Walnut Creek IA 04-LDM-1069

Assessment Comments

Assessment is based on results of chemical and biological monitoring conducted as part of the Walnut Creek Watershed Resoration project from 1995-1997.

Basis for Assessment

SUMMARY:  The general uses of this stream remain assessed as "fully supported."  EXPLANATION:  This assessment is based on a review of the summary of water quality data from Schilling and Thompson (1999).   Approximately 30 samples were collected during water years 1996 and 1997 from each if the two mainstem sites on Walnut Creek (stations WNT1 and WNT2).   None of the levels of dissolved oxygen, pH, or ammonia-nitrogen in the  samples from these stations suggest the occurrence of acutely toxic conditions in this general use stream reach (although samples from one mainstem tributary site (WNT6) showed that levels of dissolved oxygen were at leasrt occasionally less than 4.0 mg/l).   Thus, despite indications of below average communities of fish and benthic macroinvertebrates (see Shilling and Thompson 1999, pages 43 and 47), results of water quality monitoring do not suggest any violations of general water quality criteria in Walnut Creek as described in the Iowa Water Quality Standards.   General use streams typically lack the flow stability and quality of aquatic habitats to support diverse aquatic communities.   The occurrence of environmentally tolerant forms of fish and aquatic macroinvertebrates in Walnut Creek is thus consistent with its classification only for "general uses."