Río de los Patos flows through the dramatic Andean landscapes of the Calingasta Department in San Juan Province, Argentina, carving its way through some of the most rugged and visually stunning terrain in the country. This mountain river is fed by snowmelt and glacial runoff from the high Andes, giving it the character of a classic freestone river with cold, clear water and a dynamic, boulder-strewn channel. The river ultimately contributes to the formation of the Río San Juan, joining with the Río Castaño and Río Blanco in the lower reaches. Sport fishing along the Río de los Patos remains relatively undiscovered compared to more famous Patagonian destinations, offering anglers willing to embrace the remote and challenging nature of San Juan's rivers a genuinely wild and rewarding experience.