Moorehead Park Pond IA 06-LSR-1587

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Moorehead Lake are assessed (evaluated) as "partially supported" based on information from the ISU lake survey. Using the median values from these surveys from 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 54, 53, and 58 respectively for Moorehead Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Moorehead Lake in the Eutrophic category. These values suggest low levels of chlorophyll a and suspended algae in the water, very good water transparency, and relatively low levels of phosphorus in the water column. 

The level of inorganic suspended solids was low at Moorehead Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Moorehead Lake (2 mg/L) was ranked 10th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a small population of cyanobacteria exists at Moorehead Lake. These data show that cyanobacteria comprised 38% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (3.4 mg/L) was ranked 7th of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as "partially supported." due to a fish kill in 2007. Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 15 samples(0%), no violations of the criterion for dissolved oxygen in 15 samples(0%), and no violations of the criterion for pH in 15 samples(0%). Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Moorehead Lake. Moorehead Lake Lake was assessed (monitored) as "partially supported" for the 2008 assessment/listing cycle. Based on IDNR’s assessment methodology 2 consecutive assessment/listing cycles without significantly greater than 10% of the samples violating the single-sample maximum criterion are necessary to propose delisting based on pH violations.  There were less than 10% of the samples exceeding the single-sample maximum criterion for both the 2014 and 2016 assessment/listing cycles.   Therefore, the impairment (5a) for pH is suggested for delisting for the 2016 assessment/listing cycle.

Results of a fish kill investigation that occurred on August 16, 2007 also suggest “partial support” of the Class B(LW) uses of Moorehead Lake.   The fish kill was attributed to low oxygen conditions caused by an algae die-off (natural conditions/non-pollutant).   The number and type of fish killed was not reported.   This is the same assessment as that developed for the 2008, 2010, 2012, and 2014 assessment/listing cycle.   The continuance of the IR Category 3b listing is based on IDNR's 2016 assessment methodology that states the following:  the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2014-2014) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”.   If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated” and will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.  

According to the IDNR's Fisheries Bureau, the fish population lake was renovated in 2009.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.