A range of 20 to 40 liters of freshwater per person per day is generally considered to be a necessary minimum to meet needs for drinking and sanitation alone, according to Peter Gleick, president of the Pacific Institute for Studies in Development, Environment and Security. If water for bathing and cooking is included as well, this figure varies between 27 and 200 liters per capita per day (73).

Several different amounts have been proposed as minimum standards. Gleick proposes that international organizations and water providers adopt "an overall basic water requirement of 50 liters per person per day" as a minimum standard to meet four basic needs—for drinking, sanitation, bathing, and cooking. In 1990, Gleick estimates, 55 countries with a population of nearly 1 billion people did not meet this standard as a national average (73). Falkenmark uses the figure of 100 liters of freshwater per capita per day for personal use as a rough estimate of the amount needed for a minimally acceptable standard of living in developing countries, not including uses for agriculture and industry (65, 69, 73) (see Chapter 3.1, Population Growth, Water Shortages).

The amount of water that people in a country actually use depends not only on minimum needs and how much water is available for use but also on the level of economic development and the extent of urbanization. Globally, of the three standard categories of freshwater use—for agriculture, industry, and domestic (personal, household, and municipal)—agriculture dominates. On a worldwide basis, agriculture accounts for about 69% of all annual water withdrawals; industry, about 23%; and domestic use, about 8% (49, 53, 168, 176).

There are wide differences by region. In Africa an estimated 88% of all freshwater use is for agriculture, 7% for domestic purposes, and 5% for industry. In Asia water also is used mostly for agriculture, estimated at 86% of total use, while industry accounts for 8%, and domestic use, 6%. In Europe, however, most water use is for industry, at 54%, while agriculture accounts for 33%, and domestic use, 13% (53).

Freshwater and economic development. A country's level of freshwater use reflects—and, in fact, is one of the key measures of—its level of economic development. In developing regions of the world people use far less water per capita than in developed regions. In Africa annual per capita water withdrawals for personal use average only 17 cubic meters (equal to 47 liters of water per day), and in Asia, 31 cubic meters (equal to 85 liters per day) (30, 111). In contrast, comparable water use in the UK is estimated at 122 cubic meters per year (334 liters per day), and in the US, 211 cubic meters per year (578 liters per day) (53).

Developing countries devote most of their water supplies to agriculture. India, for instance, uses 90% of all water for agricultural purposes, with just 7% for industry, and 3% for domestic use (53). The higher the level of development, the more water is used for domestic and industrial purposes and the less for agriculture. There are some important exceptions to this rule, however. For example, Japan still uses the largest share of its freshwater for irrigating rice. Also, in some arid areas of Europe, such as Spain and Portugal, most of the available water is used for irrigated agriculture (75).

Around the world freshwater demand per capita is rising substantially as countries develop economically. Withdrawals of water have grown in all three major categories of use—to meet rising industrial demand, rising domestic demand, including for municipal use, and increasing reliance on irrigation to produce food (174) (see Figure 4).

Urbanization. The level of water use also reflects the level of urbanization in a country. Low household water use in many developing countries today often reflects difficulty in obtaining freshwater. Piped water systems are rare in rural areas. Two-thirds of the world's population, the majority in developing countries, get their water from public standpipes, community wells, rivers and lakes, or rainfall collected off roofs. Often rural people—usually women and girls (214)—must walk many kilometers and spend many hours fetching water for their households. In Africa, for instance, women and girls spend 40 billion person-hours a year hauling water (188).

Urbanization increases water use dramatically. For example, in 1900 the average American household used as little as 10 cubic meters of water per year compared with more than 200 cubic meters today (53). Why? A century ago, most Americans obtained their freshwater from wells or public standpipes. Running water was largely unavailable to households except in big cities, and most people lived in the rural areas. In contrast, virtually every American household today has running water available, and this water costs its users very little.

As the world becomes predominately urban, while agriculture depends more and more on irrigation, it will be difficult for cities to meet the rising demand for freshwater. In developing countries rapid urban growth often puts tremendous pressure on antiquated, inadequate water supply systems. For instance, between 1950 and 1980, the populations of many cities in Latin America, such as Bogota, Mexico City, São Paulo, and Managua, tripled or even quadrupled. Such African cities as Nairobi, Dar es Salaam, Lagos, and Kinshasa grew sevenfold, primarily because of a rural exodus. In the 1990s cities of developing countries have had to cope with about 60 million new arrivals every year (63, 68). Yet many agencies are not equipped to manage the urban water supply, while some countries have ineffective water allocation systems that allow cities to run short of water at the same time that water resources are being used for subsidized agriculture (130).