Model development for nutrient loading from paddy rice fields

The objective of this study was to develop a model groundwater loading effects of agricultural management systems in paddy fields (GLEAMS-PADDY) to predict nutrient loading to surface waters from paddy rice fields. This model was developed by modifying the GLEAMS model that is used for uplands. The GLEAMS-PADDY model is composed of hydrology and chemical sub-models. In the hydrology sub-model of the GLEAMS-PADDY model, the ponded depth routing method was used to handle ponded water condition of paddy fields. With the chemical sub-model, the soil was assumed to be saturated, and the soil profile in the root zone was divided into oxidized and reduced zones.