ABSTRACT
The previous chapter reviewed the components of the water balance and the processes involved in converting “inputs” of precipitation and energy into “outputs” of evaporation, runoff and groundwater recharge. Different sets of processes operate in different places and at different times during the year, on inputs which also vary over space and time, in catchments which have variable physical characteristics. These layers of variability mean that patterns of evaporation, runoff and recharge also vary over space and time. This chapter explores these patterns, at the global scale, focusing particularly on runoff and recharge. First, however, it is important to review the many measures used to characterise hydrological behaviour. “Hydrological behaviour” is defined here to mean a pattern of variation both through the year and from year to year. The term “flow regime” is widely used in the hydrological literature, and tends to refer to patterns of variation through the year.
