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The area offers the attraction of a variety of physiographic soil units, which is
one of the reasons it was chosen initially by ITC. The main landforms found
(fig. 2 ) in the area are:
1. Alluvial valleys (A), mainly along the Guadiana river, which flows approxi
mately through the centre and serves as the main drainage channel for the
whole survey area. Some tributary valleys have been delineated separately.
2. Gently undulating to rolling landforms, in which three categories could be
distinguished:
a) Areas (R) characterized by an abundance of more or less rounded pebbles,
with a diameter from 3-18 cm, inbedded in the soil matrix. These areas
are presumed to be the result of a past braiding river activity.
b) Areas (K) characterized by a coarse sandy top soil with an arkose substratum
and
c) Areas (M) characterized by heavy clay soils with a depth varying between
0.25 m to several metres usually containing a calcic horizon. The parent
material dates from the Miocene Period.
d) Areas (C) of low hills and colluvial valleys, characterized by medium tex
tured soils. These areas are situated between the areas of higher hills and
mountains (see below).
e) Hills and mountains. They are formed by a variety of metamorphic and ig
neous rocks varying from schists, quartzites to granites and diorites. Some
of the lower hills and colluvial valleys in between are cultivated (landform
(C), see above), the rest are used for pasture if at all.
The most important units from the point of view of agricultural economy of the
region are the alluvial and the miocene clay areas. The climate of the region is
typical Mediterranean with dry hot summers and moderate winters with an
average precipitation between 450 - 500 mm per year.
2. OUTLINE OF STUDY
2.1 General
Imagery was only taken on a few occasions of the test site area by the ERTS -1
satellite, on the 29th September 1972 and 9th March 1973. The imagery of Sep
tember 5th and November 16th 1973 could not be used as it did not become
available in time for the present study. Unfortunately, during the passage of the
satellite on 29th September 1972 the area had a cloud coverage of about 50%. So
the imagery taken, although of good quality from the technical point of view, was
not useful for interpretation purposes. Practically all efforts were concentrated
on the imagery of the 9th March 1973, which was cloud free. Moreover stereoscopy
was precluded because the adjacent run was affected by cloud cover.