In most developing countries,two-thirds or more of the people live in rural areas,with few,if any,of the services the city-dweller takes for granted.Water taps in houses,for example,are almost unknown.At best,there may be a village well.Often the only source of water is a lake or a lake or a stream,perhaps several kilometers away.The drudgery of water-carrying can take up the better part of every day.