- Hydrological modelling
**Hydrologic models**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 models can be distinguished:

* Stochastic Models. These models are black box systems, based on data and using mathematical and statistical concepts to link a certain input (for instancerainfall ) to the model output (for instancerunoff ). Commonly used techniques areregression ,transfer function s,neural networks andsystem identification . These models are known as stochastic hydrology models.

* Process-Based Models. These models try to represent the physical processes observed in the real world. Typically, such models contain representations ofsurface runoff ,subsurface flow ,evapotranspiration , and channel flow, but they can be far more complicated. These models are known as deterministic hydrology models. Deterministic hydrology models can be subdivided into single-event models and continuous simulation models.Recent research in hydrologic modeling tries to have a more global approach to the understanding of the behaviour of hydrologic systems to make better predictions and to face the major challenges in water resources management**Groundwater modelling****urface water modelling****Runoff model (empirical)**These models use an empirical method to convert rainfall volume into runoff volume. An example is the Curve Number method.

**Runoff model (reservoir)**These models describe rainfall-runoff relations using the concept of a (non)linear reservoir.

**Hydrological transport model**These models describe the flow and routing of water once it has entered a river/stream system and the transport of dissolved or suspended material and debris in a river/stream. Examples include

MIKE 11 , MOHID,WAFLEX and DSSAM.**Composite models**Many models combine two of these types, for example HBV, which is combines an emperical runoff model and a hydrological transport model. Some models combine elements of surface water models and groundwater models, for example

MIKE SHE .**ee Also***

Surface runoff

*Aquifer

*Water quality

*Wikimedia Foundation.
2010.*