The headwaters of the river are found in the mountains of Davao de Oro, near its border with Davao Oriental and east of Tagum. 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.[5] It finally drains into the Butuan Bay at its mouth in Butuan.