Modeling water balance components in relation to field layout in lowland paddy fields .1. Model development

In this study, a water balance model applicable to lowland paddy fields was developed. The model inputs consist of irrigation supply, climatic data, soil parameters and layout dimensions. The model is formulated to simulate various processes such as evapotranspiration, seepage and percolation, and surface runoff as they occur in the field water balance system. The model is able to predict the changes in water balance components under different land management and hydrological conditions. The model can be applied either for plot-to-plot or independent plot layouts. It was validated using data collected from controlled plot experiments. The details of model development and validation are outlined in this paper.