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World Water Day 2001: Floods and droughts


  Table of contents
  • Too little—or too much—water is the cause of most of the natural disasters
  • Climate change is increasing the risk of water disasters
  • Water disasters affect health in several ways: increased infection, malnutrition, psychological trauma, polluted water sources
  • Every country needs to plan for water disasters
  • International cooperation and shared policies, such as in river basin management, can reduce the effects of disasters

When does a shortage—or excess—of water become a disaster rather than a temporary inconvenience? The answer may be obvious in prolonged drought or widespread flooding, but not so clear-cut in communities already at health risk from poverty, poor sanitation and limited coordination of health care and other services. Such communities may be unable to restore normality after a water emergency.

Water disasters can be sudden, as in flooding, or progressive and long lasting, as in drought. This affects both the way the disaster is identified and managed, and the timescale of the health effects. The health effects can be classified as:

  • immediate, for example drowning or injuries during flooding;
  • intermediate, such as progressive food shortage or epidemics following a flooding;
  • and long term, such as epidemics and severe lack of food and drinkable water.

The long-term health effects of water disasters are usually due to the lack of prompt restoration of public health services and interventions, with the resulting risk of epidemics and other ill health. The health effects of climate phenomena such as the El Niño Southern Oscillation (ENSO) also tend to develop gradually. The recent ENSO during 1997-8 was particularly severe in its effects: the associated natural disasters affected an estimated 160 million people (WHO, 1999). The slow time scale of droughts means that ill health may not be identified until the drought has persisted for months, affecting food supplies as well as the water needed to maintain health.

Whether a water emergency turns into a disaster depends on whether the community can take effective measures without external assistance. One working definition of a disaster is that it causes at least 10 deaths or results in an appeal for outside assistance (WHO 1999). Whatever the definition, disasters involving water are increasing. In recent decades there has been an increase in the numbers of deaths and the numbers of people affected by weather disasters such as droughts and floods (WHO 1999). Climate change appears to be responsible for at least some of this increase: and while global warming has been acknowledged, the term is misleading because it leaves out the key element of water. Floods are the second most frequent cause of natural disaster, after windstorms. The largest cause of deaths through natural disaster is drought, because of the associated severe food insecurity: examples include the high death rate in Sahelian people in Africa in the early 1970s and mid-1980s - and droughts are not only increasing, but also lasting longer.

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