Arroyo Ñireco is a small, intimate stream tucked within the northern Neuquén region of Argentine Patagonia, flowing entirely through the lands of Estancia Chochoy Mallín. Born from Lago Lauquén Mallín at approximately 1,800 meters above sea level, the stream winds for 34 kilometers before emptying into the Río Reñileuvu at around 987 meters elevation. Along its course, it receives additional water from mallines (Patagonian wetlands) and smaller tributaries, which helps maintain a remarkably consistent flow throughout the fishing season. The name itself comes from Mapudungun, the language of the indigenous Mapuche people — "ñire" referring to a native hardwood tree and "co" meaning water, making Ñireco essentially "River of the Ñire Tree." The stream runs clear year-round, offering sight-fishing opportunities in a setting defined by low cutbanks, willows, shrubs, and mid-sized cobble — a classic small Patagonian spring-fed stream with a personality all its own.