Global stressors on water quality and quantity.

This inequality is especially critical for Asia, which has 60% of the world’s population but only 36% of the world’s water. Water quality in terms of pollutant loading also is not distributed equally and is related to the type of use and a country’s level of development (Figure 2). Developing countries often have less capacity to improve water quality and depend on lower-quality water for a variety of uses, including drinking water. To capture an overall picture of a nation’s water use, researchers calculate the national water footprint; this represents the total volume of freshwater used to produce the goods and services consumed by a population and the impact of globalization by F or more than a decade, the scientific community as well as nongovernmental organizations have sought to raise an alarm concerning the unsustainable use of the planet’s available water resources (1). Rising world populations and consumption are inexorably increasing human demand for domestic, industrial, and agricultural water. Population and wealth along with other global stressors will have a direct and significant impact on the sustainability goals, technology selection, and governance strategies that are related to water quality and quantity. On a global basis, ~70% of freshwater is currently used for crop irrigation, ~20% for industrial purposes, and ~10% for domestic purposes (2). However, water use varies dramatically from one part of the world to another. Egypt, for example, uses 98% of its water for irrigation, leaving only ~27 L/capita-day for domestic use. In contrast, the U.S. uses 40% of its water for irrigation, and domestic water use exceeds 410 L/ capita-day. In refugee camps in Africa and Asia, residents may receive only 15 L/capita-day for both consumption and hygiene. For comparison, the World Health Organization defines reasonable access as the availability of at least 20 L/capita-day from a source within 1 km of the user’s dwelling (3). Although the quantity of water used varies by region, water is not distributed equally (Figure 1).