Physical Processes Relevant to Deep Soil-Water Movement
This chapter presents a summary of the physical processes commonly encountered by groundwater hydrologists: infiltration, drainage, and redistribution. Infiltration is the process whereby water enters the soil from surficial sources, such as rainfall, snowmelt, flooding, irrigation, liquid waste spills, etc. The infiltration process in any geometry is controlled by many factors, such as the rate of water application, antecedent moisture in the soil, soil hydraulic properties, topography, and others. The moisture content of the soil prior to the rainfall also is an important consideration in predicting the infiltration rate or cumulative infiltration over time. Geologic heterogeneity must be kept in mind when interpreting infiltration and redistribution from water-content profiles. Owing to heterogeneity, the downward percolation of water during infiltration or redistribution may virtually cease where the infiltrated water migrating through a fine soil encounters a dry and relatively uniform, coarse-textured layer.