How Do Our Watersheds Become Impaired?

Turbidity!

About City of Superior’s Streams

Maybe you didn’t notice, but when you fell through the atmosphere as a raindrop, some of the dirt particles in the air got stuck to you (were you concentrating too hard on where you were going to fall?).  You only got dirtier when you picked up tar particles on the high school roof and sediment in the storm drain.  The problem with stormwater is it isn’t just rain – it also includes everything that goes into the water as it flows over paved surfaces -- this is what we call nonpoint source pollution. 

When it rains, stormwater…

Picks up pollutants in the air and on the ground

Enters the storm drain system

Goes straight to the stream

Photo Source: Wisconsin DNR

The EPA lists nonpoint source pollution as the
number one threat to water quality in the nation.

When stormwater falls on developed areas with lots of impervious surfaces (e.g., roofs, parking lots, and roads), it cannot soak into the ground, where soil particles filter out pollutants and slowly allow groundwater to enter nearby streams.  Instead, the water washes into storm drains, taking along with it any pollution it has picked up along the way. Most storm drains are not connected to the wastewater treatment plant, which means stormwater exits the storm drain at the nearest stream, often at high velocity.  In the City of Superior, this high-velocity water erodes red clay into the City’s streams.  Nonpoint source pollution loadings from storm events can have a greater effect on streams than point source discharges.  

Some of the stormwater effects in Superior include:

h     Flooding

h     High bacteria levels on local beaches

h     Erosion

h     Increased water temperature

h     High turbidity (murky water)

h     Water pollution from oil

Dump No Waste, Drains to Lake: This is the message that elementary students stenciled on storm drains throughout the City of Superior in 2006.  Click HERE to see their work!

As impervious surface increases, we see these effects on streams:

h     Channel becomes straighter

h     Channel becomes shallower

h     Channel slope becomes steeper

h     Higher stream velocities

h     Increased sediment load

h     Decreased ability to support aquatic life

h     Channel enlargement

h     Stream incision

h     Decreased ability to support aquatic life

(From the Center for Watershed Protection)

To learn more about the effects of impervious surface, click HERE.

The ultimate consequence of urbanization: Faxon Creek’s banks are lined with brick to prevent erosion.

Help prevent stormwater pollution by following these suggestions!

h     The number one thing: pick up after your pets!  Every year, the City of Duluth removes 3 truckloads of pet waste from its waterfront.  All those dogs add up to a lot of waste!

h     Eliminate or reduce your use of fertilizers and pesticides.  If you need to use them, make sure you apply them properly and sparingly.

h     Purchase household and garden products that are “least toxic” to the environment. 

h     Sweep up debris such as sand and leaves from driveways and curbs; otherwise, this debris washes directly into Lake Superior and pollutes it.

h     NEVER dump motor oil or anything else down storm drains.

h     Wash your car on the lawn or at a carwash instead of on the driveway.

h     Make sure your vehicle isn’t leaking fluids like oil, antifreeze, and gas.

h     Rural homeowners: make sure to have your septic tank pumped regularly.

h     Don’t litter!  A good rain shower washes trash (like cigarette butts and hundreds of drinking straws) into our lakes!

h     Consider using a rain barrel or planting a rain garden.

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Turbidity!

A cloud of fine sediment obscures the water whenever the streambanks are disturbed.

Turbidity is defined by how cloudy or murky the water is.  All of the streams and tributaries in the City flow through red clay deposits that cause the water to be naturally murky.  Though this sediment is geologically young and highly erodible, core samples taken on the St. Louis River by Minnesota Sea Grant show that sedimentation rates have been accelerating since the early 1900s.  High flows related to stormwater runoff cause slump erosion along many of the City’s streams.  This is especially problematic when the riparian buffer zone alongside streams is removed because rooted plants slow water flowing into the stream and hold stream banks in place.  The Nemadji River alone transports an annual sediment load of 280,000 metric tons into Lake Superior (SLRCAC).  The sediment plume caused by the Nemadji River extends as far as 15 miles into Lake Superior.  The EPA lists suspended sediment as the number one impairment to water quality in streams and rivers.

Problems caused by high turbidity:

h     Suspended sediment blocks sunlight, which is required for aquatic plant survival.

h     Sediment smothers the spaces between rocks in the stream bottom, which is prime habitat for fish eggs and aquatic insects. 

h     Fish have a harder time locating food, breathing through their gills, or finding mates based on visual cues. 

h     Turbidity also affects the aesthetic qualities of a water body, and people are less likely to fish or swim in murky water. 

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About City of Superior Streams

A kayaker paddling up from the mouths of any of Superior’s streams would not get very far, and it would be very difficult to turn around for the return journey!  Though the City’s streams are wide and slow-flowing where they meet Lake Superior, their upstream reaches are shallow, narrow, and intermittently filled with water.  Because the City of Superior is underlain by relatively impermeable clay, surface water infiltration to groundwater is negligible.  Therefore, the City’s streams are mostly fed by overland flow coming from stormwater, which means baseflow is very low during dry periods.

Several of Superior’s streams are on the Section 303d List for impaired waters under the Clean Water Act.  Hog Island Inlet, Newton Creek, and the Nemadji River are listed for mercury, and the Nemadji is also listed for turbidity.  Lake Superior and all tributaries to the first impassable barrier are also listed for turbidity.  In addition, all of the waterways in Superior are part of the St. Louis River Area of Concern, a designation based on a number of beneficial use impairments, such as fishing, turbidity, and habitat loss.  All the streams in Superior have also been designated as Areas of Special Natural Resources Interest.

Seiche events can increase water levels on Superior’s streams; sometimes the streams will even flow backwards!  A seiche occurs when water from Lake Superior is pushed by wind action up against the south shore, filling the river mouths with lake water. 

The Nemadji River and the Pokegama River are the largest drainages in Superior, and the Nemadji River is the only waterway that is navigable in its upper reaches.  All of Superior’s streams originate in Wisconsin, except for the Nemadji River and Pokegama River, which have their headwaters in Minnesota.

Faxon Creek: narrow, shallow, and colored with red clay, like most of Superior’s streams.

From the St. Louis River Habitat Plan:

[Clay-influenced tributaries] were identified as targets as part of the Great Lakes aquatic eco-regional planning process. They include tributaries such as the Red River and Little Pokegama River, as well as the larger Nemadji River. Bluff Creek and Bear Creek are also included in this habitat type. They are defined by a broader set of physical characteristics than the other estuarine aquatic habitats. Their health is determined in part by their own hydrologic regime, not by Lake Superior or the St. Louis River. They are first- or second-order, medium- to low-gradient, groundwater- and surface water-influenced streams, flowing through lacustrine red clay deposits. These tributaries provide habitat for a variety of the native fish found in the estuary.  Ditches, wetland draining, and other hydrologic modifications in the watersheds have altered the surface water hydrology of these streams. Changes in the com­position of the surrounding forest have resulted in excessively high flows and extremely low flows, which in turn cause excessive streambank erosion, increased sedimentation, and habitat impairment. Ditching and developed areas create higher peak flows and increased sediment loads in these streams.

To take a virtual tour of Superior’s streams, click HERE.

Superior’s streams are all part of a watershed: this ditch may not look like much, but it drains to Bluff Creek and Lake Superior, so anything that washes into this ditch can pollute the lake.

Photo Source: CTE Superior, Wisconsin Surface Water Management Plan

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Back to “A Raindrop’s Journey”

Back to “A Virtual Tour of Superior’s Streams”

Back to “Charting the Course to Stream Health”

Website Created by Kari Hedin, 2007