The Class A1 (primary contact recreation) uses are assessed (monitored) as "fully supported" based on levels of indicator bacteria that exceeded state water quality criteria. The geometric means of indicator bacteria (E. coli) in the 18 samples collected during the recreational seasons of 2014 through 2016 at Iowa DNR station 10890001 were as follows: the 2014 geometric mean was 27 orgs/100 ml, the 2015 geometric mean was 70 orgs/100 ml, and the 2016 geometric mean was 108 orgs/100 ml. None of the three recreation season geometric means exceeded the Class A1 geometric mean criterion of 126 orgs/100 ml. Three of the combined 18 samples (17%) exceeded Iowa’s Class A1 single-sample maximum criterion of 235 orgs/100 ml.The geometric means of indicator bacteria (E. coli) in the 10 samples collected during the 2014 recreational season at USGS station 05490500 at Keosauqua (the 2014 geometric mean was 50 orgs/100 ml). Two of the combined 10 samples (20%) exceeded Iowa’s Class A1 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 the 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, because none of the recreation seasons geometric means exceeded criteria for Class A1 uses, these uses are assessed as "fully supported."

The Class B(WW1) aquatic life uses remain assessed (monitored) as “partially supported” due to fish kills on July 10, 2006, and on July 7, 2012 on the reach of river between Eldon (Wapello Co.) and Douds (Van Buren Co.). These kills are in a series of kills that have occurred over the last 15 years or so that appear to involve primarily shovelnose sturgeon (Scaphirhynchus platorynchus). Although the cause of the three recent kills and the previous kills remains unknown, the leading hypotheses are (1) that very high water temperatures, very low river flows, and elevated pH levels combine to make ambient levels of ammonia in the river toxic to the ammonia-intolerant shovelnose sturgeon and (2) that the kills are caused by a virus specific to shovelnose sturgeon. The most recent kill in July 2012 was especially severe. According to the local DNR Fisheries biologist, the kill was reported on the lower Des Moines River on July 7, 2012, from approximately Eldon (downriver from Ottumwa) to Farmington in Van Buren County. An estimated 57,000 fish were killed including at least 35,000 shovelnose sturgeon. No specific cause of the kill was identified, but low flow conditions, flow alterations, and very high water temperatures (95+F) are believed to have contributed to the kill.

According to DNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill within the most recent three-year period indicates that the aquatic life uses of a waterbody are only "partially supported.” Thus, the Class B(WW1) aquatic life uses of this river reach were assessed as "partially supported” (303(d) impaired). Also, according to DNR’s assessment methodology, if a cause of a fishkill was not identified during the DNR investigation (cause = "unknown"), or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, typically lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (Category 5 of the Integrated Report). Waterbodies affected by such fish kills at usually placed in IR subcategories 2b or 3b and are added to the state’s list of “waters in need of further investigation”. Due however to (1) the repeated occurrence of these kills over the last 15 years in Wapello and Van Buren counties, (2) the often large numbers of sturgeon killed (thousands), (3) the likelihood that these kills are caused by a pollutant and (4) the possibility that the kills have extended further downstream (possibly to Bonaparte), this impairment was added to Iowa’s 2008 Section 303(d) list (Category 5 of the Integrated Report). This assessment is also applied to upriver segment (IA 04-LDM-1005).

Despite the repeated occurrence of sometimes severe fish kills, resultsof chemical/physical water quality monitoring at Iowa DNR station 10890001, however, suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 27 Ammonia samples (maximum = 0.1 mg/L), 27 Dissolved Oxygen samples (minimum = 7.2 mg/L), 27 pH samples (range = 7.7 to 8.7), 27 Temperature samples (maximum = 27° C), 27 Chloride samples (maximum = 44 mg/L), or 27 Sulfate samples (maximum = 71 mg/L) occurred during monitoring from October 2014 to December 2016. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 10% violations of these conventional parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.

Additionally, results of chemical/physical water quality monitoring at USGS station 05490500 at Keosauqua also suggest “full support” of the aquatic life uses. Monitoring showed no violations of Class B(WW1) water quality criteria for 44 Ammonia samples (maximum = 0.4 mg/L), 41 Dissolved Oxygen samples (minimum = 6.4 mg/L), 44 pH samples (range = 7.3 to 8.9), 44 Temperature samples (maximum = 28° c), 44 Chloride samples (maximum = 83.5 mg/L), or 44 Sulfate samples (maximum = 118 mg/L) occurred during monitoring from January 2014 to December 2016.Class B Toxic (Acute and Chronic) water quality monitoring showed no violations of Class B(WW1) acute water quality criteria for 44 Arsenic samples (maximum = 3.8 ug/L), 2 Dieldrin samples (maximum = 0 ug/L), 44 Selenium samples (maximum = 2.9 ug/L), or 2 p,p'-DDE samples (maximum = 0 ug/L) occurred during monitoring from January 2014 to December 2016. According to U.S. EPA guidelines for Section 305(b) water quality assessments (U.S. EPA 1997b, page 3-17), the EPA guidelines allow up to 1 acute violations of these Toxic parameters before impairment of water quality is indicated. Thus, these results thus suggest “full support” of the Class B(WW1) aquatic life uses.

The (evaluated) assessment of the presumptive Class B(WW1) aquatic life uses was based on data collected in 2016 as part of the DNR/SHL large river stream sampling project. A series of biological metrics that reflect 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 collected in the stream sampling reach. The biological metrics were combined to make a benthic macroinvertebrate index (BMIBI). The index ranks the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2016 BMIBI score was 74 (good). The aquatic life use support was assessed (evaluated) as fully supporting (=FS), based on a comparison of the BMIBI score with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The BMIBI BIC for this ecoregion is 41. Even though this site passed the BMIBI BIC, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because the drainage area above the sampling site (14038 mi2) is much greater than the maximum allowed (500 mi2) for calibrated assessments.

Fish consumption/human-health uses are assessed (monitored) as "fully supported" based on (1) results of EPA/DNR or DNR fish tissue (RAFT) sampling on the Des Moines River NNW of Keosauqua and (2) results of analysis for pesticides and metals in water. This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring. The 2012, 2014 and 2016 whole-fish samples of common carp had generally low levels of the primary contaminants. The 2012 sample contained the following: mercury: 0.111 ppm; total PCBs: 0.24 ppm; and technical chlordane: 0.11 ppm. The 2014 sample contained the following: mercury: 0.04 ppm; total PCBs: <0.39 ppm; and technical chlordane: <0.1 ppm.And the 2016 sample contained the following: mercury: 0.06 ppm; total PCBs: <0.06 ppm; and technical chlordane: 0.12 ppm.With the exception of the level of PCBs in the 2012 sample of whole-fish common carp, all levels of these contaminants are below Iowa’s consumption advisory thresholds. The level of total PCBs in the 2012 sample of whole-fish common carp (0.24 ppm), however, exceeded the 1 meal/week consumption advisory trigger level (0.2 ppm) as defined in Iowa’s fish consumption advisory protocol. According to the DNR/DPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory. Also, according to the DNR/DPH advisory protocol, the previous results for levels of PCBs in whole-fish samples from the Des Moines River do not warrant issuance of an advisory but do indicate the need to conduct additional monitoring to better define contaminant levels in fillet samples from this river segment. Follow-up (fillet) monitoring is needed to better determine (1) levels of PCBs in the edible portions (fillets) of fish in this river segment and (2) whether a consumption advisory for PCBs needs to be issued. The high non-detect level of PCBs in the 2014 whole-fish Common Carp sample (<0.39 ppm) was due to analytical detection levels of 0.13 ppm for each of the three Aroclors (1248, 1254, and 1260) that comprise “total PCBs”.

None of the samples analyzed from 2014 to 2016 by USGS exceeded their respective HH (human health-fish) criteria for arsenic (44 samples), DDE (2 samples), dieldrin (2 samples), and selenium (44 samples).