Diamond Lake IA 03-NSK-861

Assessment Comments

Assessment is based on results of water quality monitoring and surveys of the DNR Fisheries Bureau.

Basis for Assessment

Fishable uses were assessed as FST for the following reasons: (1) results of monitoring in 1990 show that average levels of secchi depth, chl-a, total-P, and TSS are better than overall averages for the 116 SPOLs sampled in 1990 and 1992; (2) lake does not have problems with fishkills; (3) lake has a relatively low sedimentation rate and relatively long life expectancy (109 years) for an impoundment; (4) Bachmann et al.  (1994) report rel.  high numbers for fishing use; (5) DNR's 1994 fishing forecast in the "Iowa Conservationist" recommends Diamond Lake for bluegill, channel catfish, and crappie.   Lake is not designated for swimmable uses and Bachmann et al.  report swimming use as zero.   Sampling for 7 ag herbicides in Jan 1993 showed low levels of atrazine and cyanazine (both < 0.4 ug/l) in water; no detects in sediment.   WQ trend in stable (DSC 1991).