Lanterna Rally

Author: Dennis E. Ford

Publisher:

Published: 1977

Total Pages: 82

ISBN-13:

The water quality of the proposed LaFarge Lake, Wisconsin, was investigated for a lower pool elevation (250.5 m MSL) using a version of the reservoir portion of the Water Quality for River-Reservoir Systems (WQRRS) ecological model. As in a previous study at a higher elevation (256 m MSL), the effort concentrated on temperature, dissolved oxygen, and algae. All model coefficients from the previous study were retained with the exception of Secchi disk depth, which was reduced from 3 to 2 m to account for probable increased turbidity at the lower pool elevation. The simulations indicated that LaFarge Lake would be a dynamic impoundment at the lower pool elevation. Temperature stratification was weak and intermittent. Dissolved oxygen was distributed throughout the pool during periods of complete mixing and was rapidly depleted in the hypolimnion during periods of stratification. A bloom of diatoms and green algae during the spring and at least two major blooms of blue-green algae during summer and fall were predicted. The phasing of these blooms was similar to that found at the higher elevation, but the two blue-green algae blooms increased in magnitude at the lower pool level. Coliforms were found to persist longer and to be distributed throughout more of the pool at the lower elevation. The phosphorus loadings at the lower pool elevation were approximately twice as large, but since the flushing rate was increased approximately three times, the eutrophication potentials of the two pool levels, based on Vollenweider's loading curves, were similar. It was not possible to meet downstream temperature objectives for a cold-water fishery. (Author).