This report describes hydro-thermal models developed to simulate temperature mitigation of
surface runoff for wetland basins. Two models are described: 1) a dead zone model, which is a
modification of the previously developed vegetated pond model to include flow short circuiting
and 2) a new, multi-cell model that attempts to model lateral temperature gradients between a
short-circuiting channel and a wetland basin. Both models predict that a well-vegetated wetland
basin can provide substantial thermal mitigation. The dead zone model is used in conjunction
with a model for a wet pond to simulate the response of a wetland complex to stormwater inflow
for 6 years of observed storm events. The wetland complex was found to reduce runoff
temperature by 2.6 °C, on average for Minnesota climate conditions, compared to unmitigated
runoff from an asphalt parking lot. The wetland complex did not, however, reduce the average
runoff temperature for all storms. During very warm weather following storm events, the
wetland outflow temperature did exceed 20 °C for periods of up to several days.
Vermillion River Watershed Joint Powers Organization; Minnesota Pollution Control Agency
Herb, William; Mohseni, Omid; Stefan, Heinz.
A Model for Mitigation of Surface Runoff Temperatures by a Wetland Basin and a Wetland Complex.
St. Anthony Falls Laboratory.
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