Ecological impacts of agricultural runoff to Midwestern lakes
Agricultural activities strongly impact water quality in lakes. Enriched Phosphorus (P) discharged from agricultural areas can cause excess growth of phytoplankton and subsequent hypoxia in lakes. Large amounts of phosphorus can be transported during storm events from inflows to lakes. However, the P loadings in relation to the severity of the storm event have not yet been quantified. The objective of this study was to estimate how much agircutural areas in the Midwest contribute to lake eutrophication during severe storm events, as well as regular conditions (baseflow condtions). We expect to see more phosphorus transported with stormwater and baseflow in hyper-eutrophic lakes. To understand the impact these events on external P loading and lake water quality, we sampled baseflow and stormwater over a six month period at Yankee Hill, a hyper-eutrophic lake and Wagon Train, a eutrophic lake in Nebraska. Stormwater was collected by in field water samplers that sampled over a three-day period in three-hour increments and USGS Stream gauges were used to collect precipitation data.
Preliminary results show that Yankee Hill has higher external P loading than Wagon Train. During storm events, Yankee Hill inflows introduced larger amounts of P into the lake. Wagon Train was impacted by agricultural runoff to a lesser degree and had lower concentrations of P brought into the lake. We suggest that quantifying the impact agricultural runoff has on lake eutrophication will better inform watershed management decisions and farmer’s best management practices.