Africa Water Atlas - UNEP/GRID-Sioux Falls

Figure 2.12.8: Years of drought and the construction of two dams brought
the Djoudj and Diawling wetlands to a low point in the 1980s. After changes
in artificial impoundments and water flows, the wetlands rebounded
Djoudj and Diawling Wetlands
Prior to construction of the Diama and Manantali dams, dry season
tides could be detected up to 470 km upstream of the ocean
bringing salt water influence up to 300 km inland of the Senegal
River mouth (Isupova and Mikhailov 2008). Then, in August of each
year during the Senegal River’s peak flow, floods would flush much
of the delta with freshwater from the annual monsoons (Duvail
and Hamerlynck 2003). The alternating brackish and freshwater
environment created a unique wetland system that supported
rich natural habitats and traditional livelihoods including fishing,
grazing, agriculture, and the production of artisanal mat-making
(Duvail and Hamerlynck 2003, Fall and others 2003). Natural
habitats thrived throughout history under this hydrological
regime, including mangroves, saltmarshes, lagoons, acacia
woodlands, and floodplain grasses (Fall and others 2003, WMO
2004, Isupova and Mikhailov 2008).
In Figure 2.12.8, the 1984 satellite image of the Diawling and
Djoudj area shows the wetlands in decline under the influence
of the 1970s and 1980s droughts, which also created a food crisis.
The Senegal Basin countries in response to this crisis proposed
to develop intensive-irrigated rice production by building two
dams on the river. The dams, completed in 1985 and 1988, were
to facilitate development of irrigated agriculture, hydropower
and river transport, although irrigation in the delta has been
less widespread and less productive than planned (Duvail and
Hamerlynck 2003, Poussin and Boivin 2002, OMVS n.d., FAO 1997).
The dams also change the delta’s natural hydrological
patterns with several negative impacts on the natural environment
and the local communities that relied on their ecosystem products
and services (Duvail and Hamerlynck 2003). In the area of Diawling,
fish stocks decreased and much of the wetland vegetation
disappeared (Bâ Amadou 2004). Upstream of Diama Dam, the
change to an all-freshwater regime led to invasive plant species
overtaking much of the natural vegetation (Mietton and others
2007). Invasive species posed such a threat that UNESCO listed
Djoudj on its List of World Heritage in Danger (UNESCO n.d).
Beginning in the early 1990s, changes in the hydraulic
infrastructure and dam management allowed controlled water
releases to better mimic previously existing conditions (Duvail
and Hamerlynck 2003b). The wetlands in the Diawling area have
substantially recovered. While invasive species in Djoudj continue
to be a concern, UNESCO removed Djoudj National Park from
its List of World Heritage in Danger in 2006 following mitigation
efforts that include biological controls. In the 2009 image, the
wetlands on both sides of the river are lush with vegetation
following changes in the dams and their operation and a period of
improved rainfall.
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