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, 
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