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Drought
Drought
is a condition of moisture deficit sufficient to have an adverse effect
on vegetation, animals, and man over a sizeable area
A
drought is defined as "a period of abnormally dry weather
sufficiently prolonged for the lack of water to cause serious hydrologic
imbalance in the affected area." -Glossary of Meteorology
(1959).
In
easier to understand terms, a drought is a period of unusually persistent
dry weather that persists long enough to cause serious problems such as
crop damage and/or water supply shortages. The severity of the drought
depends upon the degree of moisture deficiency, the duration, and the
size of the affected area.
There are actually four different
ways that drought can be defined.
-
Meteorological-a
measure of departure of precipitation from normal. Due to climatic
differences, what might be considered a drought in one location of the
country may not be a drought in another location.
-
Agricultural-refers
to a situation where the amount of moisture in the soil no longer meets the
needs of a particular crop. This condition can arise, even in times of
average precipitation, owing to soil conditions or agricultural techniques.
-
Hydrological-is
brought about when the water reserves available in sources such as aquifers,
lakes, and reservoirs falls below the statistical average. This condition
can arise, even in times of average (or above average) precipitation, when
increased usage of water diminishes the reserves.
-
Socioeconomic-refers
to the situation that occurs when physical water shortages begin to affect
people.
While
much of the weather that we experience is brief and short-lived, drought
is a more gradual phenomenon, slowly taking hold of an area and
tightening its grip with time. In severe cases, drought can last for
many years, and can have devastating effects on agriculture and water
supplies.
According
to United Nations estimates, one third of the world's population lives
in areas with water shortages and 1.1 billion people lack access to safe
drinking water and 2.6 billion people are without adequate water for
sanitation. Consequently disease and significant deaths arise from
people using contaminated water supplies; these effects are particularly
pronounced for children in underdeveloped countries, where 3900 children
per day die of diarrhea alone
Climate change has also provoked more frequent and
intense droughts in sub-tropical areas of Asia and Africa, exacerbating
shortages in some of the world's poorest countries. According to a UN
climate report, the Himalayan glaciers that are the sources of Asia's
biggest rivers - Ganges, Indus, Brahmaputra, Yangtze, Mekong, Salween
and Yellow - could disappear by 2035 as temperatures rise.
While
the world's population tripled in the 20th century, the use of renewable
water resources has grown six-fold. Within the next fifty years, the
world population will increase by another 40 to 50 %. This population
growth - coupled with industrialization and urbanization - will result
in an increasing demand for water and will have serious consequences on
the environment.
World
Water Shortage
Projected
Water Scarcity in 2025
By
2025, 1.8 billion people will live in countries or regions with absolute water
scarcity. Most countries in the Middle East and North Africa can be classified
as having absolute water scarcity today. By 2025, these countries will be joined
by Pakistan, South Africa, and large parts of India and China. This means that
they will not have sufficient water resources to maintain their current level of
per capita food production from irrigated agriculture—even at high levels of
irrigation efficiency—and also to meet reasonable water needs for domestic,
industrial, and environmental purposes. To sustain their needs, water will have
to be transferred out of agriculture into other sectors, making these countries
or regions increasingly dependent on imported food.
Many
African countries, with a population of nearly 200 million people, are facing
serious water shortages. By the year 2025, it is estimated that nearly 230
million Africans will be facing water scarcity, and 460 million will live in
water-stressed countries
Credit: NOAA, The National
Weather Service, The United Nations, National Drought Mitigation Center
University of Nebraska-Lincoln
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