Abstract
This study evaluates the regional modeling of drought river discharges in a unit area for a variety of watersheds, Hokkaido Island, Japan, and illustrates its present and future maps under the climate change condition. An initial linear model for drought discharge data in 115 watersheds consists of 44 parameters covering the areas of precipitation, temperature, geomorphology, geology, vegetation, soil, and land use. The parameters are extracted step by step in terms of parameter numbers and residuals in partially least squares. As a result, the regional model is obtained with 11 parameters; total snowfall in winter, total rain-falls in winter and autumn, temperatures in winter and summer, standard deviation of elevation, averaged surface slope, areal ratios of Quaternary volcanic deposits and rocks, and of forests and wetlands. The coefficients in the regional model contribute to interpret the factors controlling drought discharges in the snowy cold island. The present drought discharges at 1152 watersheds are calculated by the regional model, and are mapped in the GIS procedure. The prediction map of drought discharge when the global mean temperature would increase by 2K is also illustrated by inputting previous simulation results of precipitation and temperature into the regional model.
