ough a number have contracts to build and operate works. These include the risks to returns, local opposition and legal obstacles. They have however been increasing their co-operation and partnerships with Russian companies in the sector, providing engineering and consultancy expertise. The estimated investment required to replace water works and installations runs at USD 10 billion. To be able to cover such expenses over ten years would require tariff increases of 4 times present levels. In view of such high amounts other sources of funding need to be identified. For full water meter penetration an amount of USD 200 million has been estimated along with USD 50 million annually to service such a system. It has been anticipated that in the medium term there could be up to ten large local companies managing water services to the majority of Russian towns and cities. Africa Africa has the lowest proportional coverage of the population with access to improved water supply of any region of the world. The situation is much worse in rural areas, where coverage is 50% compared with 86% in urban areas. Sanitation coverage in Africa is also poor, although Asia has even lower coverage levels. Currently, only 60% of the African population has sanitation coverage, with 80% and 48% in urban and rural areas respectively. In global terms, the continent houses 27% of the world's population that is without access to improved water supply, and 13% without access to improved sanitation. The African population is expected to increase by 65% over the next 25 years, with the greatest increases in urban areas. The urban population is expected to triple, from some 138 million in 1990 to 500 million in 2020, with 20% of the population - some 200 million - living in a few megacities. In 1990 the largest megacities (25 million) accounted for half or more of the GDP. Meeting the 2015 MDG targets will require tripling the rate at which additional people gained access to water between 1990 and 2000, and quadrupling the rate at which they attai