Integration of a benthic sediment diagenesis module into the two dimensional hydrodynamic and water quality model – CE-QUAL-W2

Current CE-QUAL-W2 mainly simulates hydrodynamics and eutrophication processes in the water column. The benthic sediment processes and sediment–water interactions have been neglected or very much simplified using zero-order and first-order rates. In this study a benthic sediment diagenesis module was developed and integrated into CE-QUAL-W2. Enhanced CE-QUAL-W2 was capable of simulating the dynamic releases of ammonium, nitrate, phosphorus, dissolved silica and dissolved methane from the sediment to the overlying water, as well as benthic sediment oxygen demand. The oxidation of sulfides is included for salt water sediments. The ability of CE-QUAL-W2 model to correctly predict sediment–water nutrient fluxes and sediment oxygen demand was evaluated against SedFlux and CE-QUAL-ICM models through a series of case studies. These case studies were chosen for representing various sedimentation and environmental conditions. The simulated sediment–water nutrient fluxes and sediment oxygen demand over time were generally in good agreement with these two model results for all data sets. The effect of benthic sediment diffusive thickness, particle mixing coefficients on nutrient releases from sediments and sediment oxygen demand were examined. Enhanced CE-QUAL-W2 model was also applied to the Lower Minnesota River for further evaluating its performance. This paper presents the sediment diagenesis module development, validation tests and application of the enhanced CE-QUAL-W2 model.