Black Hawk Lake IA 04-RAC-1134

Assessment Comments

Monitored in 1990 by ISU for the Clean Lakes Classification study (1994); monitored for 1992 RAFT.

Basis for Assessment

Both fishable and swimmable uses were assessed as FST for the following reasons:  (1) BPJ of DNR Fisheries; (2) results of monitoring show that average levels of secchi depth, chl-a, total-P, and TSS are either approximately equal to or worse than overall averages for the 23 SPO natural lakes sampled in 1990 and 1992; all parameters are within +/- 1 SD of the overall averages.   Lake has moderately high sedimentation rate for a natural SPOL and has a relatively short life expectancy (213 years); thus, lake is threatened by sediment from agricultural runoff.  All contaminants analyzed for in samples of carp collected for the 1992 RAFT were < 1/2 the FDA action levels.   According to Bachmann et al., the lake supports an average amount of swimming and fishing for a natural SPOL in Iowa.   FS also threatened by plankton, algae, organic enrichment, and turbidity related to natural shallowness.