The concern about development having negative impacts on local trout streams is not unfounded. The Twin Cities area once boasted numerous trout streams, most of which have now been totally lost or degraded beyond reclamation. To prevent the loss of another beautiful midwestern trout stream to the hands of development, a temperature-monitoring project was undertaken by the Kiap-TU-Wish Chapter of Trout Unlimited in 1992. The goal of these efforts was to document the effect that stormwater runoff had on the temperature and composition of the stream.
Indirectly affected by their food source
While trout may be able to survive certain fluctuations in temperature, the food they rely on, mainly aquatic insects, may not. A Maryland study determined that many coldwater insect species would be eliminated or reduced by the thermal enrichment of a stream. Important species to the trout, such as stoneflies, mayflies, and caddisflies, would be severely impacted or stressed by stream temperature fluctuations. Thus stream temperature fluctuations have not only the potential to stress the trout directly, but indirectly through their food source as well.
The results of the monitoring project suggest numerous ramifications of development for the Kinnickinnic watershed. The drastic temperature spikes recorded during rain events suggest that the percentage of impervious surfaces in the watershed has already begun to affect the stream. The higher baseline temperatures of the stream at the Lower Glen Park station compared to those at the Quarry Road and Cedar Street imply impacts of urbanization as well.
|| The Kinni is designated an “Outstanding Resource Water” by the Wisconsin Legislature – the highest classification possible.
The implications of the findings for aquatic life, specifically trout and the insects they eat, in the Kinnickinnic watershed are similar to those found in the Maryland study. As stream temperatures increase beyond the preferred range for trout, the stress on the fish will increase accordingly. Temperature spikes upwards of ten degrees, like those witnessed in a typical storm event at the Cedar Street monitoring station, coupled with increased average baseline temperatures could easily push stream temperatures towards the upper lethal limit of 77º F for trout. These temperature spikes could also have detrimental effects on resident insect populations as well. Temperature fluctuations in the Kinnickinnic’s temperature could potentially reduce or eliminate certain temperature sensitive insect species such as the stoneflies, caddisflies, and mayflies. Given that these insects are a main staple of a trout’s diet, their elimination would mean severe consequences for the trout of the Kinnickinnic. The result of these effects could ultimately mean reduction or even destruction of the Kinnickinnic’s trout population.
Successful steps taken
The Kiap-TU-Wish’s stormwater monitoring project has been a great success. Designed to assess the impacts of urban stormwater runoff on the Kinnickinnic River, the project’s stream temperature monitoring and stormwater quality assessment resulted in a clear picture of these consequences. Temperature spikes during storm events and median concentrations of suspend solids above those recommended by the NURP suggested that the urban development had already begun to affect the watershed. Although the River’s trout populations were strong, the potential existed for the degradation of stream quality with severe implications for aquatic life.
Once the extent of the impacts of development on the Kinnickinnic watershed was known, steps could be taken to ensure protection of the River and its trout. Through the WDNR priority watershed program and the Kinnickinnic River Water Management Plan, the growth of River Falls and development of the land in the River’s watershed will be monitored and controlled. The end result should be the preservation of water quality and aquatic life in the Kinnickinnic River.
Committed to conservation
Thanks to the efforts of Kiap-TU-Wish, their partners, and commitment to conservation, the Kinnickinnic watershed may not fall victim to urbanization like so many of its neighboring counterparts. Its currently healthy population of brown trout should sustain itself and the Kinnickinnic will retain its reputation as a first-rate trout stream. As long as guidelines for development are considered and water quality is protected, the pristine waters of the Kinnickinnic River will be available for all to enjoy.