 Traditional ecological knowledge is the understanding of ecological information which reflects human experience with nature. This knowledge is often developed and gained over centuries and is passed on from generation to generation. Rainwater harvesting practices date back almost 5000 years and are found all over the world. Water harvesting is the collection and storage of rainwater in natural or constructed reservoirs. These techniques are categorized into microcatchment and macrocatchment harvesting systems. Microcatchment systems collect surface runoff over a short distance in a small catchment area. On-farm systems collect rainfall right where it falls and make sure that the crops use the water effectively. Proof-top and courtyard harvesting systems collect and store rainwater from buildings, greenhouses, courtyards etc. to use for agricultural or domestic purposes. Macrocatchment harvesting systems are characterized by comparatively large catchment areas to collect runoff water, for example from mountainous regions. These systems harvest water from long slopes and external catchments. A long-use technique is the on-wadi system. In this type of system the valley bed is used to store water, either on the surface with water flow blockages or inside soil layers by slowing down water infiltration. Off-wadi systems apply the harvested rainwater outside the wadi bed. In these systems structures divert the rainwater from its natural pathway into a close by area suitable for agriculture. It is important to come up with models and methodologies that promote indigenous knowledge on rainwater harvesting to reinforce and strengthen rainwater harvesting systems. Reviving and sharing knowledge on traditional rainwater harvesting can improve the water and food security of the world, especially in climatically and agriculturally challenged regions.