Drainage Ditch 71 IA 03-SSK-963

mouth (SE1/4 S11 T86N R24W Hamilton Co.) to confluence of Rahto Brach Ditch and Loop Branch Ditch in SE1/4 SE 1/4 S18 T87N R24W Hamilton 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
View assessment methodology in new window

Cycle: 2018
Release Status: Final
Overall IR: 3 - Insufficient data exist to determine whether any designated uses are met.
Trend: Unknown
Created: 5/14/2019 1:12:18 PM
Updated: 5/14/2019 1:13:14 PM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low fish & invert IBIs- cause unknown

Support Level

Further Investigation Needed

Impairment Code

3b-c - Use potentially biologically impaired based on calibrated IBI metrics.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2004

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

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 remain assessed (evaluated) as "partially supported" based on results of DNR/SHL biological sampling in 1997.

Assessment Explanation

The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as “partially supporting” based on data collected in 1997 as part of the DNR/SHL stream biological sampling project. 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 2003 FIBI score was 20 (poor) and the BMIBI score was 41 (fair). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), 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 non-riffle FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This segment failed both the FIBI and BMIBI BICs in 1997.

This assessment is considered "evaluated" because there were not two or more samples collected in multiple years from 2010-2014. According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).

In addition, the data upon which this biological assessment is based are now more than ten years old. As water quality data age, they are less able to represent current water quality conditions. As data age beyond ten years, their ability to represent current water quality conditions is increasingly suspect. Despite the age of these data, the aquatic life uses of this assessment segment will remain “partially supporting/evaluated” and will remain on Iowa’s list of waters in need of further investigation (IR Category 3b-c). Additional monitoring is needed in this assessment segment to update status of its aquatic communities.

Monitoring and Methods

Assessment Key Dates

10/9/1997

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