In spite of being a short river, its drainage basin is the seventh-largest in the country due to the great size of the O'Higgins/San Martín Lake, its source.

The river flows quickly forming rapids until it creates a cascade in the place where it falls into the Chico Lake.

After leaving this lake, the river forms a new cascade and rushes furiously, preventing any type of navigation on its waters.

After 62 km, the Pascua River ends in a wide delta that empties into the Baker Channel, previously having rushed in a last area of rapids.

There exists a controversial Endesa project to construct two massive power dams on the course of the river, but the proposal has generated immediate opposition from a great part of the population and in the government authorities, due to the serious ecological damage that would cause in the zone.