REFINING THE INDIAN RIVER LAGOON (IRL) TOTAL MAXIMUM DAILY LOADS (TMDL)
The TMDL Development for the Indian River Lagoon relied heavily on the use of spatial data to estimate past and current (as of year 2000) runoff and pollution loadings. The Pollution Load Screening Model (PLSM) is a GIS-based model that combines several spatial input layers: land use land cover, soils, treatment, and annual rainfall.
Phase I redefined all the input layers for recent historic years (2000 and 2004), and rebuilt the PLSM model using project specific runoff coefficients, concentrations, and delivery ratios. Monthly draft watershed direct runoff volume, TN and TP loadings were provided for 192 months (January 1995 to December 2010) which are currently being evaluated by other project team members for calibration with other modeling results and/or evaluation of other water quality parameters and potentially seagrass abundance or extent.
Phase II is currently in progress and will refine input layers based on stakeholder review, refinement of treatment type efficiencies, and the incorporation of base flow in the watershed model. Phase II also includes calibration of the watershed model, report and model documentation tasks, and the final allocation of baseline loadings (year to be established) among stakeholders.