Hawthorn Lake IA 03-NSK-862

Assessment Comments

Assessment is based on results of water quality monitoring and surveys by IDNR Fisheries Bureau.

Basis for Assessment

Bachmann et al.  (1994) show that the lake is not used for swimming; thus swimmable uses were not assessed.   Fishable uses were assessed as FST for the following reasons: (1) BPJ of DNR Fisheries; (2) results of monitoring in 1992 show that average levels of secchi depth and chl-a are approx equal to overall averages for the 116 SPOLs sampled in 1990 and 1992; average levels of total-P and TSS are better than overall averages.   Thus, lake has average to above average WQ; (3) according to Bachmann et al.  (1994), lake has a relatively low sedimentation rate (1.4 cm/yr) and long life expectancy (271 years) for an impoundment in southern Iowa; (4) lake does not have problems with fishkills.   According to DSC, sediment and nutrient delivery to the lake in NPSP, while not excessive, is the major source of pollution.