gutter downspout drainage pipe

My landscaping contractor is using perforated and corregated plastic pipe to carry downspout drainage away from the house. The pipe is to lay in a shallow ditch, covered with river rock. For the first 20 feet, the pipe is nearly level and parallel to the house. I am worried that more water will leak into the ground (note: all of this work is to remedy a water-in-basement problem). Should solid or perforated pipe be used in this application, and will the water in the drainage pipe freeze during the Colorado winter (5400) if it is not burried beneath soil?