CHANGES IN SURFACE WATER QUALITY IN THE STORM LAKE WATERSHED

Clean water is needed for healthy ecosystems and recreational activities, but managing water for these purposes can be difficult. To address long-standing flooding and water quality issues, the City of Storm Lake is investing in infrastructure to clean and better manage surface water around the city in the Storm Lake watershed. Examples of projects include the construction of Abner Bell wetland, improved water control structures for Little Storm Lake, updates to storm sewers, instillation of bioreactors, and the dredging of Storm Lake. There is though a need to assess these projects in order to determine if the City of Storm Lake’s efforts are improving water quality. The purpose of this study was to assess the water quality in order to determine anion and cation concentrations, dissolved oxygen concentrations, and turbidity values. Data for this summer research project were collected from May-July at area creeks, Storm Lake, Little Storm Lake and from bioreactors.

The data indicate that sediment amounts, measured as turbidity, decreased as water flowed through the Storm Lake watershed. Nitrate as nitrogen, NO₃^-- N, concentrations were the greatest at West Creek and Powell Creek, 12.0 and 8.2 mg L^-1, respectively. The NO₃^--N concentrations dissipated quickly to less than 1 mg L^-1 upon entering Storm Lake, indicated by a boat deployed Nitratax sensor. The airport bioreactor lowered NO₃^--N concentrations from 8.5 mg L^-1 to 0.4 mg L^-1. The elevated NO₃^--N values are hypothesized to be from agricultural tile drain water. Elevated chloride, Cl^-, concentrations were common at the urban locations Abner Bell and the Field of Dreams bioreactor. These locations, which collect urban and rural waters, had average Cl- concentrations of 84.1 mg L^-1 and 100.4 mg L^-1, respectively. These data will be used to help long-term planning for the City of Storm Lake and will be compared to previously collected data to determine if initial projects are having an impact on water quality.