Modeling Extreme Hydrologic and Pollutant Loadings to a Riparian Wetland.

Extreme climatic events for wetlands can include large rainfall events that have the potential to short-circuit the water retention and nutrient and pesticide removal and retention functions of the wetlands.  This is especially critical in treatment wetlands placed in landscapes where there is little or no management control on the amount of water entering the wetland.  These extreme events will often lead to reduced treatment efficiency for the event and because of a high proportion of pollutant load moving in the extreme events, they will probably limit the overall treatment efficiency.  We will use the Riparian Ecosystem Management Model (REMM) to examine multiple extreme events entering a riparian buffer.  Previous modeling studies found that higher loadings lead to less per cent retention of N and P up to about a 30 m buffer but that a 30 m buffer was equally effective for both high and normal loading scenarios.  Building on the earlier modeling and field studies, we will determine how extreme hydrologic events may differ from extreme nutrient, pesticide, and sediment transport events.  The simulation scenarios are based on a well-studied riparian treatment wetland established to buffer a farm pond from a year-round forage production system using liquid animal manure applications to provide water, N, and P.  Results will be discussed relative to the effects of extreme events on both input/output budgets and effects on internal nutrient cycling rates and pesticide retention processes.