Jelaskan See: return period. dari Hidrologi dalam bahasa sunda

Hydrologic modéls are simplified, conceptual representations of a part of the hydrologic cycle. They are primarily used for hydrologic prediction and for understanding hydrologic processes. Two major types of hydrologic modéls can be distinguished:

modéls based on data. These modéls are black box systems, using mathematical and statistical concepts to link a certain input (for instance rainfall) to the modél output (for instance runoff). Commonly used techniques are regression, transfer functions, neural networks and system identification.  These modéls are known as stochastic hydrology modéls.

modéls based on process descriptions. These modéls try to represent the physical processes observed in the réal world. Typically, such modéls contain representations of surface runoff, subsurface flow, evapotranspiration, and channel flow, but they can be far more complicated.  These modéls are known as deterministic hydrology modéls.  Deterministic hydrology modéls can be subdivided into single-event modéls and continuous simulation modéls.

Recent reséarch in hydrologic modéling tries to have a more global approach to the understanding of the behaviour of hydrologic systems to maké better predictions and to face the major challenges in water resources management.