Iowa DNR
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Water Quality Assessments

Impaired Waters List

Buffalo Creek IA 01-WPS-378

from confluence with unnamed tributary in N 1/2 S27T88NR7W (Buchanan Co.) to confluence of the East Branch and West Branch of Buffalo Creek in S35 T90N R8W Buchanan Co.

Assessment Cycle
2008
Result Period
2004 - 2006
Designations
Class A1 Class B(WW-2)
Assessment Methodology
Assessment Type
Evaluated
Integrated Report
Category 5b
Legacy ADBCode
IA 01-WPS-0130_2
Overall Use Support
Not supporting
Aquatic Life Use Support
Not supporting
Primary Contact Recreation
Not assessed
Documentation
Assessment Comments

Assessment remains based on results of the statewide assessment of freshwater mussels in Iowa (Arbuckle et al. 2000). Potential causes & sources of impairment were applied to all sites in study.

Basis for Assessment

[Note:  Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses.   Due to changes in Iowa’s surface water classification that were approved by U.S.  EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses.   The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses).   Thus, for the current (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.   The Class B(WW2) aquatic life uses remain assessed (evaluated) as "not supported" based on information from the report "Statewide Assessment of Freshwater Mussels (Bivalva, Unionidae) in Iowa Streams" by Arbuckle et al.  (2000).   As part of this study, sampling results from 1998 and 1999 (Arbuckle et al.  2000) were compared to results from stream sites surveyed in 1984 and 1985 by Frest (1987).   On a statewide basis, this comparison showed sharp declines in the numbers of mussel species ("species richness") in Iowa streams and rivers from the mid-1980s to the late 1990s.  

EXPLANATION:  For purposes of Section 303(d) listing, the assessment of the Class B(WW2) aquatic life uses remains based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey.   For stream segments having four or more species reported for the 1984-95 survey, results of this comparison were used by staff of the Iowa DNR TMDL & Water Quality Assessment Section to assess the degree to which the aquatic life uses of the sampled stream segments are supported.   Greater than a 50% decline in species richness from the 1984-85 to the 1998-99 period suggests an impairment of the aquatic life uses.   Species richness of freshwater mussels at the three sample sites in this segment of Buffalo Creek  was 4, 6, and 5, respectively, in the 1984-85 period (average of approximately 7 species) and was 0, 2, and 0, respectively, in the 1998-99 period (average of less than one  species) for an average percent change of minus 89%.   Based on these results, the aquatic life uses are assessed (monitored) as “not supported.”  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.   Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).   Despite this change in assessment type, this waterbody remains in IR Category 5b.

Monitoring and Methods
Assessment Key Dates
9/30/1999 Biological Monitoring
9/30/1985 Biological Monitoring
Methods
120 Surveys of fish and game biologists/other professionals
320 Benthic macroinvertebrate surveys
Monitoring Levels
Biological 3
Habitat 0
Physical Chemistry 0
Toxic 0
Pathogen Indicators 0
Other Health Indicators 0
Other Aquatic Life Indicators 0
# of Bio Sites 3
BioIntegrity Poor
Causes and Sources of Impairment
Causes Use Support Cause Magnitude Sources Source Magnitude
Nutrients Aquatic Life Support Moderate
  • Bank or Shoreline Modification/Destabilization
  • Removal of Riparian Vegetation
  • Moderate
  • Moderate
Siltation Aquatic Life Support Moderate
  • Bank or Shoreline Modification/Destabilization
  • Flow Regulation/Modification
  • Removal of Riparian Vegetation
  • Moderate
  • Moderate
  • Moderate
Other habitat alterations Aquatic Life Support Moderate
  • Bank or Shoreline Modification/Destabilization
  • Flow Regulation/Modification
  • Removal of Riparian Vegetation
  • Moderate
  • Moderate
  • Moderate