Development and population growth are increasing the pressure on natural resources, particularly water. In recent, limitations on water quantity and/or quality have led to numerous conflicts world-wide. The limitations on water availability make it necessary to increase the efficiency with which water is used. Irrigated agriculture, industry and residential are the primary destination of the worlds fresh water supply. In semi-arid environments, irrigation alone can account for 80% of the regional water use. Overland flow is present extensively in water conveyance and water use. Indeed, most water conveyance, natural and man-made, is performed in overland flow, such as in rivers and canals.

In the last decades, overland flow modelling has been an active field of research. Developments in numerical methods and computational resources have led to a series of models applicable to different geometries and types of flows. At the present time, overland flow modelling is facing the challenges dictated by new numerical approaches, the simulation of canal and river networks, the need to achieve high irrigation management standards, the conservation of riparian areas, and the control of pollution and eutrophication of surface and ground waters.

Hydraulic Engineering becomes necessary to answer most of these problems and most specifically Computational Hydraulics. This field of research is concerned with the study of the flow dynamics using numerical solutions of the non linear equations that describe the physical processes. The computer becomes the essential tool to perform those calculations. The water movement is assumed governed by fundamental principia that can be expressed in mathematical terms and often adopt the form of partial differential equations. The main focus is in the ability to solve those equations and be able to obtain complete descriptions of the flow field in space and time with the help of computers.