The hydraulic properties of peat are well known to be different depending on the depth from the ground surface. Conventionally, the groundwater movement in a fixed point on peatland has been analyzed by the method of Tank Model, for instance, and has attained fairy good results. However, when we need to apply this method to the extensive area, there are issues of solving a vast number of parameters to be determined at each point. Using the motion equitation based on the Darcy's law and the continuity equation is another conventional solution for calculating the groundwater flow in extensive area, but the properties of peat is scarcely reflected to this model. In this study, first we formulated the hydraulic properties of peat such as porosity and permeability from the observed fluctuations of groundwater table and amount of rainfall. Then we carried two-dimensional flow model for unconfined groundwater in two methods. One is conventional method based on Darcy's law, and the other is proposed method considering hydraulic properties of peat. By using newly defined T-parameter, which has homogeneous element with the coefficient of transmissivity, the peat hydraulic properties have been represented as the factor of depth, and this derived good result in simulation of groundwater fluctuations in the latter method.
