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Judy A Horwatich

Judy Horwatich is a Hydraulic Engineer with the Upper Midwest Water Science Center.

Over the last 20 years, Judy Horwatich aided local, state, and federal agencies determine the effects that rural and urban runoff has on the environment. Her early career concentrated on agricultural runoff to determine the effectiveness of best management practices on reducing sediment and nutrients to the streams. Her work now focuses measuring the quantity and quality of nonpoint source runoff in urban environments. Judy has assembled 30 years of local, state, and national urban runoff studies and incorporated them into the Source Loading and Management Model (SLAMM). She continues calibrate and verify this model concentrating on Wisconsin parameters. This effort allows Public and private engineers to use WinSLAMM to determine realistic pollution reduction credits for their area of concern. Her recent body of work includes evaluation of several proprietary and non-proprietary stormwater management practices that include hydrodynamic separators, stormwater filters, high-efficiency street cleaners, rain gardens, biofiltration cells and swales, grass swales, and filter strips.  



  • Long-term calibration of Source Loading and Management Model (SLAMM) for the State of Wisconsin
  • Evaluation of proprietary stormwater device that have been installed at various source areas
  • Assessment of filtration and infiltration systems that were designed using the State of Wisconsin Technical standards
  • Utilization of GIS to evaluate the relationship between landuse and water quality

Professional Licenses and Certifications

State of Wisconsin Professional Hydrologist