The most feasible reuse of rainwater in urban areas is for irrigation, which may account for 35 to 50% of domestic water use in Canada and the US; other uses may be restricted by local regulations. Cowden et al. (2006) estimate that domestic rainwater harvesting could improve the per capita access of African urban slum dwellers to water, in the range of 20 to 50 L/d during at least three months of the year. A major limitation of rainwater reuse is the limited reliability of supply (depending on rainfall occurrence), which can be improved by adding storage to the reuse system.