Henry Russell is known to have made the first ascent of the Pic Carlit in 1864, where he was fascinated by the beautiful view of the Étang du Lanoux, which can be seen from the top.

[2][3] The French Government proposed to carry out certain works for the utilization of the waters of the lake and the Spanish Government feared that these works would adversely affect Spanish rights and interests, contrary to the Treaty of Bayonne of May 26, 1866, between France and Spain and the Additional Act of the same date.

Before entering Spanish territory, the waters of the Carol feed the Canal of Puigcerda which is the private property of that town.

On September 21, 1950, Electricité de France applied to the French Ministry for Industry for a concession, based on a scheme involving the diversion of the waters of Lake Lanoux towards the River Ariège.

The Tribunal decided that in carrying out, without prior agreement between the two Governments, works for the utilization of the waters of Lake Lanoux in the conditions mentioned in the Scheme for the Utilization of the Waters of Lake Lanoux, the French Government was not committing a breach of the provisions of the Treaty of Bayonne of May 26, 1866, and the Additional Act of the same date.