Within the urbanized areas of greater Duluth, 16 different cold water streams support trout populations. The most impaired of those, Miller Creek, is considered an early indicator of potential problems for the rest.
“It’s looked at as a canary in a coal mine,’’ said Tom Estabrooks, watershed manager in Duluth for the Minnesota Pollution Control Agency.
With trout numbers suffering in a developed stretch of Miller Creek, the MPCA is submitting a water quality report and fix-it blueprint for approval by the U.S. Environmental Protection Agency. If the EPA goes along, reforms could revive the fishery. The report is open for public comment until July 5.
“I think it’s a combination of improving the shading and improving stormwater treatment,’’ Estabrooks said.
Miller Creek is a trout stream that flows from near Duluth International Airport, through the cities of Hermantown and Duluth, past Miller Hill Mall and into St. Louis Bay of Lake Superior. The entire watershed is only 9.4 square miles, but it shares a rocky geology and other characteristics with the city’s better-known trout homes, such as the Lester River.
Recently listed by MPCA as temperature-impaired, Miller Creek has been hurt by development. It’s been robbed of tree shade and straightened in parts. Some of its water-cooling wetlands have been drained, and it’s now exposed to heavier, warmer rain runoff arriving from sewers that drain lots of impervious surfaces.
The excessive heat loads lower the oxygen levels needed for trout survival.
Estabrooks said Duluth area streams might be more susceptible to influences of real estate development because they rely heavily on overland water drainage. For instance, only 20 percent of Miller Creek’s water comes from underground sources compared with trout streams in other parts of state that are fed 80 percent by groundwater.
The draft report headed to EPA says Miller Creek is relatively sensitive to air temperature.
“This suggests that Miller Creek, and perhaps North Shore streams in general, may be particularly sensitive to climate change,’’ the report says.
Measures called for in the draft report include planting trees for shade, preserving and restoring wetlands, upgrading stormwater sewer systems and “re-meandering’’ parts of the stream that were straightened.
“We can help the system out before it gets too far down the road,’’ Estabrooks said.