biological diversity and tropical forests in tunisia - PART

winter there. Waterfowl observed in January 1986 (Smeti, pere. comm.)
include:
Flamingo Teal Shoveler
Moorhen Pintail Wigeon
B. Influences
Gadwall
Mallard
Waterfowl are hunted at the lakes each year, but not at excessive
levels (about 10 hunters annually). The edge vegetation is heavily grazed
by livestock.
3.3.3. Rivers and Reservoirs
Permanect rivers ocly exist in the north, but there are intermittent
rivers acd streams scattered throughout Tunisia. All major rivers and
macy of the smaller, ictermittent rivers have at least one dam,
corstructed to conserve water for irrigation or domestic use and to reduce
flood damage. A cata~trophic~flood in 1969 eroded 260 million tons of soil
from a watershed of 8,577 km where normally 5 million tons are lost
annaally pi rant 1980). The flood also changed the watercourses of several
streams and destroyed many bridges, roads and buildings. That destructive
flood sp~rred the Tunisian government into increasing its dam constructkon
program.
Due to the dams and the long dry season, a large proportion of the
surface water evaporates before it is used for irrigation or reaches the
sea. The high ancual evaporation rate - 1400 mrn in the north to 3000 mm
in the south r rant 1980) - results in the dessication of many rivers and
some of the smaller reservoirs.
Typical vegetation along rivers and reservoirs of the north includes
planted acacia and eucalyptus and:
Tamarix sp
Carex sp
Juncus Phragmk tes communis
Nephron oleander Rubus ulrnkfolius
In southern watersheds the saline soil results in moderately halophile
vegetation. Submergent vegetation is uncommon due to the turbidity and
seasocality of waterflow kn the rivers and the depth of the reservoirs.
Tucisian rivers are poor tn fish species dkverskty (~raiem 1983).
There are only 12 species, of which 8 are native and 4 are introduced.
Fish of the northerc and central rivers and reservofrs are in the genera:
Aphianus, Gambusia, Barbus and Pseudophoximus.
Rivers provide important habitat for local populations of birds and
mammals. Although the depth and resulting lack of supmergent vegetatTon
makes most reservoirs poor habitat, several species of waterfowl and
waders ase the large freshwater bodies as migratioc rest stops. The
threateced white-headed duck uses the Besbesia dam reservoir between Tunis
acd Bizerte, and great crested grebes and some ducks breed at the Gdir el
Ghoal ponds jast outside of Tunis.