Blackbird Bend IA 06-WEM-1732

Assessment Comments

Assessment remains based on (1) information from the IDNR Wildlife Bureau and (2) results of watershed modeling by the IDNR Water Quality Bureau.

Basis for Assessment

SUMMARY:  The Class B(LW) aquatic life uses remain assessed (evaluated) as "not supported" based on information from the IDNR Wildlife Bureau.   This assessment is also based on results of watershed modeling by the IDNR Water Quality Bureau in 2002.   Fish consumption uses remain "not assessed."  This assessment is the same as that developed for previous assessment/listing cycles.  Note:  this assessment has not been updated following the severe flooding of the Missouri River during summer 2011 and thus does not reflect flood-related changes that may have occurred at this floodplain wetland.

EXPLANATION:  The Class B(LW) aquatic life uses remain assessed as "not supported" (IR Category 3b) based on information from the Iowa DNR Wildlife Bureau (see assessments developed for the 1998 and 2000 reporting cycles).   Blackbird Bend, however, is part of an Army Corps of Engineers mitigation project along the Missouri River; this project will result in water being pumped into the wetland thus correcting, or at least mitigating, the flow alteration impairment.   Watershed modeling completed by the IDNR Water Quality Bureau in 2002 for Blackbird Bend indicates that sediment delivery to this wetland from the watershed is very low.   The local DNR biologist indicates that the Missouri River does not breach the original high bank, but occasionally (10 -15 years) flood waters do enter the wetlands directly adjacent to the river.   An updated assessment for this wetland will be needed following completion of the mitigation project.  

The assessment category for this wetland of "evaluated" indicates that the assessment is based entirely on "best professional judgment."  In terms of Section 305(b) reporting, "monitored assessments" are based primarily on recent, site-specific ambient monitoring data and thus have relatively high confidence.   IDNR considers waterbodies identified as "impaired" based on "monitored assessments" as candidates for the state's Section 303(d) list.   "Evaluated assessments" are those based on data older than five years or other than site-specific ambient monitoring data (e.g., desktop modeling or questionnaire surveys of fish and game biologists [=best professional judgment]) and thus have relatively lower confidence.   IDNR does not consider waterbodies identified as "impaired" based on "evaluated assessments" as candidates for the state's Section 303(d) list.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this wetland.   In general, Iowa wetlands are not managed for recreational fisheries; thus, fish contaminant monitoring is not typically conducted at these waterbodies.