Lake Biwa occupies one-sixth of Shiga Prefecture's land area, and the water flowing from the lake flows into Osaka Bay in the Seto Inland Sea through the Seta-gawa River, whose name changes to the Uji-gawa River and later the Yodo-gawa River.
滋賀県の面積の6分の1を占め、流れ出る水は瀬田川、宇治川、淀川と名前を変えて、大阪湾（瀬戸内海）へ至る。