Aquatic Nutrient Simulation Modules (NSMs) developed for hydrologic and hydraulic models
Abstract This report offers details regarding the theory and mathematical formulations used within the newly developed nutrient simulation modules (NSMs) and its supporting water quality modules. The NSMs model the aquatic ecosystem by computing the changing concentrations of water quality constituents in a unit volume of water. The NSMs includes two kinetics: NSMI, NSMII. The levels of NSMs are determined by the number of interacting state variables involved in water quality simulation and the degree of their interactions. NSMI models algae and benthic algae biomass, simple nitrogen and phosphorus cycles, organic carbon, carbonaceous biochemical oxygen demand, dissolved oxygen and pathogen using 16 state variables. Water quality state variables may be individually activated or deactivated. Using 24 state variables, NSMII models multiple algal groups, benthic algae, nitrogen, phosphorus, and carbon cycles, carbonaceous biochemical oxygen demand, dissolved oxygen, and pathogen. Additionally, an optional benthic sediment diagenesis module was developed for coupling with NSMIIs water column kinetics. Sedimentwater fluxes of dissolved oxygen and nutrients are internally computed in the sediment diagenesis module. The NSMs and its supporting water quality modules are written in Fortran for Windows and are packaged as plug in dynamic linked libraries. Each module must be coupled with hydrologic or hydraulic models to perform water quality analysis.