SOIL-WATER CHEMISTRY DEPENDENCE ON WATER PATHWAYS AND TURNOVER

Water flow and transit in the soil are important to water supply and t ransport of chemical compounds. Flows through forested till soils are by vertical percolation in the upslope areas, groundwater flows along the slope to discharge in downslope sites. The flow is divided into sl ow and fast parts both in the unsaturated percolation and the saturate d groundwater. Soil development influences the flow and in coarse grai ned and well drained soils groundwater flow is stable but in finer gra ined physically stratified soils, variations in flow are considerable. Large flows occur in the upper soil layers and small flows in deep la yers. Chemical composition of soil water varies in a similar way. In t he upper layers, water is more acid and has a lower content of base ca tions compared to deeper layers. In downslope areas discharging deep g roundwater contributes to less acidic conditions also in the upper soi l layers. This discharge and a dominating lateral water flow in the up per layers partly protect deep layers from acidification which is emph asised by slow water turnover in these layers.