Iowa DNR
ADBNet

Water Quality Assessments

Impaired Waters List

Crooked Creek IA 03-SKU-918

mo to confl of E Fk & W Fk Crooked Crs

Assessment Cycle
2018
Release Status
Final
Data Collection Period
Overall IR Category
2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trend
Unknown
Created
5/14/2019 10:30:05 AM
Updated
5/14/2019 10:30:56 AM
Assessment conducted in accordance with Iowa's 2018 IR methodology
Use Support
Class A1
Not Assessed
Class BWW2
Fully Supported
General Use
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (evaluated) as “fully supported” based on data collected in 2005 as part of the DNR/SHL stream REMAP project.

Assessment Explanation

This evaluated biological assessment was based on data collected in 2005 as part of the DNR/SHL stream REMAP sampling project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2005 FIBI score was 39 (fair) and the BMIBI score was 59 (good). The aquatic life use support was assessed as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The FIBI BIC for this ecoregion is 36 and the BMIBI BIC for this ecoregion is 51. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. This segment passed both the FIBI and BMIBI BICs in 2005.

This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years over a five-year period. Additionally, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). However, despite this change in assessment methodology and type, this waterbody remains in IR 2a.

Monitoring and Methods
Assessment Key Dates
7/14/2005 Biological Monitoring
Methods
150 Monitoring data more than 5 years old
315 Regional reference site approach
320 Benthic macroinvertebrate surveys
330 Fish surveys
380 Quantitative physical habitat assessment