MOVEMENT OF NITROGEN THROUGH AN AGRICULTURAL RIPARIAN ZONE .2. DISTRIBUTED MODELING

The Nutrient Transport and Transformation model (NTT) is a generalized fate, speciation and transport model capable of simulating the moveme nt of nutrients in the environment. The hydrologic model is an energy- driven, distributed parameter model that couples surface and ground wa ters. The vertical discretization consists of overland flow, perched s aturated layer, root zone, percolation zone, and groundwater. The chem ical model is based on the mass balances of nitrate, ammonium ion, org anic nitrogen, humus material, organic phosphorus, phosphate, litter a nd biomass in the unsaturated zone and the groundwater. Geochemical pr ocesses affecting the nitrogen species mass balance that are included are nitrification, denitrification, plant uptake, mineralization, litt er partition, humidification, decomposition and biomass growth (uptake ) and respiration. The NTT model was used to simulate the fate, transp ort and speciation of nitrogen through a corn riparian zone using data collected during the summer months of 1992. The NTT model was shown t o be capable of simulating the hydrologic and biogeochemical processes occurring in riparian zones. The root mean square error between the s imulated and observed nitrate concentration is 1 mg/l. The model can b e used in the design of riparian buffers for nonpoint source pollution control.