The Río Duqueco originates in the Sierra Velluda in Chile's Biobío Region and flows generally westward for approximately 120 kilometers before joining the Río Biobío on its right bank near the town of Negrete. The river drains a watershed of roughly 1,350 km², with a mean discharge of around 60 m³/s, making it a river of substantial and relatively consistent volume.

In its upper reaches, the river passes through mountainous terrain with steep valley sides and broken ground before descending onto the central plain southeast of Los Ángeles, where the banks flatten and the current moderates. This transition from a more confined, faster-moving upper section to a broader, calmer lower section gives the river a notably different character depending on where one paddles. The river traverses the comunas of Quilleco, Santa Bárbara, and Los Ángeles along its course.

The watershed is divided into five sub-basins, with the largest segment — between Estero Quilleco and Río Coreo — covering over 57,000 hectares. Several tributaries join the Duqueco along its length, including Rucanahuel, Villucura, Quilleco, Curiche, and Paillihue. Near its headwaters, the area around San Lorenzo is noted for mineral waters. The river ultimately splits into two channels before reaching the Río Biobío opposite Negrete.

The river falls under Chile's secondary environmental quality standards for the protection of continental surface waters of the Río Biobío basin, which establishes a regulatory framework for water quality in the watershed. Beyond this framework, no specific paddling restrictions or access point details have been documented, and paddlers planning a trip should verify local access conditions and any applicable regulations before launching.