Dissolved oxygen, water temperatures, Secchi depth, and surface drift
currents were measured in pool No. 2 of the Mississippi River during very
low flow conditions from August 24 through September 25, 1976 on eleven
different days and under significantly varied weather conditions. Water quality parameters were found to vary, both in time and space and in direct
relationship to prevailing weather, particularly wind and sunshine. With
total river flows from approximately 1000 to 2000 cfs, the measured D.O.
distributions, water temperatures, and transparencies were predominantly
typical of a series of interconnected lakes and to a lesser degree typical
of a river. Natural convection, density currents, and wind drift were found
to be of great importance. Recovery from low dissolved oxygen levels due
to the effluent from the Metropolitan Waste Treatment Plant occurred in the
pool upstream from Dam No. 2 mainly as the result of photosynthesis, surface
aeration, and the hydrodynamic exchange processes between different regions
of the pool.
Metropolitan Waste Control Commission St. Paul, Minnesota
Stefan, Heinz; Wood, Addison.
Field Investigations of Water Temperature Stratification and Wind Effects on Dissolved Oxygen in Pool No. 2 of the Mississippi River.
St. Anthony Falls Hydraulic Laboratory.
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