Iowa River IA 02-IOW-624
from confluence with Cedar R. to Johnson-Washington Co. line
- Assessment Cycle
- 2024
- Release Status
- Pending
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 11/1/2023 8:12:55 AM
- Updated
- 12/29/2023 7:43:55 AM
Assessment Summary
The Class A1 use was assessed as “not supported” based on violations of water quality criteria for indicator bacteria. The Class BWW1 use remains assessed as "not supported" based on results of a 1998-99 statewide assessment of freshwater mussels in Iowa streams. The class HH-F use was assessed as "fully supported" based on water quality monitoring data. Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the Class A1 use was changed from 5a (impaired; TMDL needed) to 4a (impaired; TMDL approved). Because not all impairments identified for this segment are covered by the TMDL, this segment remains in Category 5 of Iowa's Integrated Report (impaired; TMDL needed).
Assessment Explanation
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2020-2022 10580002 Iowa
River near Lone Tree
Iowa DNR 6 BIO See Below 940 Iowa
River Lone
Tree Class A1 - Indicator Bacteria: Site ID Data Source ID # Samples per Year (2020/ 2021/2022) 2020 Geometric Mean 2021 Geometric Mean 2022 Geometric Mean Violates Annual Geometric Mean? # 2020 SSM violations / SSM Violations needed for impairment # 2021 SSM violations / SSM Violations needed for impairment # 2022 SSM violations / SSM Violations needed for impairment Violates Annual SSM Significantly >10% Rule? Assessment Type Support Level 10580002 6 8/8/8 79 110 201 YES 2 / 3 2 / 3 3 / 3 YES Mon Not Class A1 – pH: Site ID Data Source ID # Samples / # Years Minimum Value Maximum Value Mean Value # Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 10580002 6 36 / 3 7.9 8.9 8.3 0 7 NO Mon Full Class BWW1 - Binomial Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Mean Value # Violations # Acute / Chronic Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 10580002 6 Chloride 36 / 3 12 54 30 NA 0 / 0 7 NO Mon Full 10580002 6 Dissolved Oxygen 36 / 3 7.4 16.4 11.6 0 NA / NA 7 NO Mon Full 10580002 6 pH 36 / 3 7.9 8.9 8.3 0 NA / NA 7 NO Mon Full 10580002 6 Sulfate 36 / 3 13 47 30 0 NA / NA 7 NO Mon Full 10580002 6 Temperature 36 / 3 0.1 29.2 13 0 NA / NA 7 NO Mon Full Class BWW1 - Toxic Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations >1 Acute / Chronic Violation Assessment Type Support Level 10580002 6 Ammonia 36 / 3 0.33 0.06 0.02 0 / 0 NO Mon Full 10580002 6 Cadmium 20 / 3 0.5 0.5 0.5 0 / 0 NO Mon Full 10580002 6 Chromium 20 / 3 2 0.56 0.5 0 / 0 NO Mon Full 10580002 6 Lead 20 / 3 1 0.91 1 0 / 0 NO Mon Full 10580002 6 Nickel 20 / 3 33 3 2 0 / 0 NO Mon Full 10580002 6 Selenium 18 / 2 2 0.9 1 0 / 0 NO Mon Full 10580002 6 Silver 20 / 3 1 0.902 1 0 / 0 NO Mon Full 10580002 6 Zinc 20 / 3 4.4 1.9 1.4 0 / 0 NO Mon Full
Benthic Macroinvertebrates: Site ID Date Drainage Area (mi2) Ecoregion Major Drainage BM Sample Gear BMIBI score BMIBI Class 47f BMIBI BIT BMIBI Pass/Fail 940 8/30/19 4293 47f MS Floating Art Sub 60 Good 51 Pass Community Assessment Type Assessment Result Support Level IR Category Reason Benthic
Macroinvertebrates Evaluated Pass (1/1) Full Assessment was evaluated
because the drainage area of the sample site Overall Evaluated Pass Full 1 was greater than the
calibrated range. Freshwater
Mussel Survey Avg. # Freshwater Mussel Species Avg. # Freshwater Mussel Species
Increase/Decrease Avg % Freshwater Mussel Species Increase/Decrease Assessment Type Support Level IR Category 1984-85
(Frest 1987) 4 sites 8.75 1998-99
(Arbuckle et al. 2000) 4 sites 0.5 -8.25 -94% Evaluated Not 5b As
presented by Arbuckle et al.(2000), the potential causes of
declines in species richness of Iowa's freshwater mussels include siltation,
destabilization of stream substrate, stream flow instability, and high
instream levels of nutrients (phosphorus and nitrogen). Their study also suggested
the importance of stream shading provided by riparian vegetation to mussel
species richness. Class HH-F - Toxic Parameters:
Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value Number of Non - Detects Mean Value > Criterion or MCL Assessment Type Support Level 10580002 6 Selenium 18 / 2 2 0.9 1 8 NO Mon Full
Class BWW1 - Biological Sampling:
Overall:
Class BWW1 – Freshwater Mussel Sampling:
Assessment Key Dates
1/8/2020 | Monitoring Start |
12/7/2022 | Monitoring End |
8/30/2019 | Biological Monitoring |
3/9/2018 | TMDL Completed |
4/1/1984 | Biological Monitoring |
4/1/1999 | Biological Monitoring |
Methods
120 | Surveys of fish and game biologists/other professionals |
150 | Monitoring data more than 5 years old |
200 | Physical/Chemical Monitoring |
315 | Regional reference site approach |
320 | Benthic macroinvertebrate surveys |
420 | Indicator bacteria monitoring |