is also important. The red clay that dominates many of the watersheds on the Wisconsin side of the estuary is extremely susceptible to erosion.