Historically, monitoring on Fourmile Creek was done through the IOWATER program, a voluntary water monitoring program supported with expertise and resources through the IDNR and local partners, and results were obtained from Mary Skopec, IOWATER Program Coordinator and Research Geologist. Field measurements were taken for nitrate, nitrite, phosphorous, chloride, dissolved oxygen, and water transparency. Laboratory tests were also run for nitrate, nitrite, orthophosphate as P, total phosphate as P, turbidity, E. coli bacteria, bromide, fluoride, ammonia nitrogen as N, sulfate, and total coliform
bacteria. There are 10 monitoring sites along Fourmile Creek and each was sampled one to
two times per year from 2004 to 2009 and monthly starting in 2010.


The general findings of the analyzed data are as follows:

  • phosphorous levels are high throughout the watershed, with lab data suggesting
    phosphorous is coming from wastewater discharges
  • dissolved oxygen levels are generally normal
  • transparency/water clarity measurements vary with season, but are typically high
  • nitrate concentrations are typically normal to high
  • chloride concentrations increase from upstream to downstream, due to larger road
    salt applications in the more urban areas downstream, but are typically low
  • E. coli bacteria levels are high throughout the watershed
  • turbidity measurements are low throughout the watershed

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Pollutant Sources

Based on the monitoring results, the pollutants of concern in the watershed were
prioritized by stakeholders and the WMA. These include groups of both primary and
secondary pollutants. Primary pollutants include sediment and bacteria and secondary
pollutants include phosphorous and nitrogen. Although the Rapid Assessment of Stream
Conditions Along Length (RASCAL) and Revised Universal Soil Loss Equation (RUSLE)
assessments provided ample information on a watershed level, monitoring data can provide targeted information on a local level for priority areas to implement water quality projects. Currently, there is inadequate monitoring data available for the needs of this plan. This proves difficult to determine the origin of the pollutants and quantities present. More robust monitoring of these parameters is addressed in a later
section.


Priority Pollutants

Sediment loading and bacteria levels were prioritized as the primary pollutants in the
Fourmile Creek Watershed because of the recreational contact concerns. Even though
Fourmile Creek is not a drinking water source, there is still a pollutant concern due to
human contact with the water.


Sources of sediment loading could be from any combination of streambank erosion and
stormwater runoff from the surrounding rural and urban land uses. Excess amounts of
sediment can cloud the stream and harm underwater organisms.


Sources of bacteria could be from any combination of pet waste, wildlife, agriculture,
Leaking, or overflowing septic systems and failing infrastructure. Bacteria levels can
fluctuate greatly based on storm runoff, leaking sewage lines, the time of day, and the time of year. Elevated nutrients and water temperatures also influence bacteria levels, causing health risks to anyone encountering the water.


Secondary Pollutants

Phosphorous and nitrogen were set as secondary constituents of concern in the Fourmile
Creek Watershed, since Fourmile Creek is not a drinking water source but high levels of
these pollutants have a negative impact on the stream. These nutrients are essential for
plant and animal growth and naturally abundant in the environment. Elevated nutrient
levels can cause overstimulation of growth of plants and algae. Overgrowth can cause
decrease dissolved oxygen in a stream, block light to deeper water, and clog water intakes. Both constituents are being considered for further monitoring and mitigation, if and when funding would be available.


For Historic Monitoring Report, Click Here!

Fourmile Creek and its tributaries run for over 40 miles before entering the Des Moines River