The primary resource management problem in Sub-Saharan Africa (the Sahel) is increasing aridity or desertification. Space observations of sand streams, dune orientations, moisture and vegetation changes and other factors associated with desertification have been made. A second major interest is grazing of cattle, sheep and goats which is associated with major movements of people and animals twice yearly to obtain forage. The changes in available forage are being observed. The location of the cultivators is also being mapped from ERTS imagery. Hydrological analysis is being carried on in the Niger and Bani river watersheds. So far, good imagery of the maximum flood stage has been obtained and assessed

Macleod, N. H.

English

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Paper R 5 
APPLICATIONS OF REMOTE SENSING (ERTS) TO RESOURCE MANAGE- 
MENT AND DEVELOPMENT IN SAHELIEN AFRICA (REPUBLtC OF MALI) 
N. H. MacLeod, Department of Biology, The American University, Washington, 
D. C. 
ABSTRACT 
The primary resource management problem in 
Sub-Saharan fifrica (the Sahel) is increasing 
aridity or desertification. Space observations 
of sand streams, dune orientations, moisture and 
vegetation changes and other factors associated 
with desertification have beenhnade. It is not 
yet known whether the process is caused by human 
activities or climatic changes or both. 
sheep and goats which is associated with major 
movements of people and animals twice yearly to 
obtain forage -- from the savannah in fall and 
winter, and from huge areas of marsh (the 
Inland Delta) in spring and summer. These move- 
ments (transhumance) pass through more settled 
cultivators and into regions occupied by fisher- 
men. The changes in available forage are being 
observed. The location of the cultivators is 
also being mapped from ERTS imagery -- for the 
first time. Field burning after rains is widely 
practiced and has been observed and the extent 
measured in ERTS imagery. 
this measurement is an estimate o f  area to be 
planted to grain in the next season -- an un- 
measured parameter heretofore. 
Hydrological analysis is being carried on in 
the Niger and Bani River watersheds. 
timing and areal extent of the annual flood is 
of particular interest. So far, good imagery 
of the maximum flood stage has been obtained and 
assessed. 
Geologic information on fault zones, sand 
dune formations, scarps, tectonic basins and 
focal points of faulting (points from which 
fractures appear to radiate) are all visible and 
heretofore mapped inaccurately or not at all. 
The information on possible areas in which 
A second major interest is grazing of cattle, 
In some areas of Mali, 
The size, 
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https://ntrs.nasa.gov/search.jsp?R=19730019631 2020-03-17T08:50:29+00:00Z
minera l iza t ion  has occurred are being mapped 
and noted f o r  Malien o f f i c i a l s  car ry ing  on t h e i r  
own ERTS inves t iga t ions .  
A t  t h e  present  t i m e ,  t h e  count r ies  i n  t h e  semi-arid zone of West 
Afr ica  -- t h e  Sahelien Zone -- are faced not  only with t h e  problems of 
economic development, but a l s o  with ecologic  d e t e r i o r a t i o n  which they 
perceive t o  be a major and rap id ly  i n t e n s i f y i n g  hazard. 
The Republic of Mali i n  West Afr ica  has recognized t h e  problems of 
economic development and has a l s o  recognized t h a t  t h e  d a t a  base of fund 
of knowledge concerning t h e i r  n a t u r a l  resources  i s  very  meager. 
Maliens a l s o  recognize t h a t  t h e  productive p o t e n t i a l  of t h e  Sahel ien 
Zone may br ing t h e i r  economy t o  a p o s i t i o n  of a major g r a i n  and live- 
s t o c k  producer i f  they can cont ro l  d e s e r t i f i c a t i o n  and combine hydro- 
l o g i c  and agronomic resources.  
i n t o  world markets w i l l  be hastened by t h e  discovery and devexopment of 
mineral  o res ,  energy sources (including geothermal), ground f o r  crop and 
l i v e s t o c k  production, water, and petroleum resources.  Further ,  they 
r e a l i z e  t h e i r  t echnica l  se rv ices ,  though s t a f f e d  with a b l e  people, are 
inadequate f o r  t h e  performance of t h e  necessary miracles. 
They a l s o  recognize t h a t  t h e i r  e n t r y  
M r .  Mamadou Konate, Director ,  Geological and Mining Services  of 
Mali, i n  conjunction with U.S.  AID,  USGS and,NASq technicians and mem- 
b e r s  of t h e  Malien t e c h n i c a l  se rv ices ,  i s  P r i n c i p a l  I n v e s t i g a t o r  of a n  
ERTS-1 i n v e s t i g a t i o n  through which t h e  government of Mali (GOM) hopes t o  
e s t a b l i s h  t h e  necessary d a t a  base o r  resource inventory f o r  long-range 
development planning i n  geology, hydrology, f o r e s t r y ,  a g r i c u l t u r e  and 
grassland management. (I a m  speaking today both as a co-invest igator  i n  
t h e  GOM study and as a P r i n c i p a l  Inves t iga tor  f o r  t h e  U.S. "counterpart" 
ERTS inves t iga t ion  -- UN431). I have j u s t  re turned from M a l i ,  and I 
have the  following repor t  on our progress i n  a n a l y s i s  of t h e  ERTS-1 
imagery i n  r e l a t i o n  t o  Malien development goals.  
F i r s t ,  progress i s  being made i n  developing a d e t a i l e d  geologic map 
of t h e  country (Figure 1). Overlays of geologic f e a t u r e s  drawn from t h e  
imagery of t h e  Gao region are compared with recent  maps drawn from French 
f i e l d  s tud ies .  
l ines ;  more s p e c i f i c  de l inea t ion  of sand f i e l d s ;  and mapping of sedi-  
mentary pediments i n  t h e  area.  
follows lineaments apparent ly  cont ro l led  by these.  The Gao graben (a 
downfaulted block) i s  a f e a t u r e  of major i n t e r e s t  because o f . i t s  
p o t e n t i a l  as z petroleum o r  water source. 
graben has  now been q u i t e  prec ise ly  mapped from t h e  space imagery. 
The major addi t ions  from the  ERTS imagery are f a u l t  
The Niger River, i n  t h i s  and o ther  areas, 
The  western boundary of t h e  
I n  t h e  next sets of f i g u r e s  of t h e  southern Inland Delta of t h e  
Niger River -- a tec tonic  basin (Figure 2) ,  and t h e  frame to  t h e  w e s t ,  
which contains  a major i r r i g a t i o n  scheme i n s t a l l e d  by t h e  French (a l so  
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a tec tonic  basin),  and the  so-called Delta Mort o r  Dead Delta 0- w e  can 
point out some major advances i n  understanding of the  hydrologic and 
vegetation regimes. 
courses which are similar i n  or ien ta t ion  t o  the  major lineaments -= 
These lineaments 
have been described i n  the  Bandiagara Highland t o  the  east, but not i n  
the  lowlands, We had thought the  arrow-shaped, l ight-colored s t ruc tu res  
were dunes. 
with a ground observation a t  Mopti ( located a t  the  arrow i n  Figure 2), 
showed these were barren f l a t s  -- ac tua l ly  l a te r i te  covered by less 
than a meter of sand. These f l a t s  are cu l t iva ted  i n  aome.villages. 
They are flooded each year and are thus supplied with water. Millet, 
rice, and cotton are the  major l oca l  crops. 
ments has an in t e re s t ing  re la t ionship  t o  ground water supplies i n  the  
region -- a resource which the  Maliens wish t o  develop f o r  l ives tock  
production. In  years of below-normal prec ip i ta t ion ,  the  flow of water 
out  of the  Inland Delta i s  g res t e r  than can be accounted f o r  by pre- 
c i p i t a t i o n  alone. 
question is where i s  t h a t  reservoir  of ground water? We f e e l  t ha t  t he  
f r ac tu res  may be e i the r  the  reservoi rs  themselves, o r  t h a t  they act as 
channels fo r  the  aquafers supplying the  ex t r a  outflow. 
can be ra ther  inexpensively tes ted  by d r i l l i n g  i n t o  t h e  lineaments. 
t i ons  associated with the  north and south advance and retreat of t he  
In t e r t rop ica l  Convergence (ITC) each summer. 
about six months t o  flow downstream. On 22 September 1972, the  date of 
t h i s  image, the flood c r e s t  was i n  the  southern Inland Delta, shown here, 
and thus i t s  a e r i a l  extent  can be measured from t h i s  image. This is an 
important measurement f o r  nomadic animal husbandrymen who bring t h e i r  
catt le in to  the Delta each year t o  forage, f o r  t h e  Bozo fishermeh who 
harvest  50,600 tons of f i s h  from t h e  Niger each year,  and, of course, 
f o r  the  cu l t i va to r s  i n  the  Delta. 
We f ind  tha t  the Niger and Bani Rivers follow 
, possibly f r ac tu res  found throughout southern Mali. 
They have been mapped as such -- dunes which are thought 
, t o  be several thousand years old.  An aerial reconnaissance, coupled 
The presence of the  l inea-  
The excess outflow must come ,from ground water. The 
These hypotheses 
The Niger River floods each year as it c a r r i e s  off the precipi ta-  
The flood crest takes 
The question of dese r t i f i ca t ion  can a l s o  be examined i n  t h i s  image. 
The soil is  sacdy i n  most of the  area, but one would l i k e  t o  examine 
what appear as deposi ts  of dunes o r  regions of sand t o  determine the  
mode and time of t h e i r  or igin.  
t ha t  between the Niger and Bani Rivers where an unwatered r i v e r  channel 
can be seen. There is no vegetation or  water i n  the  channel -- i t  is 
not  a wadi o r  channel f o r  an ephemeral r i ve r ,  f o r  i t  would be watered 
a t  t h i s  time of peak runoff i f  it were. 
the  stream was not previously mapped. 
increased a r i d i t y ,  o r  has the watershed been captured by the  Bani o r  
Niger Rivers? Why is  there  no vegetation? 
tence of t h i s  and other  such unwatered drainage systems i n  southern Mali 
pose major hydrologic problems worthy of much fu r the r  study. 
One pa r t i cu la r ly  in t r igu ing  area is 
No one knows the  answers, but 
Is there  no water because of 
The discovery of the exis- 
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In the northwest corner of the image, one can see a cuspid pattern 
of tones. 
people. The different tones are caused by differences in the type of 
vegetative cover -- the darker tones correlating with scattered trees 
and shrubs, the lighter with open grassland. Color additive techniques 
can be used on successive images to determine the cahnges in available 
forage during the rain-free season and the zones of highest productivity. 
This is an area of range for the Peul, a cattle-owning 
In Figure 3 the irrigation scheme, Office du Niger, is a prominent 
feature. 
channels, irrigated fields, and the adjacent cultivator fields. We 
have also mapped temporal changes in vegetative cover and soil moisture 
in the region. 
By digital analysis we have mapped the pattern of irrigation 
Surface runoff patterns are peculiar in the region west of the 
irrigation scheme. 
drainage-ways. 
case. 
some hope of finding aquafers shallow enough to be developed for live- 
stock water-points so that the range may be better utilized by nomadic 
cattlemen. 
In the imagery we find some areas devoid of surface 
Aerial reconnaissance showed us that this is indeed the 
We feel that soils are very porous in the area and that there is 
We were particularly pleased to find the lineaments trending 
northeast and northwest from the northern part of the Office du Niger. 
By bringing together our data resources, we found that the northwest 
lineament (which has a water-formed channel in it) leads to a large 
circular depression -- the Hodh -- on the Mali-Mauretanian border. 
1964 the depression was so filled with water that it became a lake -- 
even now there is surface water detectable in the imagery. 
one knew the source of the lake water -- it was a "gift of God." 
was, but we have found the channel -- that to the northwest of the 
Office du Niger. 
trolling water flow into the Office du Niger from the Niger River during 
the Niger flood. 
In 
However, no 
So it 
It can be filled using existing structures by con- 
A dry-bed stream channel is located in the west-central portion of 
the image. 
channel, which continues northward to the Hodh and beyond. In the Hodh 
region of the channel is more than two miles wide and is located in the 
Sahara Desert itself. Further studies must be carried on; but the 
stream beds, the lake bed, and the lineaments make an intriguing com- 
bination for one interested in mapping and developing surface and ground 
water resources in that region. 
Obviously, a large flow of water was required to form the 
All of the Mali images are full of interest for many disciplines. 
We have not fully addressed the question of desertification, but the 
ability to map sand from the imagery has been demonstrated. We also are 
able to map much of the vegetation of Mali to set a baseline condition 
for further development of extensive, intensive, and irrigated 
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agr icu l ture ,  
There a re  s t i l l  fasc ina t ing  questions remaining concerning t h e  
lineaments, some of which control  the  course of the  Niger, the  Bani, 
t he  shape of the  Delta and the  Office du Niger, and re la t ionship  of t he  
lineament t o  the former drainage channels. 
now t h a t  a data base is becoming ava i lab le  t o  reveal  t he  na ture  of the  
land surface. 
The answers can be sought 
While these comments merely brush l i g h t l y  over the  concerns of 
development, merely s t a t i n g  some of the  discoveries  without f u l l y  eon- 
s ider ing  t h e i r  implications f o r  improvement and without conveying a l l  
t h a t  has been done i n  analysis ,  one may surmise t h a t  a t  least the  in- 
ventory of resources has begun. 
a f fec ted  the planning processes of t he  Malien government and of aid- 
donor agencies. We are a l so  acquiring au appreciation of the  dynamics 
of t he  cultivator-nomad relat ionships ,  t he  cl imate  and land-use, and a 
more quant i ta t ive  approach t o  the dese r t i f i ca t ion  problem. 
J u s t  t h i s  beginning has a l ready 
A fur ther  immediate outcome is the  emerging understanding by a l l  
par t ic ipa tns  i n  the  pro jec t  -- Malien and U.S. ’-- of the  regional  
nature  of problems confronting Maliens i n  evolving a new kind of 
economy and the interwoven f ab r i c  of her na tura l  resources -- geologic, 
hydrologic, b io t i c ,  and human -- t h a t  can.be mustered f o r  t he  develop- 
men t . 
ew 
Figure 1 Republic of Mali 
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Applications of remote sensing (ERTS) to resource management and development in Sahelien Africa (Republic of Mali)

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