(March 2001) March 22 marks World Water Day 2001, an initiative stemming from the 1992 United Nations Conference on Environment and Development (UNCED) in Rio de Janeiro. That year, the UN General Assembly called for raising awareness about water and its threatened state on this date every year. “Water and Health” is the theme for 2001, and the World Health Organization (WHO) is the lead UN agency for the day this year.

A Limited Supply

Water is essential to human life, but its supply is finite. Though two-thirds of Earth’s surface is covered with water, only 2.5 percent is freshwater, and most of that is frozen in the polar icecaps. Altogether, less than 1 percent of all the water on the planet is available for direct human usage, and this supply is distributed unevenly around the globe. With a fixed supply of water, population growth decreases the amount available to each individual. Inefficient use may also lead to water scarcity, even in the absence of rapid population growth.

While some countries need not worry about water scarcity — Norway has 88,000 cubic meters of freshwater per person per year — others have much less freshwater and populations that are expanding rapidly. In South Asia, the average is 4,100 cubic meters of freshwater per person, while in the Middle East and North Africa the per capita level is just 1,000 cubic meters. In many countries — India and Bangladesh, for example — a large percentage of the freshwater falls as rain during a relatively short wet season (the monsoon). Because of the seasonal nature of the water supply, only about one fifth of the available water can be used in such countries.

As a general rule, countries with less than 1,700 cubic meters of freshwater per capita are termed “water stressed,” meaning that chronic and widespread shortages tend to occur. Below 1,000 cubic meters per capita, water shortages are likely to interfere with economic development and cause serious environmental damage.

Water Quality Is Crucial

Water quality is just as critical for human health as adequate supply. At present, 2.4 billion people worldwide do not have daily access to adequate sanitation facilities, according to Global Water Supply and Sanitation Assessment 2000, which was jointly produced by the WHO and UNICEF. Only 49 percent of the population in Latin America and the Caribbean has access to sewer systems, for example, while a mere 13 percent in Africa and 18 percent in Asia have access to this type of service.


Population with access to sanitation facilities*

* Examples of sanitation facilities include connections to a public sewer, connections to a septic system, pour-flush latrines, simple pit latrines, and/or ventilated improved pit latrines.
Source: WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation, Global Water Supply and Sanitation Assessment 2000 Report (2000).


The data in the graph at right suggest a massive unmet need for better sanitary facilities, particularly in Asia and Africa. However, caution should be used in interpreting these figures since the definition of “sanitation coverage” may vary from one country to another. In some African countries, a lack of sanitation coverage indicates no access to any sanitary facility. But in Latin America and the Caribbean, populations without sanitation coverage may actually have access to a sanitary facility, but one that is judged unsatisfactory by the local or national authorities. Africa’s figures in the above graph would thus be even lower if African countries had used the stricter standards employed in many Latin American countries.

The consequences of poor water quality for human health are considerable. Inadequate sanitation, faulty plumbing, and the use of human excrement as fertilizer lead to water supplies contaminated by a range of water-borne pathogens. The following examples drawn from WHO statistics illustrate the critical role that water supplies play in maintaining human health:

  • Diarrhea, which is linked to inadequate water supply and hygiene, killed an estimated 2.2 million people worldwide in 1999, according to the WHO’s World Health Report 2000. Diarrhea is the leading cause of child death around the world.
  • More than one million people die each year of malaria, a disease that flourishes in areas with stagnant water in which disease-carrying mosquitos breed.
  • Tropical water-borne diseases such as schistosomiasis affect nearly 200 million people every year — 20 million severely. Schistosomiasis in particular is caused by three types of flatworms that penetrate the skin to lay their eggs and cause damage to the bladder and liver.
  • Approximately 6 million people worldwide are blind due to trachoma, another 146 million with the disease are threatened by blindness. Trachoma tends to occur where people live in overcrowded conditions with limited access to water and health care.

The Climate Change Threat

Climate change may exacerbate existing water-related health problems, according to the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) released in February. Rising temperatures in arid regions, for example, are likely to make water scarcity an even more intractable problem in those areas. Africa, which already suffers from desertification in many places, is likely to be hit particularly hard in this respect.

There are also less obvious impacts. “Higher temperatures, heavier rainfall, and changes in climate variability will encourage insect carriers of some infectious diseases to multiply and allow them to thrive at higher altitudes,” says the IPCC report. Over the past few years, malaria cases in the highland area of Rwanda rose by 337 percent; 80 percent have been attributed to changes in temperature and rainfall that create a better breeding environment for mosquitoes that carry malaria. While it is difficult to make precise projections, the report anticipates a significant increase in the number of people exposed to mosquito-borne diseases such as dengue and malaria, each of which potentially affects 40 percent to 50 percent of the world population. (Dengue is an infection that may cause dengue fever, a severe flu-like illness, and dengue hemorrhagic fever, a potentially lethal complication that is the leading cause of childhood death in several Asian countries.)

The IPCC report also notes that climate change may make floods more frequent, which could lead to increasing rates of cholera. During the 1997–1998 El Nino, excessive flooding caused cholera epidemics in Djibouti, Somalia, Kenya, Tanzania, and Mozambique. Poor countries are most vulnerable to the health impacts of flooding since actual disease occurrence is heavily influenced by other factors such as local environmental conditions, socioeconomic circumstances, and the public health infrastructure.

Better understanding of the growing need for adequate and safe water supplies is critical for protecting human health worldwide. To raise awareness about these issues, the WHO and the IRC International Water and Sanitation Center have launched a website to commemorate World Water Day 2001. The site includes an advocacy guide, disease fact sheets, theme articles, and case studies of success stories. There are also numerous links to resources on water supply, water quality and treatment, health and hygiene promotion, and sanitation. The website also describes events that are planned for World Water Day 2001 to emphasize the crucial connection between water and health.


Bingham Kennedy, Jr. is associate editor and Liz Creel is population specialist, at the Population Reference Bureau.


For More Information

World Water Day 2001 website: www.worldwater.org.

For the IPCC Third Assessment Report, go to the IPCC website: www.ipcc.ch.

To view the Global Water Supply and Sanitation Assessment 2000 online, visit www.who.int/docstore/water_sanitation_health/Globassessment/GlobalTOC.htm on the WHO website.