Diversity

The proliferation and variation in the reservoir size, purpose for their construction and the hydrological

Table 2 Physical and chemical characteristics of selected reservoirs of sub-Saharan Africa

Parameter

Volta (Ghana)

Kossou (Cote

Lagdo

Jebel Aulia

Mwandingusha

Kainji

Kariba (Zambia/

Cabora Bassa

d'Ivoire)

(Cameroon)

(Sudan)

(Zaire)

(Nigeria)

Zimbabwe)

(Mozambique)

Surface area (km2)

8502

1600

700

600

446

1270

6000 km2

2739 km2

Max. depth (m)

75 m

60

29

-

14

60

157

Mean depth (m)

18.8 m

14.3

11

-

11

20.9

Volume (km3)

148

20.5

7.7

-

1063

13.97

55.8 km2

Drainage area (km2)

385185

33000

-

-

1.6 x 106

56 925 km2

Altitude

85 m

204

216

378

1105.75

142

485 m

314

(m, asl)

Usage

Hydropower,

Fisheries and

Hydropower

Regulation of

Hydropower,

Hydropower,

Power generation,

Power generation,

transport,

aquaculture,

Nile irrigation

fisheries

fisheries

irrigation, potable

irrigation, potable

potable water,

hydropower

water, recreation,

water, recreation,

fisheries

transportation, fisheries

transportation, fisheries

Year of closure

1964

1971

1982

1937

1947

1968

1958

Rainfall (mm year-1)

-

1150-1400

-

-

-

-

Evaporation

-

2.4, 0.73

-

-

-

-

(km3. year-1)

Displacement time

4.3

5

-

-

-

-

0.54

(years)

Na+ (mg l -1)

5.8-6.4

3.9

-

3.07-6.0

1.8-5.2

K+ (mg l -1)

1.6-2.5

3.0

-

0.78-1.56

1.4-3.6

Ca2+ (mg l -1)

4.4-5.0

9.0

8-11

11.04-49.07

3.0-11.2

Mg2+ (mg l -1)

2.0-2.2

2.0

-

-

2.6-3.3

Cl-1 (mg l-1)

3-14

1.0-35.0

3.0

3-7

0.71-2.49

-

2.2

SO2- (mg l-1)

0.2-1.0

-

1

0.19-5.00

-

Alkalinity

24-36

55

65-70

-

0.45-0.69

(mg l-1)

PO- (mg l-1)

0.08-0.68

0.2-0.8

0

0.01-.25

9.0-18.0

0.02-10.6

Conductivity

70-180

80

160-330

128-309

46.6-99.6

(mS cm-1)

PH

6. 9-8.1

7.7-9.0

7.2

8.0-9.8

7.1-8.4

6-7.6

7.5-8.5

6.9-8.7

Figure 7 The general topography of Africa showing the main watersheds, the areas over 1000 m, and the approximate division between High and Low Africa (Adapted from Beadle, 1981).

Figure 7 The general topography of Africa showing the main watersheds, the areas over 1000 m, and the approximate division between High and Low Africa (Adapted from Beadle, 1981).

regime are so high that it is not possible to discuss each one of them separately. Thirteen reservoirs of over 300 km2 have been reviewed with respect to fisheries potential and the physico-chemical characteristics of some of them are given in Table 2.

Aquatic organisms have likewise adapted to spatial and temporal changes in the new habitats. The discontinuities between a riverine regime and lacustrine conditions are best illustrated in Jewel Aulia.

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