Willow Creek IA 02-WIN-848

mouth (SW 1/4 S32 T98N R21W Worth Co.) to headwaters (Worth Co.)

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

Open Segment Map
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Cycle: 2018
Release Status: Final
Overall IR: 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trend: Unknown
Created: 5/2/2019 8:56:28 AM
Updated: 8/2/2019 9:27:16 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

Fully Supported

General Use

General Use water -

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 presumptive Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported" based on results of DNR/SHL biological sampling in 2010, 2013 and 2016.

Assessment Explanation

The presumptive Class B(WW1) aquatic life uses are assessed (evaluated) as “fully supporting” based on data collected in 2010, 2013 and 2016 as part of the DNR/SHL stream biocriteria project. The 2010 FIBI score was 53 (good) and the BMIBI score was 73 (good). The 2013 FIBI score was 54 (good) and the BMIBI score was 68 (good). The 2016 FIBI score was 60 (good) and the BMIBI score was 48 (fair). A series of biological metrics that reflect stream water quality and habitat integrity were calculated from the biocriteria 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 aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The riffle habitat FIBI BIC for this ecoregion is 53 and the BMIBI BIC for this ecoregion is 62. Even though this segment passed the FIBI BIC 3/3 times and passed the BMIBI BIC 2/3 times in the last seven years, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it is a small headwater stream and doesn’t fall in the calibrated watershed size.

This assessment is considered “evaluated” (of lower confidence) due to the lack of a biological assessment protocol for headwater streams. Prior to the changes in Iowa’s surface water classification that were approved by U.S.EPA in February 2008, this stream was classified only for general uses.

Monitoring and Methods

Assessment Key Dates

9/28/2010

Biological Monitoring

9/29/2013

Biological Monitoring

8/10/2016

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