SOIL WATER REGIME IN HEAD WATER REGIONS - OBSERVATION, ASSESSMENT AND MODELLING

Abstract

The present article demonstrates the impact of water content in the soil profile on the formation of rain -water outflow below the soil profile. The example of the soil water regime during the vegetation season is applied to show two alternative types of soil water movement: the diffusion type flow (DTF) in drier soils and the instability-driven flow (IDF) in soils with a higher soil moisture content. This responds to t wo phases of soil water regime alternation – the percolation phase (IDF is taking place) and the accumulation phase (DTF is taking place). In the course of the percolation phase, the infiltrating rain water flows through the soil without causing any considerable increment of water content in the soil profile. During the accumulation phase rain water accumulates in the soil, without practically flowing through the soil profile. The soil profile functions like a reservoir filled with rain water and emptied by the withdrawal of water for plant transpiration.