The dam was built in 1976[1] to collect rainwater and water from the Pyrenees for agricultural use during the dry summers that are common in this area beyond the Lannemezan plateau.

It spans the Arrats valley, and has a spillway on the east side of the dam to evacuate excess water.

The former, unlike the latter, is fed by the Neste canal[fr], which contributes all year round to the river's low-water level.

[3] Recently, the Lac de l'Astarac was included in the Natura 2000 network of the Lauze[fr] valleys and hillsides, further protecting the flora and fauna of the area.

[4] Lac de l'Astarac is home to rich biodiversity, particularly from an ornithological point of view, as it is a migratory stopover or wintering area for many bird species.