80 r
CLEAR RIVER WATER
TURBID RIVER WATER
VEGETATION
SILTY CLAY SOIL
MUCK SOIL
Figure 3. A rain-fed and sparsely planted maize field in
Somalia in the GU - Season.
Figure 2. Spectral reflectance of various earth surface
features (Hoffer, Lindenlaub 1976).
spectral reflectances are strongly influenced by the surrou
nding soil.
3 LIVESTOCK MONITORING
The role of livestock sector for the national economy in
many of the drought affected countries is enormously
important. In Somalia, for example, livestock production
provides over 50 percent of the gross domestic product and
around 80 percent of the export earnings.
The application of remote sensing to livestock monitori
ng was mainly confined to the census of the animal
population. The method used was mainly aerial photography
with small cameras mounted on low-flying light aircraft,
and a simultaneous counting from plane, combined with an
eventual field check. A wide experience has been collected
in the wildlife monitoring in Eastern Africa (Gwynne,
Croze 1980).
In view of the ecological deterioration, which is a
dynamic process, it has been realized that it is essential to
monitor the rate of change in the pastureland or the
rangeland to take necessary precautions. The causes of this
ecological deterioration are due to the increase of animal
population, the irregularity or the absence of rainfall, and
the abuse of the renewable resources such as the
deforestation processes. Rangeland monitoring today is
winning a great deal of attention in many countries, where
livestock rearing plays a dominant role in the rural
population. Some of the variables that are needed here are
the vegetation or grass distribution, the available water
resources, both surface and underground, and the animal
and human influence in the rangelands. Due to the fact
that multitemporal data of the environmental imagery is
available, the ecological monitoring with this relatively
new source of data is increasing. Several studies such as
(Tucker,Hielkma,Roffey 1985) were made, investigating
the potential of satellite remote sensing for ecological
monitoring using LANDSAT and NOAA data. The results
were quite promising.
4 DROUGHT MONITORING
In order to obtain information on the regions susceptible to
drought emergencies, it is necessary to set up a mechanism
for collecting an immediate and reliable data on the
irregularities in climate such as the delay or the absence of
the seasonal rainfall so as to mobilize appropriate
measures. These measures are being carried out at various
levels, namely, the international, regional, and national.
Some of these activities, in which remote sensing is used
will be described briefly.
4.1 International
The international drought monitoring programmes have the
advantage that the world public could be effectively
informed.
The FAO has, for example, established a global
information and early warning system to provide prior
notice of the potential food shortages in many developing
countries, particularly in the African countries, that are
imminent to drought emergencies. Information derived
from satellite imagery is today an essential complement to
the information supplied by the FAO representatives based
on field information, and the concerned countries. The
main activities of FAO in drought monitoring programmes
by means of satellite remote sensing cover two parts
(Kalensky 1984):
- The estimation of precipitation from METEOSAT
images (fig. 4).
- The monitoring of vegetation greenness based on
NOAA/AVHRR data.
The FAO in cooperation with NASA is setting up a drought
monitoring programme by means of the NOAA/AVHRR
vegetation index data. Colour composite images processed
at NASA are delivered to the FAO for interpretation. It is
reported that relatively good results were obtained.
The United States Agency for International Development
(USAID) in cooperation with NOAA/NESDIS is conducting a
three year pilot project on "Climate Impact Assessment"
for the Sahel Countries, including Ethiopia and Somalia.
The main objective of this project is to increase the
capability of these countries in providing information on
the probable crop failures and the subsequent food crises.
The input for this programme are, among others, the
rainfall analysis and the vegetation condition based on
NOAA/AVHRR imagery. A monthly assessment is made for
each country .
The United Nations Environmental Programme (UNEP)
has installed a Global Monitoring System (GEMS). Though
this system has a global character, particular regional
problems such as the drought monitoring in Africa are
given an important attention. The activities here comprise
the observation in the variation of climate, soil, flora and
fauna, and influence of human beings in the region. Apart
from the governmental and none-governmental reports,
GEMS retrieves its information input from satellite
imagery and aerial photography in combination with ground
surveys for statistical sampling and verification purposes.
4.2 Regional
Realizing that the causes and effects of the recurrent
droughts are not only confined to the national boundaries, a
set of regional intergovernmental organizations emerged
since the first drought in 1973/74. The latest organization
that has been founded is the Intergovernmental Authority
on Drought and Development (IGADD) in Eastern Africa,
whose headquarters will be in Djibouti. The aims of this
organization are among others the urging of the member
states to allocate a major part of the national resources to
emergency programmes for drought stricken areas and
combat the causes of drought and desertification using the
existing information and technology. The Regional Remote
Sensing Centres in Nairobi and Ougadougu could be of
great value in training the staff of the member countries
and participating in the research and application projects,
459
