river, northeastern Ecuador, rising south of Tulcán, in the Andes mountains near the Ecuador-Colombia border, and flowing east-southeast for approximately 230 miles (370 km) to its juncture with the Napo River at Pantoja. It is navigable for smaller boats. The Rio de Janeiro Protocol of 1942 fixed the lower course of the Aguarico (Spanish: “Rich Water”) as part of the long-disputed Ecuador-Peru frontier. Although Ecuador unilaterally denounced the protocol in 1960, a new agreement was signed in 1998.