Embalse Dique de Ullum is a striking reservoir nestled in the Quebrada de Ullum canyon, approximately 18–20 kilometers west of the city of San Juan in the Cuyo region of Argentina. Formed by the Quebrada de Ullúm Dam — an earth and rock-fill embankment dam completed in 1980 on the Río San Juan — the reservoir sits at an elevation of 768 meters above sea level and covers a surface area of 32 square kilometers. With a total storage capacity of 440 million cubic meters, an average depth of 15 meters, and a maximum depth of 40 meters, this is a substantial body of water set against a dramatic backdrop of arid canyon walls and semi-desert terrain. The dam serves multiple purposes: regulating irrigation water for the 800 km² Valle del Tulum agricultural zone, supplying drinking water to the greater San Juan metropolitan area, and powering the Ullúm hydroelectric station. Over the decades, the reservoir has evolved into one of the province's premier recreational destinations, drawing anglers, water sports enthusiasts, and hikers to its shores year-round.