Update of a Pollution Load Screening Model for Functionality within Arc Hydro: Creating ''Smarter'' GIS Data for Water Resources Management

The St. Johns River Water Management District (SJRWMD) has developed an automated GIS tool to update a Pollution Load Screening Model (PLSM) that was developed during the mid-90's to assist in identifying potential problem areas. The PLSM produces annual loads for total nitrogen, phosphorus, suspended solids, biological oxygen demand, lead and zinc for local (stream segment based) drainage areas. Relative differences in loads are identified based on a regional (major basin) scale to identify potential problem areas. The new PLSM / Arc Hydro tool is a significant improvement over current practices because it is contained entirely within the SJRWMD's Arc Hydro data model, resulting in greater flexibility and efficiency, while providing additional model functionality and visualization capabilities. In 2003, the Surface Water Quality Monitoring (SWQM) program at SJRWMD adopted the Arc Hydro data model as a framework for water quality and quantity assessments. The backbone of Arc Hydro is a geometric network representing surface water flow, linked to features representing the landscape (local stream segment-based drainage area, "Catchment" in Arc Hydro) and points of hydrologic interest such as water quality monitoring sites, engineering structures and springs. Among the tools available for use with Arc Hydro is a function to accumulate feature attribute values based on hydrologic connectivity; thus each landscape feature ("Catchment") in the network "knows" its own value for a given field (i.e. annual loads) as well as the accumulated total for that field for its entire upstream drainage area. Implementing the PLSM within the Arc Hydro framework provides a more comprehensive picture of pollutant loading enabling the SJRWMD to better identify potential problem areas for further study. Results to date will be presented, along with ideas for extending the tool's utility.