[A-HW22] 流域生態系における物質輸送と循環：源流から沿岸まで

[AHW22-15] Water discharge at forested watersheds throughout Japan by using SWAT

*今村 直広¹、Wang Kunyang²、小野寺 真一²、清水 裕太³、小林 政広¹、清水 貴範¹、山下 尚之¹、篠宮 佳樹¹、玉井 幸治¹、澤野 真治¹、飯田 真一¹、壁谷 直記¹、清水 晃¹、坪山 良夫¹ (1.森林総合研究所、2.広島大学、3.農業・食品産業技術総合研究機構)

キーワード：水流出、SWAT、森林流域

Predicting the impact of forest operations and/or climate change on water and nutrient cycle in forest watershed are more important for planning future forest management in Japan. This study estimated daily water discharge at different sizes and different climate watersheds in Japanese forested areas by using SWAT. We calculated discharge at Jyozankei (1.9 ha) in snowfall area (Abe et al., 2010; 2011; 2014; Nobuhiro et al., 2020), Katsura (60 ha) and Tsukuba (3.8 ha) in a temperate area, and Kahoku (3.7 ha) and Takatoriyama (19 ha) in heavy rainfall area. As a result, daily hydrographs showed relatively high reproduction for observed values at all watersheds (Nash-Sutcliffe efficiency (NSE) showed over 0.65 value). This means SWAT can calculate water discharge at various size forested watersheds in the Japanese climate. However, the calculated peak water values were a little low compared to the observed value. This indicated discharge in stormflow periods did not reproduce effectively. Setting distribution of soil depth in the watershed may be more important for improving water discharge in small forested watersheds.