Agriculture Reference
In-Depth Information
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
a brief description of drought definitions that have been adopted in some
countries.
Despite the variation in drought definitions, a drought is broadly cate-
gorized as meteorological, hydrological, agricultural, or socioeconomic. A
meteorological drought is said to occur when seasonal or annual precipi-
tation falls below its long-term average. A hydrological drought develops
when the meteorological drought is prolonged and causes shortage of sur-
face and groundwater in the region. An agricultural drought sets in due
to soil moisture stress that leads to significant decline in crop yields (pro-
duction per unit area), and a socioeconomic drought is a manifestation
of continued drought of severe intensity that shatters the economy and
sociopolitical situation in a region or country.
Meteorological drought is just an indicator of deficiency in precipita-
tion, whereas hydrological and agricultural droughts are physical man-
ifestations of meteorological drought. This topic focuses on agricultural
drought, which is the most complex category of drought. One can detect a
hydrological drought by observing water levels in ponds, reservoirs, lakes,
and rivers. However, such an instantaneous observation is not possible in
the case of agricultural drought. Unlike a hydrological drought, an agri-
cultural drought occurs over a large area, and its impact is not accurately
assessed until after crops are harvested—a few months after the symptoms
of agricultural drought begin to appear. The symptoms may be deficiency in
precipitation, failure of rains/monsoon systems, and poor crop conditions.
Precipitation is one of several components of the hydrological cycle that
is driven by atmospheric and oceanic circulations, together with gravity
(Yevjevich et al., 1978). At times, the cycle experiences an abnormal change
in its pattern due to changes in the patterns of atmospheric and ocean
circulations. Such an atmospheric activity is called El Niño and Southern
Oscillation (ENSO). Chapter 3 describes how this activity is linked to the
occurrence of agricultural droughts
.
An agricultural drought at a global
scale can cause severe food shortage or even famine in some countries,
causing loss of both the human and livestock population. Chapters 21 and
22 focus on methods to help move livestock to greener pastures at times of
droughts in Africa.
[4],
Line
——
-0.1
——
Shor
PgEn
[4],
M
onitoring and Predicting Agricultural Drought
Effective and timely monitoring of agricultural droughts can help develop
an early warning system which, in turn, can minimize losses due to
droughts. International organizations such as the World Meteorological
Organization (WMO), the Food and Agriculture Organization (FAO), and
the United Nations Environment Program (UNEP) keep a watch on the de-
velopment of agricultural droughts and famines in the world. Chapters 31,
32, and 33 elaborate on operations of WMO, FAO, and UNEP, respec-
tively. In addition, the Famine Early Warning System (FEWS; chapter 19),
Search WWH ::
Custom Search