2016 assessment for West Branch Little Sioux River

West Branch Little Sioux River IA 06-LSR-1983

Silver Lake (Dickinson Co) to headwaters

2016
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 2012 - 2014
Stream/River Water Quality Data	CY 2012 - 2014
Lake Water Quality Data	CY 2010 - 2014
Biological Sampling Data	CY 2010 - 2014*
Fish Kill Data	CY 2010 - 2014
Fish Tissue Sampling Data	CY 2010 - 2014
Continuous Dissolved Oxygen Sampling Data	CY 2010 - 2014
*Biological sites sampled in both 2009 and 2013 were also assessed.

Open Segment Map
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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

9/8/2016 12:54:31 PM by

Updated

9/8/2016 12:54:31 PM by

Use Support

Class A1

Recreation - Primary contact

Not Assessed

Class BWW2

Aquatic Life - Warm Water Type 2

Fully Supported

General Use

General Use water -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 primary contact recreation uses remain not assessed (IR 3a) due to the lack of information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as “fully supported” (IR 2a) based on results of chemical/physical water quality monitoring during 2005. The source of data for this assessment is the results of IDNR/UHL water quality monitoring conducted as part of TMDL development from March through September 2005 at station 11300011. Because these data are now more than five years old, and because as data age beyond five years they are less able to represent current water quality conditions, the assessment type is changed from “monitored” (a higher confidence assessment) to “evaluated” (lower confidence assessment.)

Assessment Explanation

The Class A1 (primary contact recreation) uses remain not assessed due to the lack of data for indicator bacteria (E. coli) upon which to base an assessment. The TMDL monitoring conducted at this station in 2005 did not include monitoring for indicator bacteria.

The Class B(WW2) aquatic life uses are assessed (evaluated) as “fully supported” based on results of IDNR/UHL TMDL-related water quality monitoring conducted in 2005 at station 11300011. Results of this monitoring show no violations of Class B(WW2) water quality criteria for pH or ammonia in the 11 samples collected or for dissolved oxygen in the 10 samples collected from March-September 2005. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), these results suggest “full support” of the Class B(WW2) uses in this river segment.

[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.gov/Portals/idnr/uploads/water/standards/files/swcdoc2.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria. This waterbody has not been assessed for Section 305(b)/303(d) purposes prior to the current (2008) assessment/listing cycle.]

Monitoring and Methods

Assessment Key Dates

3/31/2005

Fixed Monitoring Start Date

9/28/2005

Fixed Monitoring End Date

Methods

220

Non-fixed station physical/chemical monitoring (conventional pollutant only)