Rainfall - runoff relationship in small mountainous catchments

The singular phenomenon of flow instabilities was observed in a small catchment: in some situations, the water supplied by rain caused a pronounced decrease in the soil water content. This soil water movement can be explained by assuming an irregularly oscillating outflow of soil water into lower horizons. In these situations a large volume of water flows through the soil; on the hydrological scale, this phenomenon forms a great part of the outflow from a watershed. The phenomenon can be described in the frame of the instability driven flow theory and explained as consequence of the porous soil bodyŽs capacity to become conductive in results of a very little change of its moisture. In this way, the soil profile can attenuate or amplify the rainfall pulses during their transformation to the outflow