Holland Lake, a small but deep mesotrophic lake in the Twin Cities Metropolitan
Area, has been considered by the Minnesota Department of Natural Resources, Division
of Fisheries, for stocking with brown trout. Holland Lake, with a surface area of 0.14
km2 (35 acres) and a maximum depth of about 18.8 m (61 ft) consists of two shallow
bays covered with rooted macrophytes and a deep main basin. The deep basin is
thennally suitable for brown trout. However, due to a high oxygen depletion rate in
summer, the lake becomes anoxic below the surface mixed layer from late June to early
July. The rate of oxygen depletion below the surface mixed layer, based on field
measurements, was estimated to be about 0.47 mg/day·l. Field studies conducted in the
summers of 1999 and 2000 indicated that only horizontal advection processes could
explain the observed high dissolved oxygen (DO) depletion rates. Density currents
transport low DO water with high BOD into the deep basin metalimnion. These currents
from the shallow bays were attributed to the temperature regimes of the shallow bays and
groundwater flow through the lake.
To improve brown trout habitat in Holland Lake, an aeration system has been
designed based on the observed sumnler conditions. The aeration system comprises two
bubble curtains along the border of the shallow bays to enhance mixing in the shallow
bays and one metalimnetic aerator in the deep basin. The bubble curtains deepen the
surface mixed layer down to 4 m, and prevent the fomlation of density currents from the
shallow bays into the deep basin.
Metro Region Fisheries, Minnesota Department of Natural Resources
Mohseni, Omid; Graske, Greg; Donovan, Richard; Stone, Mark; Fleming, Ryan; Stefan, Heinz G..
Design of an Aeration System to Enhance Trout Habitat in Holland Lake, MN.
St. Anthony Falls Laboratory.
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.