Assessment Comments
Assessment is based on results of (1) IDNR/UHL biological sampling in 2002 and 2004 (2) IDNR/UHL ambient monthly water quality monitoring from 2002-2004, and (3) data from the 1998-99 statewide survey of freshwater mussels (Arbuckle et al. 2000).
Basis for Assessment
SUMMARY: The Class B(WW) aquatic life uses are assessed (monitored) as "partially supported" based on 2002 and 2004 IDNR/UHL biological monitoring data and information from the 1998-99 statewide survey of Iowa's freshwater mussels (Arbuckle et al. 2000). Results of ambient water quality monitoring from 2002-04 suggest "full support" of the Class B(WW) aquatic life uses. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this stream segment. The sources of data used for this assessment include (1) results of IDNR/UHL monthly ambient water quality monitoring conducted on Lizard Creek at Highway 169 at Fort Dodge (STORET station 10940001, formerly station 500990) from 2002-2004, (2) results of IDNR/UHL biological (biocriteria) monitoring in 2002, (3) IDNR/UHL biological (REMAP) monitoring in 2004, and (4) information from the 1998-99 statewide survey of Iowa's freshwater mussels (Arbuckle et al. 2000).
EXPLANATION: The Class B(WW) aquatic life uses are assessed (monitored) as "partially supported" based on 2002 and 2004 IDNR/UHL biological monitoring data and results of the 1998-99 statewide survey of freshwater mussels. The 2002 biocriteria FIBI score was 85 (excellent) and the BMIBI score was 57 (good). The 2004 REMAP FIBI score was 70 (good) and the BMIBI scores were 49, 49 (fair). The FIBI average was 77.5 and the BMIBI average was 51.7. The aquatic life use support was assessed as partially supporting (= PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004. The riffle-site FIBI BIC for this ecoregion is 53 and the BMIBI BIC for this ecoregion is 62.
The results of the statewide assessment of freshwater mussels also suggest the potential for an impairment of the aquatic life uses due to a decline in the community of freshwater mussels in this stream segment. This segment of Lizard Creek was sampled as part of the 1998-99 statewide study of freshwater mussels in Iowa streams and rivers (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. 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 Water Quality Bureau to assess the degree to which the aquatic life uses of the sampled stream segments are supported. The results of this sampling on this segment of Lizard Creek, however, do not meet IDNR guidelines for developing a monitored assessment of support for the aquatic life uses that is appropriate to support addition of this waterbody to Iowa's Section 303(d) list. That is, 303(d)-level assessment decisions are developed only for those stream segments having an average of four or more species reported in the 1984-85 (Frest) survey due to the difficulty of interpreting status of mussel communities showing relatively low species richness during the both the historical (1984-85) and current (1998-99) surveys. This information can be used, however, to indicate the potential for an impairment of the aquatic life uses and to indicate the need to conduct additional sampling. Species richness of freshwater mussels at the four sample sites in this segment of Lizard Creek was 0, 1, 2, and 3 in the 1984-85 period and was 0, 1, 0, 0 in the 1998-99 period, respectively, for an average 1984-85 species richness of approximately 2 and a percent change of minus 50%. Based on these results, the aquatic life uses are assessed as “partially supported."
Conversely, results of ambient chemical/physical monitoring suggest very good water quality. None of the 36 samples collected during the 2002-2004 assessment period at Hwy 169 station violated Class B(WW) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen (the minimum dissolved oxygen concentration (7.9 mg/l) is relatively high for ambient monitoring stations and suggests excellent water quality). In addition, no violations occurred in the approximately 30 samples analyzed for toxic metals or in the seven samples analyzed for pesticides and other toxic organic compounds.
Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this stream segment.
