Development of integrated hydro-biogeochemical model in a forest catchment

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An integrated hydrochemical model for description and forecast of biogeochemical responses in a forest catchment has been developed based on intensive observation in a temperate forest catchment. As the prototype of the basin-scale hydrochemical modeling taking the saturated-unsaturated infiltrated into the soil chemical process, a numerical model for SiO_2 concentration generation was proposed. The process oriented 1-D pH simulation model and nitrogen/carbon dynamics model were also proposed. The basin-scale model has multiple subunits with each soil depth that is determined by actual soil depth distribution. A coupling calculation of saturated-unsaturated infiltration and convection-diffusion process is conducted for each subunit using observed rainfall quantity and quality data set. Using the properly estimated chemical weathering rate, the model can reproduce the observed timesequential change of the SiO_2 concentration of stream and subsurface groundwater for the duration of both storm event and base flow periods. The 1-D pH simulation model is based on the observed information of buffering systems in actual soil layr. The model simulates the CO_2 gas profile and alkalinity of soil solution. It can successfully reproduce the seasonal changes in pH of groundwater and streamwater.