Africa’s Emerging Urban Water Challenges 29
Figure 1.10 Buildings at Risk due to Gully Erosion, Omagba, Nigeria
Source: Nigeria Erosion and Watershed Management Project, World Bank (provided by Stephen Danyo).
swells in cities across Africa, now is the time to act to build resilient cities. Africa is exposed to multiple natural hazards, the intensity and impacts of which are likely to increase with climate change. Investing in disaster preparedness is critical for the lives and livelihoods of residents in times of crisis, as well as for ensuring a competitive city image necessary for attracting and sustaining economic activities. Africa’s climate is highly seasonal, and varies widely from year to year. The continent’s climatic zones range from humid equatorial, to seasonally arid tropical, to subtropical Mediterranean climates. Each climatic zone exhibits different degrees of variability in rainfall and temperature. Hydrological variability and extremes are at the heart of the challenge of achieving basic water security in Africa. Year-to-year and decade-todecade phenomena such as the El Niño Southern Oscillation also have a significant impact on African hydrology (Parry et al., 2007). The high variability of precipitation and temperature across Africa translates into widely varying runoff, with basins such as the Congo displaying extremely high runoff and the arid and semiarid regions of Egypt, the Sahel, Sudan, and southern Africa displaying very low runoff. Much of Africa also exhibits significant changes in runoff and flows within and across years. Although annual variability in rainfall is high in most of