Upper Iowa River IA 01-UIA-239

The Class A1 (primary contact recreation) uses are assessed as "partially supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric mean of indicator bacteria (E. coli) in the 20 samples collected during the recreational seasons of 2012 through 2014 at the Upper Iowa River Watershed monitoring station 17 slightly exceeded the Iowa water quality criterion to protect primary contact recreation uses. Recreation season (March-November) geometric means during the recreation seasons of 2013 and 2014 were above Iowa’s Class A1 water quality criterion of 126 orgs/100 ml. The geometric mean in 2013 was 462 orgs/100 ml, and the geometric mean in 2014 was 616 orgs/100 ml. The geometric mean in 2012, however, was 60 orgs/100 ml and was thus well below the Class A1 criterion. Nine of the 20 samples (45%) exceeded Iowa’s single-sample maximum criterion of 235 orgs/100 ml. According to U.S. EPA guidelines for Section 305(b) reporting and DNR’s assessment/listing methodology, if a recreation season geometric mean is greater than 126 orgs/100 ml., the primary contact recreation uses should be assessed as "impaired" (see pgs 3-33 to 3-35 of U.S. EPA 1997b). Thus, based on the geometric mean from the 2010 recreation season (262 orgs/100 ml), the Class A1 uses remain assessed as “impaired”. Based, however, on the slight violation of the Class A1 criterion in 2012, and based on other and historic geometric means that have met the Class A1 criterion, levels of indicator bacteria in this segment are very low for Iowa streams/rivers, and this impairment should be considered of a very slight magnitude.

The Class B(WW1) uses remain assessed as "not supported" based on information from the 1998-99 statewide survey of freshwater mussels (Arbuckle et al. 2000). The data upon which this assessment is based are now more than 10 years old. Thus, the level of confidence in the assessment is low as water quality conditions may have changed over the 10-plus years since this most recent sampling occurred. Regardless of the age of the data, however, the Class B(WW1) aquatic life uses of this stream segment remain Section 303(d) impaired due to a decline in the freshwater mussel community. Results from this survey suggest a potential impairment to the aquatic life uses of this stream segment. 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’s streams and rivers from the mid-1980s to the late 1990s. Results of this comparison were used by staff of the Iowa DNR to assess the degree to which the aquatic life uses of the sampled stream segments are supported. For purposes of Section 303(d) listing, this assessment was based on the percent change in the number of species of freshwater mussels found in the 1984-85 survey versus the 1998-99 survey. Greater than a 50% decline in species richness from the 1984-85 period to the 1998-99 period suggests an impairment of the aquatic life uses. Species richness of freshwater mussels at the one sample site in this stream segment was 6 in the 1984-85 period and was 0 in the 1998-99 period for a percent change of minus 100%. Based on these results, the aquatic life use are assessed as "not supported" for purposes of both Section 303(d) listing and Section 305(b) reporting. 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 in-stream levels of nutrients (phosphorus and nitrogen). Their study also suggested the importance of stream shading provided by riparian vegetation to mussel species richness. Additional monitoring is needed to better define the biological status of this stream segment as well as the site-specific causes and sources of impairment of these uses that may exist. 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.

Note: Surveys of freshwater mussels were conducted by Iowa DNR staff at one site (Site 48) in this assessment segment in August 2012.

Number of freshwater mussel species from surveys conducted in 1984 (Frest (1987), in 1998 (Arbuckle et al. 2000), and DNR Watershed Improvement Section staff (J. Kurth) in 2012

The results of this monitoring suggest that the decline in the number of species at Site 48 remains, with only one mussel species collected compared to six species in 1984. These result suggest continuing impairment of the Class B(WW1) aquatic life uses.

Contrary to the mussel findings in the late 1990s and in 2012, the fish and other benthic macroinvertebrate communities in this river segment appear to be healthy with results of DNR/SHL biological monitoring in 2006 suggesting “full support” of the aquatic life uses. This evaluated biological assessment was based on data collected in 2006 as part of the DNR/SHL stream REMAP 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 2006 FIBI score was 81 (excellent) and the BMIBI score was 75 (good). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), 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 FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61. This assessment is considered evaluated because the drainage area (584 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria. Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the site used for the assessment doesn't fall in the calibrated watershed size.

Monitoring from 2012 to 2014 at Upper Iowa River Watershed Site 17 near Freeport included analysis for ammonia (two samples), pH (14 samples), and temperature (14 samples). None of the samples collected violated their respective criteria.

The average level of mercury in the 2012 muscle tissue plug samples from three smallmouth bass was 0.179 ppm (standard deviation of 0.036 ppm); this average is well below the advisory threshold of 0.3 ppm. The results of the 2014 sampling showed an average mercury level of 0.247 ppm (standard deviation of 0.134 ppm) in the tissue plugs from three smallmouth bass. The results from the 2016 sampling show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite sample of whole common carp: mercury: 0.06 ppm; total PCBs: <0.06 ppm; and technical chlordane: <0.02 ppm.The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. Because levels of all these contaminants from the 2012, 2014 and 2016 fish tissue monitoring are below Iowa’s advisory trigger levels, the fish consumption uses in this segment of the Upper Iowa River are assessed as “fully supported.”