During 1992 the Thirty Lakes Watershed District began testing precipitation events for Atrazine.  This initial Atrazine study was sparked by a paper given at the National Monitoring and Evaluation Conference and Nonpoint Source Workshop held in Chicago on March 10-12, 1992.  At the conference Mr. Donald Goolsby (USGS) gave a paper on the atmospheric deposition work he had conducted in the Mississippi River Valley, Lake Superior and sites in eastern Wisconsin.  Upon receiving the findings from the initial Atrazine study, the District Managers decided to extend the study to include Total Phosphorus and in some instances Total Suspended Solids.  The atmospheric sampling revealed precipitation events that provided phosphorus concentrations that were two orders of magnitude greater than phosphorus concentrations observed in the District’s Lakes.  Sampling and monitoring continued, by the Lake Hubert Conservation Association, in 2000 through 2003.  In 2004, atmospheric tracking of the storm events was added to the current study based on the recommendation of Cyril Durrenberger.  Cyril Durrenburger is a summer resident on Round Lake and has been a valuable resource in guiding the District in their atmospheric testing projects.  Cyril is currently a senior lecturer in Chemical Engineering and a Research Fellow at the Center for Energy and Environmental Resources at the University of Texas at Austin.  His research interests lie in issues related to air quality with a focus on atmospheric modeling and emissions inventory development.  He spent 28 years with the Texas Natural Resource Conservation Commission and Texas Air Control Board prior to joining the University of Texas.  He has authored over 18 technical papers and has assisted the EPA in developing the guidance for the new 8-hour ozone standard and fine particulate standards.

Atmospheric tracking of the storm events was accomplished by using NOAA’s (National Oceanic Atmospheric Administration) Air Resources Laboratory modeling software called HYSPLIT.  The Air Resources Laboratory specializes in research relating to air quality and climate. HYSPLIT is a Hybrid Single-Particle Lagrangian Integrated Trajectory model that computes simple air parcel trajectories along with complex dispersion and deposition simulations.  The HYSPLIT model generates a map based either on a forward or backward trajectory of an air mass for a specified duration.  Based on the information entered into the model, a specific air mass/storm event can be tracked.  The purpose of the storm event tracking was to determine where the increase in phosphorus deposition delivered in a rain event is coming from.

Results from the first HYSPLIT graphs indicated a possible trend in the storm events and phosphorus deposition.  With this information in hand, Thirty Lakes Watershed District Managers encouraged other Watershed Districts to participate in an extended precipitation study.  Two Districts in ideal locations decided to participate in the statewide study, the Red Lake Watershed District and the Shell Rock Watershed District. With Red Lake representing the Northern portion of Minnesota, Shell Rock located in Southern Minnesota, and Thirty Lakes Watershed District located in the Central part of the state, the study areas were set.