Improved Daily Nitrate and Ammonium Concentration Models for the Chesapeake Bay Watershed

Abstract : A revised model of daily ammonium and nitrate wet-fall concentration and wet deposition was developed for use in the Phase 5 Chesapeake Bay Watershed Modeling Program. The preceding model (Valigura et al, 1996) was based on precipitation chemistry data from 1984 through 1992. The revised model was derived data from 1984 through 2001 and was extended to include parameters of precipitation event history, land cover composition, and long-term concentration trends, as well as, a refined quantification of seasonal variation. Ammonia and nitrous oxide emission levels were also evaluated for use as predictors of daily wet-fall concentration. Improvements in model accuracy for the expanded study period were achieved. The revised model was implemented to provide direct estimates of daily wet-fall concentration and wet deposition to the land and river modeling segments of the CBW Modeling Program, as well as, for the geographic region surrounding the CBW.