—Sandra Fox, St. Johns River Water Management District
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Demand for water in central Florida may soon exceed available groundwater sources, necessitating consideration of alternative sources for water supplies. Among these are surface waters from the St. Johns River. Multiple working groups at the St. Johns River Water Management District (SJRWMD) are addressing the potential effects of these withdrawals on a diverse set of environmental resources. The wetlands working group is assessing the potential effects of reduced stage and flow on a disparate set of wetlands using a GIS modeling approach in ArcMap. To restrict the domain of the model, a boundary was created using elevation data (both raster and vector), beyond which effects were not expected. In addition, to facilitate analyses, the river was segmented into nine regions based upon existing divisions (SJRWMD Major Basins), geomorphology and water resources character such as tidal influence, local springs, river shape, soils, and wetland types. Using a custom ArcMap spatial data summary tool, each of the nine river segments was summarized for soil characteristics, wetland community and drainage area land use in order to first describe the resource. The diversity along the river's 475-plus kilometers is considerable, suggesting that this regionalized approach will help by focusing the analysis on manageable units. The GIS model identifies wetlands that are susceptible to changes in stage, flow or water quality by using a “decision square approach” incorporating soils, wetlands and hydrological characteristics. Additionally, because wetland/water body edge is important habitat to many species, the wetland community at the river edge was measured using a SJRWMD wetlands dataset. Model results to date will be presented.