Lake Lacar is located at approximately 40 degrees of south latitude and 71 degrees of west longitude in the province of Neuquen. The lake is embeded in the Andes Mountains Range and surrounded by a mountainous region, ranging 1,600 to 1,900 m. This stretched area contains in its interior the lake, which is a lacustrine hollow that occupies the lowest zone.

The basin of the lake extends towards the east up to San Martin de los Andes and Maipu. Towards the west the Nonthue lake forms its natural prolongation, being separated from the principal flow by a narrow valley. Towards the northwest it extends through the valley of Hua-Hum River, which cross the boundary with the Republic of Chile and goes into the Chilean territory.

Lake Lacar, as well as other basins which have a glacial origin, is characterized by the typical erosion of the ice in its surroundings. Its water surface is placed at 630 m above sea level.

Several rivers and streams come from the mountainous zone which is adjacent to the drawdown occupied by the lake and they come out through the Hua-Hum River. It has been estimated that the hydrographic basin of this drawdown has an area of 1,048 km2. No flux measurements are made in this river as it turns impossible to reach it by land. The only information available is the estimation made by Engineer Figueroa Bunge (CFI, 1961) who said that it had a mean flux of 50 m3 sec-1 at the boundary between Argentina and Chile.

The drainage basin of the lake is almost uninhabited, with the only exception of the northeast coast where San Martin de los Andes city is located. This city has about 12,000 inhabitants and its economy is based on tourism. The main activities are sport and recreational, the most important of them are hunting, fishing, sailing, ski and other aquatic sports.