Management of a Tropical River: Impacts on the Resilience of the Senegal River Estuary - The Land/Ocean Interactions in the Coastal Zone of West and Central Africa - page 43

Fig. 3 Senegal River flows at
Diama dam station (1986-2010)
(OMVS Data) Organisation pour
la Mise en Valeur du Fleuve
Sénégal: Organization for the
Development of the Senegal
River

Fig. 4 Changes in water level at
the Saint-Louis Station
(1964-2012) (Data source:
Division Régionale de
l'Hydraulique de Saint-Louis/
Ministère de l'Hydraulique et de
l'Assainissement)

300

250

200

150

100

50

0

years

(Fig. 3 ) enable determination of the estuary's monthly and
annual flows, showing two periods:
• a 4-month period (August to November) during which the
estuary is invaded by flooding water and
• a 8-month period during which the estuary is subject to
marine influence.
The dam's highest water flow is in October. The highest
flows are in August, September, October, and November,
and the lowest usually in December, January, February,
March, May, April, June, and July.
In order to ensure that instructions on the dam's proper
management are followed, occasional releases can be car-
ried out by managers to guarantee its safety. The openings
of floodgates are related to the support of raising water
levels at the Manantali dam, which at certain times requires
substantial water releases to be taken from reserves inten-
ded for other needs, while higher than turbine output (Bader
1997 ). Moreover, with the operation of the hydroelectric
station at the Manantali Dam since 2002, the floodgates of
the Diama Dam are regularly opened to avoid overflow of
the river banks.

Figure 4 shows changes in water level at the Saint-Louis
station from May 1964 to April 2012, showing a succession
of peaks which reflects the strong inter-annual variability of
the flow. Water flows have reduced since the 1970s with a
clear decline in water level, from a peak of 281 cm in
1965-1966 to an average of 54 cm in 1972-1973 reflecting
changes in the climatic conditions in the Senegal River basin.
Although insignificant, the river's water level seems to have
experienced a slight increase in recent years, with an average
of 129 cm in the 1992-1993 period. As a whole, there is a
gradual fall from 1964 to 1971 and since about 1997.
The monthly water levels at the Saint-Louis station vary
according to the totals discharged by the dam. They reach
their maximum in October with, respectively, 1.32 m NGI 1 ;
1.19 and 1.13 m NGI. There is nearly steady flow
throughout the entire flooding period, becoming irregular
after November. The minimum heights are recorded in May

1

NGI measurements constitute the National Geographical Institute
measurements of the various water levels.