Kapillärtillströmningen

Kapillärtillströmningen, or capillary fringe, refers to the zone in the ground where groundwater rises by capillary action from the phreatic zone into the pores of the unsaturated zone. This phenomenon is driven by the adhesive and cohesive forces between water molecules and soil particles, as well as among water molecules themselves. In this zone, the pore spaces are not fully saturated with water, and the water pressure is negative, meaning it is less than atmospheric pressure.

The thickness of the capillary fringe varies significantly depending on the soil type and the size of the soil pores. It is typically thicker in fine-grained soils like silt and clay, where the pores are smaller, allowing for greater capillary rise. In coarser soils like sand and gravel, the pores are larger, and the capillary fringe is much thinner or may be practically absent. The water table represents the upper limit of the saturated phreatic zone, and the capillary fringe extends upwards from this boundary.

Understanding the capillary fringe is important in various fields, including hydrology, soil science, and civil engineering. It influences the moisture content of the soil above the water table, affecting plant growth, soil stability, and the movement of contaminants. In agricultural contexts, the capillary fringe can be a source of water for shallow-rooted plants.