Generally the term “water harvesting� comprises many techniques that are used to supply rainwater collected from surfaces (roofs, ground surface, rock surface) for domestic or agricultural use. It can be defined as “... the process of concentrating rainfall as runoff from a larger catchment area to be used in a smaller target area� (Oweis et al.,1999, p.2). Water harvesting techniques represent methods to provide water for irrigation, watering domestic smallstock or domestic purposes from other sources than (permanent) streams, rivers and pumped groundwater. Usually a rainwater system consists of three main components: a catchment area, a storage reservoir and a delivery system. The target area can be the soil profile of the cultivated area or some kind of reservoir or tank. Water harvesting is particularly relevant to areas where rainfall is insufficient to balance evapotranspiration of crops and to sustain a good pasture growth.