Modeling Phosphorus Transport in Grass Buffer Strips

An event-based computer model, GRAPH, was developed to simulate phosphorus (P) transport in grass buffer strips (GBS) by incorporating submodels into SEDIMOT II, a stormwater and sediment transport model developed for strip mine reclamation. GRAPH considers the effects of advection processes, infiltration, biological uptake, P desorption from the land surface to runoff, adsorption of dissolved P to suspended solids in runoff, and the effects of changes in sediment size distribution on P transport. Required input data include: rainfall intensity and duration, an inflow hydrograph, a sediment graph, sediment size distribution, GBS dimensions and hydraulic characteristics, inflow graphs for dissolved P, P desorption and adsorption reaction coefficients for soil and plant matter, and the P content of each soil particle size class. GRAPH simulates time varying infiltration, runoff discharge, sediment yield, particle size distribution, and dissolved and sedimentbound P discharge along with sediment and P trapping efficiencies in GBS. GRAPH was verified using data from experimental field plots. Model predictions and observed P transport in the GBS compared favorably.