|The hydrology studies the water cycle - an occurrence and amount of water, its circulation and its temporal and spatial distribution. The water cycle is extremely complicated and incorporates a large number of partial processes, from which only a part is described and quantified. The main goal of hydrology is therefore the description of the water cycle and related processes. Nevertheless, from the practical point of view there is also a strong need to model these processes. A lack or an excess of water are limiting factors for many human activities, therefore the hydrological models are used in many areas, e.g. in the urban or landscape planning, within the flood warning systems etc.
A hydrological model is a computer programme simulating the hydrological cycle or its part. Any model is always a simplified representation of the reality, nevertheless it must capture the significant characteristics of the modelled process with a sufficient accuracy. There is a large number of hydrological models which can be classified into three groups according their inner structure:
- Physically based models – an inner structure corresponds well to the reality, usually they are driven by a set of partial differential equations. The computation is very time demanding, the models are suitable for the design purposes or for the delineation of flood areas.
- Conceptual models – an inner structure approximately corresponds to the reality, nevertheless the model physics is very simplified. These models represent a compromise between the physically based and the black-box models and they are applied in many areas.
- Black-box models – represent a pure mathematical input/output transformation without any physical basis. The regression models, the neural networks or the fuzzy models are the examples of this group. They are suitable for operational purposes (e.g. warning systems).