Author(s): Yoko Hirasawa; Makoto Nakatsugawa; Tomohide Usutani

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Keywords: Snowmelt; Distributed runoff model; Snow Depth Analysis; Runoff prediction; Water balance

Abstract: In this study, we proposed a method that enables year-round runoff calculation by calculating not only heavy rainfall but also snowmelt runoff, and verified its practicality in several dam basins. The method calculates rainfall-snow discrimination and snowmelt runoff using Radar-Raingauge Analyzed Precipitation, Analytical snow depth, and the Meso-Scale Model GPV (MSM), which are distributed by the Japan Meteorological Agency. The topographic data used in the calculations are global flow direction data, and runoff calculations can be performed for a watershed with an arbitrary point as the downstream end. Both data are publicly available or distributed data, and the flow rate of any basin can be predicted in real time throughout the year, including the snowmelt season, without any special observation or forecast data. Furthermore, to minimize errors caused by weather forecast data, the method incorporates the latest analytical rainfall data available by the time the weather forecast data is distributed. Verification confirmed the validity of the water balance and the reproduced annual runoff heights as a result of the long-term replicated calculations. By using the values obtained from the long-term slope runoff calculations as the storage height of the tank model, the wetting of the soil at the initial time can be taken into account in the predictive calculations. Prediction calculations showed that the 24-hour integrated runoff heights were generally predictable for both the summer and snowmelt cases. The predicted runoff, which can be used throughout the year in snowy and cold regions, will be useful to improve water use efficiency while maintaining disaster prevention functions.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1986-cd

Year: 2025