Wetting phenomena when freezing a rivulet*

We experimentaly explore the freezing of a water capillary river flowing down a cooled inclined plane. In the first moments, we observe two different wetting phenomena taking place transverse to the streamwise direction. First, an ice footprint is left behind by the main droplet running down the inclined plane. Second, on top of the ice footprint, the remaining water film surprisingly dewets the ice on which it flows. The unsteady dewetting dynamics ultimately relaxes towards a steady state. We characterize the dependency of these two events against the substrate temperature and the water flow rate. Finally, we bring new understandings to two fundamental debated questions: the arrest of a contact line in the presence of solidification and the contact angle of water on ice.