East Fork Wapsipinicon River IA 01-WPS-409
from the Bremer/Chickasaw county line (N line S3 T93N R12W Bremer Co.) to confluence with unnamed tributary in SW 1/4 S6 T94N R11W Chickasaw Co.
- Assessment Cycle
- 2016
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 3 - Insufficient data exist to determine whether any designated uses are met.
- Trend
- Unknown
- Created
- 7/14/2016 1:56:41 PM
- Updated
- 12/19/2016 1:29:20 PM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2012 | Class BWW2 | Fish Kill: Cause Unknown | Biological monitoring: Iowa DNR fish kill follow-up | New data: recovery of fish community from pollutant-caused fish kill |
The presumptive Class A1 (primary contact recreation) uses remain “not assessed” (IR 3a) due to lack of information upon which to base an assessment. The assessment of support of the Class B(WW2) aquatic life uses is changed from “not supporting” (IR Category 5b) due to a June 2011 fish kill to “not assessed” (IR 3a). This change is based on results of fish kill follow-up monitoring conducted by IDNR staff in August 2015. This change represents a de-listing of the biological (fish kill) impairment.
The kill occurred on or before August 20, 2008. The kill killed 76,292 fish along 2.5 miles of the East Fork of the Wapsipinicon River. The value of the fish was estimated to be $40,053.15. No cause for the kill was identified. Water samples were collected at the time of the kill that ruled out livestock manure as the source of the kill.
According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Due, however, to the extremely large number of fish killed (~75,000), the length of the kill (2.5 miles), and the lack of environmental extremes during summer 2008 that would have contributed to this kill (e.g., low stream flow and/or high water temperatures), some type of pollutant cause is suspected. Thus, this assessment was moved from Category 3b of Iowa's 2010 Integrated Report (potentially impaired) to IR Category 5b (impaired) of the 2012 IR.
This stream segment’s fish community was sampled on August 4, 2015, as part of the IDNR Watershed Improvement and Water Quality Monitoring & Assessment sections’ fishkill follow up monitoring program. Sampling methods described in IDNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s 2016 assessment/listing methodology) were followed. Approximately 700 feet of stream were sampled using a single pass with two backpack electro fishing units. Results of this sampling show that this stream supports approximately 4,250 fish per mile compared to the Level IV ecoregion 47c average of approximately 3,900 fish per mile; 82% of the expected fish taxa for this ecoregion were sampled. For detailed results of this sampling, see https://programs.iowadnr.gov/bionet/Sites/1043. The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams. Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from the August 2008 fish kill event. Thus, the assessment of aquatic life use support for this stream segment is being moved from impairment Category 5b of Iowa’s Integrated Report to Category 3a (designated use not assessed).