ABSTRACT
Because the study of processes is relatively recent, there is still a certain amount of confusion about the terminology used to name them. So in this chapter, whenever we discuss a process, we will mention the various terms by which it is known. In general, the processes governing flow are poorly understood. This is due in part to the fact that there are many different answers to the main two questions in hydrology. Therefore, this chapter will try to answer – at least in part – these two questions: “What is the future of rainfall water?” (Penmann, 1963) and “What is the source of the water in rivers?” (Hewlett, 1961), by identifying the four main paths that water travels into the rivers as proposed by Ward and Robinson (1990), and illustrated in Figure 11.1:
1. Direct precipitation Pd on the surface of a waterbody.
