1 Environmental Considerations With Respect to Rainwater Harvesting

Technical description Rainwater harvesting for domestic use is an option, which has been adopted in many areas of the Palestinian territories since ancient times. A rainwater harvesting system consists of three basic elements: collection area, conveyance system and storage facilities. The technology is based on small-scale rainwater catchments systems. As rainwater falls of a roof, the water flows through plastic pipes (4 “ VPC or plastic pipes) and into a large cistern. The collection area in all cases of domestic use is the roof of a house or building. The effective roof area and the material used in construction the roof influence the efficiency of collection and the water quality. The water ultimately is stored in cisterns, often excavated in the lime stone rock formation or in a storage structure, which may be part of the building. None of the rainwater harvesting systems uses any devices for filtration or disinfecting, but as a normal practice, the users divert the ‘first flush ’ water so that it does not enter the storage facility. This practice is normally implemented once at the beginning of the rainy season only. Roofing material Roofs in the majority of the building are made of concrete, or galvanized iron. Some are made of tiles or asbestos. Large portions of the roofs (over 65%) are insulated using heat welded asphalt sheets. Composite asphalt, asbestos and some painted roofs could leach toxic materials into the rainwater as it touches the roof surface. The asphalt roofing is not recommended for portable water supply. Washout of the asphalt material is common. In addition, mineralized asphalt roofing texture makes cleaning the catchments area prior to a rain event more difficult than it would be on smoother surface such as metal or concrete