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A procedure was developed for statewide NPS pollution assessment in Virginia on a watershed basis using the GWLF model. The model was calibrated to output from the Chesapeake Bay Programs Chesapeake Bay Watershed Model (CBWM) for an area covering approximately half of the state to provide consistency with watershed priorities identified through CBWM modeling. Statewide regions were defined based on common watershed attributes, so that calibration adjustments made within the Bay drainage area of these regions would have a basis for application to uncalibrated areas of the state. Regional calibration adjustment factors were calculated for various parameters and then applied to a new set of GWLF parameter values that were re-evaluated for the statewide NPS assessment model runs using watershed-specific rainfall, landuse, and other data.