Vol. 35 – 2009 - Ecologia Mediterranea - Université d'Avignon et des ...

HANADI ISMAÏL, HUSSEIN ABOU-HAMDAN, AHMAD KOUBAYSSI, STÉPHANIE FAYOLLE, GABY KHALAF, ARLETTE CAZAUBON, JACQUES HAURY
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Study sites
The Litani River arises in the central part of
the northern Bekaa Valley at an altitude of
1050 m above sea level (asl), at a short distance
west of Baalbeck and flows between the
Lebanon Mountain to the west and the anti-
Lebanon mountains to the east, running south
and south-westerly and reaching the Mediterranean
Sea at the north of Tyres (Figure 1). It
runs 170 km long and its catchment basin is
2168 km 2 in area. Rock nature of the catchment
basin is primarily limestone and
dolomite so the river water has rather elevated
pH values. It was chosen because its morphology
and hydrological regime are typical
of most Mediterranean rivers. The floods and
the discharge are strongly dependent on the
precipitation. The low water levels occur from
June to September and there are two periods
of heavy rain and high water levels in autumn
and spring. The pollution and disturbances
Figure 1 – Map of the studied area in Bekaa region (Lebanon),
showing the location of Litani river and study sites.
occurring along the river valley are mainly
due to human activities (agriculture, urban
and industrial wastes and building activities
on the banks).
From the source to the Qaraaoun Lake (upper
Litani catchment basin), 4 stations have been
studied (L1, L2, L3 and L4) (Figure 1). In this
sector, the slope is gentle (1%). Since no ripisylve
grows on the river banks, the riverbed
receives full sunlight.
Station L1 was located at Oleik source, at an
altitude of 1.050 m asl. During wet period,
this station is present as a basin with 50 m
width. In the dry period this station is not
aquatic and is used as pasture. Station L2 is
about 950 m asl. It is located at the bridge on
the road to Rayak village. The average width
of the river bed at this point is 6 m. A road
runs along the right bank. In this area, the
river is completely dammed and polluted with
both sewage and domestic wastes; water is
brown.
Station L3 is about 900 m asl. It is located at
the main road that goes to Damascus. In this
area, the river is completely dammed. Water
is brown and garbage is present down in the
river. Station L4 is about 860 m asl and is
located in Jib Janin. The average width of the
river bed at this point is 8 m.
Material and methods
A standard sampling unit with an area of
100 m2 was used to study the macrophytic
communities (Abou Hamdan et al. 2005;
AFNOR 2003). The percentage cover of
macrophyte was evaluated by dividing the
100 m2 in each station into plots of 4 m2 . A
detailed inventory of the flora was drawn in
each plot and the percentage rate of cover of
each macrophyte taxon was assessed visually.
For this purpose, each plot was divided into
16 sub-plots 2500 cm2 in size. A value of 2%
was applied to all the species having a cover
less than 5%. To make sure that no floristic
information was lost, surveys were carried out
over a distance of 100 m (Abou-Hamdan et
al. 2005; Abou-Hamdan 2004) using the standardized
IBMR procedure (AFNOR 2003).
The following physical parameters were
determined in situ in each station: depth (with
a ruler), granulometry of the substrate (fine
= lime, silt, sands; coarse = gravels, pebbles
and boulders) (visual evaluation in%) and the
ecologia mediterranea – Vol. 35 – 2009