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The Orosi River (Spanish pronunciation: [oɾoˈsi]), also called Rio Grande de Orosi, is a river in Costa Rica near the Cordillera de Talamanca. The watershed contains one of the rainiest areas of Costa Rica, with annual rainfalls of up to 710 centimetres (280 in). It goes through the Tapantí National Park and drains into Lake Cachi (Lago de Cachi), the site of the Cachi Dam (Represa de Cachi).