Improving household agriculture with roof-harvested rainwater : a case study in Sydney and Nairobi

The production and distribution of a sufficient quantity of food and water of satisfactory quality is at the heart of sustainable development. At the small domestic scale, roof-harvested rainwater can make a significant contribution to food supply and distribution systems (production, handling, storage, and transportation). In this paper, we compare the potential crop production of a small garden plot using three methods of watering: (1) rainfed only with no irrigation; (2) irrigated with the ideal amount of water; and (3) rainwater tanks of various sizes installed and used to irrigate the plot. Yield was determined on the basis of the yield calculation method presented in FAO 33. It was found that yields can be increased considerably by installing a correctly managed rainwater storage system (RSS). A 3 kL RSS connected to a 120 m2 roof can increase yields in Nairobi from 40 kg to 96 kg. In Sydney, a larger roof of 200 m2 can increase yields from 66 kg to 143 kg. This study makes an important contribution to water and food security-related sustainable development goals.