ADGEO Advances in Geosciences ADGEO Adv. Geosci. 1680-7359 Copernicus Publications Göttingen, Germany 10.5194/adgeo-35-55-2013 Simulating river discharge in a snowy region of Japan using output from a regional climate model Ma X. 1 Kawase H. 1 Adachi S. 1 Fujita M. 1 Takahashi H. G. https://orcid.org/0000-0002-1991-422X 1 2 Hara M. https://orcid.org/0000-0002-7012-4581 1 Ishizaki N. 1 Yoshikane T. 1 Hatsushika H. 3 Wakazuki Y. 4 Kimura F. 1 Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan Department of Geography, Tokyo Metropolitan University, Tokyo, Japan Toyama Prefectural Environmental Science Research Center, Toyama, Japan Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki, Japan 02 07 2013 35 55 60 Copyright: © 2013 X. Ma et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://adgeo.copernicus.org/articles/35/55/2013/adgeo-35-55-2013.html The full text article is available as a PDF file from https://adgeo.copernicus.org/articles/35/55/2013/adgeo-35-55-2013.pdf

Snowfall amounts have fallen sharply along the eastern coast of the Sea of Japan since the mid-1980s. Toyama Prefecture, located approximately in the center of the Japan Sea region, includes high mountains of the northern Japanese Alps on three of its sides. The scarcity of meteorological observation points in mountainous areas limits the accuracy of hydrological analysis. With the development of computing technology, a dynamical downscaling method is widely applied into hydrological analysis. In this study, we numerically modeled river discharge using runoff data derived by a regional climate model (4.5-km spatial resolution) as input data to river networks (30-arcseconds resolution) for the Toyama Prefecture. The five main rivers in Toyama (the Oyabe, Sho, Jinzu, Joganji, and Kurobe rivers) were selected in this study. The river basins range in area from 368 to 2720 km<sup>2</sup>. A numerical experiment using climate comparable to that at present was conducted for the 1980s and 1990s. The results showed that seasonal river discharge could be represented and that discharge was generally overestimated compared with measurements, except for Oyabe River discharge, which was always underestimated. The average correlation coefficient for 10-year average monthly mean discharge was 0.8, with correlation coefficients ranging from 0.56 to 0.88 for all five rivers, whereas the Nash-Sutcliffe efficiency coefficient indicated that the simulation accuracy was insufficient. From the water budget analysis, it was possible to speculate that the lack of accuracy of river discharge may be caused by insufficient accuracy of precipitation simulation.

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