Modeling of Watershed Scale Mass Circulation Structure on Nitrogen and Carbon

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This study was aimed to establish an integrated nitrogen-carbon mass circulation model for watershed scale. Since solute movement in a watershed is governed largely by hydrological runoff processes, the mass circulation model was developed based on a watershed water quality model combining hydrological runoff and water quality processes. The DNDC model was employed for modeling the dynamic processes of biological metabolism. The study was conducted for the Cidanau watershed in the western part of Java Island, Indonesia. The main results of the study are summarized as follows: (1) Development of watershed runoff model and watershed water quality model Sugawara's Tank Model was applied on sub-catchment basis for the hydrological runoff processes. A watershed water quality model was developed by adding water quality processes to the Tank Model. The model's outputs on effluent load discharges at each sub-catchment's outlet were utilized for the following analysis. (2) Analysis on nitrogen … More balance in the watershed. The watershed was divided into 6 blocks based on tributaries alignment and topography. Considering several categories of land use such as paddy fields, upland fields, garden forest, residential area and so on, nitrogen flow in each land use type was analyzed. The nitrogen balance model for the whole watershed was established by combination of these land use wise nitrogen flow models. (3) Modeling of nitrogen-carbon mass circulation structure in the watershed. The DNDC (DeNitrification and DeComposition) model was employed for metabolic behaviors of nitrogen and carbon. The DNDC was applied in the same manner as the above nitrogen balance model Namely, the watershed scale mass circulation model on Nitrogen and carbon was developed by replacing the above nitrogen flow model for each land use type by the DNDC model. The model could perform properly and its outputs on mass balance factors were considered reasonable. Thus, the result of models development was satisfactory. Utilization of these models is expected to contribute for materializing batter watershed management. Less