74 The Future of Water in African Cities
for capacity focus on governance, institutional setup and planning, and economic development. The limitations in the data gathered highlight the need for larger and broader based efforts to generate, collate, and pre sent comparable data at the city level. Despite data issues and the disparities among cities a few conclusions stand out. The need for a safe and continuous water supply for growing populations meets the reality of old and poorly functioning infrastructures in many cities in Africa. Nonrevenue water exceeds 40 percent for 18 of the 31 cities,5 indicating that systems are old and poorly maintained. Forty percent of the utilities have an operating ratio inferior to 100 percent,6 meaning that their revenues do not cover their operating costs; and for two-thirds of them (68 percent), the operating ratio is less than our benchmark of 130 percent, meaning that they are struggling to cover their costs. Of the 31 cities surveyed, only five cities have a sustainable rate of bill collection (defined as a 95 percent collection ratio).7 In many cities, ensuring good governance and adequate financing will be critical to upgrading old infrastructure and extending service to new areas. Population and water demand are growing very rapidly in some cities. The population in 17 of the 31 cities is growing at an annual rate of more than 3.7 percent. This is equivalent to a doubling time of 19 years. Of these 17 cities Abuja, Kumasi, Luanda, Ouagadougou, and Yaoundé exhibit growth rates of more than 5.3 percent per year. A growth of 5.3 percent is equivalent to a doubling time of 13 years. If income grows as well, water demand might double in 10 years or less. This exacerbates the challenges of water management and highlights the need to explore diverse water sources, including reused wastewater, to ensure that water is fit for purpose and to exploit innovative technologies. Certain cities are in areas that are naturally freshwater scarce (for example, Johannesburg) whereas other cities are in areas that have abundant natural water availability (for example, Kinshasa). Cities in arid or semiarid regions might abstract water from a distance (for example, Johannesburg and Nairobi); pump from artisan groundwater deposits (for example, Dar es Salaam); or, for coastal cities, exploit seawater that is abundant but costly to use. In all these cases, the engineering challenges and the cost of securing water are likely to be high. There are a few exceptions, such as Khartoum, of cities in arid regions located on major rivers. Many cities have high population densities, and a large proportion of residents live in informal settlements. Of the 31 cities in this study, 14 have a population density of more than 8,000 inhabitants per square