Lake Manawa IA 06-WEM-1711

Assessment Comments

Monitored in 1990 and 1992 by ISU as part of the Clean Lakes Classification study (1994) and also monitored in 1990 for fish tissue (RAFT sampling).

Basis for Assessment

Both fishable and swimmable uses were assessed as FST for the 1992 report for the following reasons:  (1) BPJ of DNR Fisheries; (2) average levels of total-P, chl-a, and TSS were better than overall averages for the 116 SPOLs sampled in 1990 and 1992 but were within 1 SD of the overall averages; the average level of secchi depth was worse than the overall average but was within 1 SD of the overall average; (2) lake does not have problems with fishkills with the exception of winterkills of shad in one of five years; (3) Bachmann et al.  (1994) report moderately high numbers for swimming use and very high numbers for fishing use; (4) lake has a relatively low sedimentation rate and relatively long life expectancy (613 years).   Low secchi depth not related to chl-a suggests a threat from turbidity; supplemental water is required to maintain lake levels; fishery apparently in good shape.