Challenges for water sustainability in Africa

Abstract

Water lies at the heart of many of Africa's problems. Although Africa as a whole is only slightly below the world average in terms of the available water resources per capita, and better off than Europe or Asia, it is beset by three critical groups of problem, one largely natural, the second very definitely manmade, the third somewhere in-between. The first centres on the distribution and reliability of resources. The second is related to the distribution and growth in human population. The third is the intimate link between water and disease in Africa, and the widespread lack of access to safe drinking water amongst the poorer communities. Much of the water that is theoretically available is either naturally dangerous for human health or else polluted by human activities lack of sewage treatment or pollution from agriculture, mining and industry. Despite the WHO's International Drinking Water Supply and Sanitation Decade in the 1980s, and the WHO's continuing Water, Sanitation and Health activities, the numbers without access to safe water continue to grow (WHO, 2004 website). Over 300 million still lack access to safe water in sub-Saharan Africa. Lack of access to safe water is worst in rural areas, where women and children often spend considerable time fetching water: over 1 .2 billion people worldwide live more than 1 5 min walk from a safe water source, many in Africa (Rodda, 1994). In the Southern African Development Community, 56% of rural communities lack access to safe water, against only 22% in urban areas. High temperatures favour the proliferation of many microbes as well as vectors of disease like the Anopheles mosquito. It is estimated that if malaria had been properly tackled 30 years ago when effective control measures first became available, Africa's GDP would now be about $100 billion greater (World Health Organisation, 2001). Public health is, therefore, not solely a question of safe water provision, but also of sound management of the water environment in order to control all water-related disease. Together, these factors make the average per capita water resource statistic largely meaningless in practical terms. Africa's climatic location is a fundamental source of its problems. Straggling the equator and extending beyond both tropics, the climates of Africa are dominated by the Hadley Cells. These circulation cells create both the excessive rains on the rising limb along the Intertropical Convergence Zone around the equator and the desiccation of the adiabatically heated air on the sinking limb around the subtropics, which suppresses convective activity and rain formation. This results in a grossly uneven distribution of water resources, ranging from desert to equatorial rainforest. Fluctuations in the strength of the Hadley Cells, their associated monsoons and other elements of atmospheric circulation in the tropics, like the Biennial Oscillation and the Southern Oscillation, also result in considerable and often critical unreliability of rainfall throughout much of the continent. To this is now being added clearly discernable climatic change, some perhaps natural, some apparently related to human-induced global warming. The frequency of drought appears to have increased in recent decades, particularly in the Sahel and the Horn of Africa. Drought in tropical Africa is often associated with the reversals of ocean currents in the equatorial Pacific known as El Nino, which have been getting more intense in recent years. At the same time, there have been some unusually intense tropical cyclones emanating from the western side of the Indian Ocean in the southern hemisphere. The hurricane seasons in 1999-2001 were especially problematic: the worst event for 50 years occurred between January and March 2000, when Cyclones Eline, Gloria and Hudah saw 150,000 ha flooded in Mozambique, hundreds killed and over 1 .25 million made homeless in southern Africa, including Botswana, South Africa, Zambia, Zimbabwe and Madagascar. There are, however, some more purely human elements in the increasing frequencies of droughts and flood disasters. Overgrazing, deforestation and devegetation have created long-term changes in the water balance of many desert margins, increasing the proportion of rainfall draining away as storm runoff, thereby increasing flood problems, eroding the top soil, reducing soil moisture retention and decreasing the recharge of aquifers. The eminent climatologist, Reid Bryson, has even suggested that increased dust from agricultural activity in semiarid regions has increased the atmospheric albedo or reflectivity, cooling the upper air and so inducing air subsidence which suppresses potentially rain-creating convective cells even further (Bryson and Murray, 1977). The net result has been that the West African monsoon has penetrated less far northwards into the Sahel in recent decades, aggravating the incidence of drought and famine. Similarly, the devastating Nile floods of 1988 were created by a combination of the 1000-year rainfall event and more rapid runoff caused by deforestation in the headwaters. Floods like these also carry risks for public health, increasing the incidence of diarrhoea, dysentery, cholera