Twin Springs Creek (aka Spring Falls) IA 01-TRK-181

mouth (S2 T90N R4W Delaware Co.) to spring source in S12 T90N R4W Delaware 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: 3 - Insufficient data exist to determine whether any designated uses are met.
Trend: Unknown
Created: 5/8/2019 8:34:19 AM
Updated: 8/30/2019 6:30:35 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class A2

Presumptive Use

Recreation - Secondary contact

Not Assessed

Class BCW1

Aquatic Life - Cold Water Type 1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

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

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2012

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class B(CW1) coldwater aquatic life uses remain assessed (evaluated) as "partially supported" based on 2007 DNR/SHL biological sampling and on the January 2019 summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau. The Class A1 (primary contact recreation) uses, Class A2 (secondary contact recreation) uses and Class HH (fish consumption) uses remain "not assessed" due to the lack of information upon which to base an assessment.

Assessment Explanation

The assessment of the Class B(CW1) aquatic life uses was based on data collected in 2007 as part of the DNR/SHL coldwater stream sampling project. A series of biological metrics which reflect coldwater 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 that were collected in the stream sampling reach. The biological metrics were combined to make a coldwater benthic index (CBI). The index ranks the biological integrity of a coldwater stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2007 CBI score was 43.The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the CBI score with biological impairment criteria (BIC) established for the 2012 Section 305(b) report.The biological impairment criteria were determined from a statistical analysis of data collected at coldwater stream reference sites from 1994-2011.The CW BIC is 60 and this segment passed the CW BIC 0/1 times in 2007.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years in a five-year period to be considered “monitored”. This segment had a single sample collected in 2007. Additionally, these data are now greater than five years old. 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 contrast to the benthic macroinvertebrate sampling, the updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in January 2019, suggests the Class B(CW1) uses be assessed as "fully supported". According to the updated summary, Twin Springs Creek (aka Spring Falls) is in the group of Iowa coldwater streams that supports natural reproduction of trout. Based on results of surveys by the DNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit fairly consistent natural reproduction and maintain a viable population of Brown Trout without any stocking (a Category I stream).

Monitoring and Methods

Assessment Key Dates

1/1/2019

Biological Monitoring

9/17/2007

Biological Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

150

Monitoring data more than 5 years old

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

380

Quantitative physical habitat assessment