Agriculture Reference
In-Depth Information
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cal Convergence Zone (ITCZ), subtropical anticyclones, monsoonal wind
systems, tropical cyclones, easterly/westerly wave perturbations, subtrop-
ical jet streams, East African low-level jet stream, extratropical weather
systems, teleconnection with El Niño/Southern Oscillation (ENSO), and
quasi-biennial oscillation (Ogallo, 1988, 1991, 1994). In addition, com-
plex physical features such as large inland lakes, mountains, and complex
orographic patterns (e.g., the Great Rift Valley) influence rainfall patterns.
Lake Victoria in western Kenya is also one of the largest freshwater lakes
in the world and has its own strong circulation patterns in space and time.
These regional features often induce complex patterns of rainfall anoma-
lies over the region and reduce the chances of extreme positive/negative
anomalies occurring across the country.
Figure 18.2 shows that the larger amount of mean annual rainfall is
concentrated over the mountain slopes and near the large bodies of water.
More than 80% of Kenya may be classified as arid or semiarid lands
(ASALs) with annual rainfall less than 700 mm (figure 18.3).
The arid land classification is based on the moisture index (Pratt et al.,
1966), which ranges from
[239
Line
——
0.0
——
Norm
PgEn
−
50 to
−
60 for very arid, from
−
40 to
−
50
for arid, and from
40 for semiarid land categories. Interannual
rainfall fluctuations are common in all locations, but the highest variabil-
ity is concentrated within the ASALs. Most of the annual rainfall is re-
ceived during the two separate rainfall seasons (i.e., the March-May and
October-December periods), with higher rainfall being in the first season.
Agricultural practices are therefore tied to the seasonal nature of rainfall.
Rainfall in many parts of Kenya is often skewed, and at times a large pro-
portion of it falls early, even before the crop has been planted. Such rainfall
is ineffective, being of little use to the young plants, which have underde-
veloped root systems. Some locations to the west, however, receive a third
rainfall peak during July-August, and some locations near the large bodies
of water receive substantial rainfall throughout the year (figure 18.2).
Though floods occurred during 1997-98 (often attributed to El Ni no),
one of the longest and severest droughts in Kenya's history occurred from
mid-1998 through 2001. The drought had harsh negative impacts on agri-
culture and livestock (figure 18.4), wildlife, tourism, water resources, and
hydroelectric power generation.
The low water levels in the dams led to strict power rationing, which
resulted in large losses to the economies. Water supplies for industrial and
domestic consumption were not spared by the drought. There were serious
water shortages both in urban and the rural areas. Lack of water and
pasture led to severe conflicts between wildlife and pastoral communities.
Similarly, lack of adequate power due to prolonged drought resulted in
loss of employment and economic hardships. The government had to seek
support from the international community to address the impacts.
Sometimes human practices contribute to droughts. For example, some
farmers in the semiarid Laikipia district and Wakambas of East Province
have introduced maize (a higher water-demanding crop) to replace a mark-
−
30 to
−
[239
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