ABSTRACT
The field of hydrology covers a vast and complicated domain. This chapter provides methods or procedures for performing hydrological calculations, but to alert the reader to the many different aspects and applications of this important discipline. At the outset, it should be appreciated that the movement of water within the hydrological cycle is a deeply stochastic process. All stochastic phenomena follow a statistical distribution. Statistical distributions are such that more data points are clustered around the average, with the data points getting scarcer as one moves away from the mean. Precipitation is a general term which includes rain, snow and frost. Coordinated rainfall measurements are made at many locations throughout South Africa. Most are made on farms, supplemented by numerous sophisticated weather stations with automatic and continuous recording of rainfall intensity, typically found at airports, dams and national parks.
