This chapter explores empirical data on the behavior of water, contaminants, and heat in the unsaturated zone. The purpose is to understand the unsaturated zone system so that conceptual and ultimately mathematical models can be developed.
In a few cases, simple lumped models describing the unsaturated zone behavior will be presented. These models often serve as a basis for conceptualization and for describing complicated boundaries such as the land surface boundary condition required to solve more complicated equations of flow, Chapter 6. Or in the case of lumped time-of-travel models, provide rough estimates of the magnitude of the time scales in contaminant transport problems.