|Rio Grande de Agusan|
The Agusan River from Butuan City in its view from Magsaysay Bridge.
Drainage basin of the Agusan River
Agusan River is a river in the Philippines. It is located in the north-eastern part of Mindanao island, draining majority of the CaragaRegion and some parts of Compostela Valley province. It is the country's third largest river basin (after Cagayan River and Rio Grande de Mindanao) with a total drainage area of 11,937 square kilometres (4,609 sq mi) and an estimated length of 390 kilometres (240 mi) from its origin. The headwaters of the river are found in the mountains of Compostela Valley, near its border with Davao Oriental and east of Tagum City. It flows through the wide Agusan River valley which measures 177 kilometers (110 mi) from south to north and varies from 32-48 kilometers (20–30 miles) in width. It finally drains into the Butuan Bay at its mouth in Butuan City.
One of the prominent features in the Agusan River basin is the presence of the Agusan Marsh covering a total area of 19,197 hectares. The marsh serves a flood retention basin for the Agusan River, cutting the high discharge of water causing flash floods in the lower reaches of the river. Aside from that, the marsh harbors unique and pristine habitats like the sago and peat swamps forest and is a home to endangered and endemic flora and fauna. As a consequence, it was declared by former President Fidel V. Ramos as a wildlife sanctuary in 1996.
The Agusan River basin is divided into three sub-basins on the basis of topographic features: upper Agusan River basin, middle Agusan River basin and lower Agusan River basin. The upper Agusan River basin is the section from its headwaters in the mountains of Compostela Valley province to Santa Josefa, Agusan del Sur to Veruela, Agusan del Sur, the middle Agusan River basin is the section of the river from Sta. Josefa to Amparo, Agusan del Sur while the lower Agusan River basin is from Amparo to its mouth at Butuan City, Agusan del Norte