Blencoe Lake IA 06-WEM-1724
Monona County S25T82NR46W 5 mi. SW of Blencoe
- Cycle
- 2020
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trend
- Unknown
- Created
- 9/9/2020 10:36:25 AM
- Updated
- 10/16/2020 7:54:11 AM
The Class BLW uses remain assessed (evaluated) as "not supported" (IR Category 4c) due to hydrological modifications (flow alterations and channel degradation of the Missouri River) that adversely affect this wetland. This type of impairment is appropriate for Category 4c of Iowa's Integrated Report (i.e., impairment due to a non-pollutant stressor). All other designated uses are “not assessed.” This assessment is the same as that developed for previous assessment/listing cycles.
Class BLW - The Class BLW aquatic life uses remain assessed as "not supported" due to impacts of hydrological modification of the Missouri River and resultant problems with water level fluctuation in the river's floodplain wetlands (see assessments developed for previous reporting cycles). Watershed modeling completed on Blencoe Lake in 2002 indicates that sediment delivery to the wetland from the watershed is very low. In addition, 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 wetlands such as Blencoe Lake that are adjacent to the river. Based on this information, the previous identification of "siltation" as impairing the aquatic life uses of this wetland was in error. The impact from hydrologic modification of the Missouri River, and the related problems with maintaining adequate water levels in this riverine wetland, remain. Class HH - Fish Tissue sampling: No Data In general, Iowa wetlands are not managed for recreational fisheries; thus, fish contaminant monitoring is not typically conducted at these waterbodies. 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.
The assessment category for this wetland is "evaluated."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. DNR 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 models or questionnaire surveys of fish and game biologists [=best professional judgment]) and thus have relatively lower confidence. DNR does not consider waterbodies identified as "impaired" based on "evaluated assessments" as candidates for the state's Section 303(d) list.
None listed