Permalink : http://hdl.handle.net/2115/49060

JaLCDOI : 10.14943/gbhu.75.73

Large heterogeneity in an alluvial fan influences considerably on groundwater flow field. Applied to groundwater simulation, however, an alluvial aquifer, consisted of permeable gravelly sediments, is often simplified as a single or a few homogeneous layer(s) due to its complexity, lack of hydrogeological information, and knowledge. In a previous study in the Toyohira alluvial fan, we have formulated a relationship between hydraulic conductivities and auxiliary variables in undisturbed gravelly cores by focusing on the effective grain size diameter and lengths of matrix packing level. In this study, a permeability distribution model with the one-meter resolution was yielded by estimating spatial probabilities of auxiliary variables, and then was applied to groundwater flow and heat transport coupling simulation. The simulation results showed preferential flow vectors in high permeable cells, resulting in complex contours of heads and temperatures. It was inferred that such complicated groundwater flow fields occurred in actuality in the fan, because the calculated variations in heads and temperatures had the same trend as measured in an observation well. High permeable cells, which are connected with the river bed, influence selective flow significantly. A block averaged model with the five-meters resolution was also examined. As a result, outputs of vectors and contours were much uniformed and smoothed, because anisotropy in macro cells was disregarded. It was revealed that the high resolution model was effective and necessary for capturing more detail and actual groundwater flow field in an alluvial fan.