SIFRA BOOK 3
1. GEOGRAPHY AND CLIMATE
Algeria has a surface area of 2 381 740 km2. Most of the country (86%) is situated within the Sahara desert. In the north the Atlas Mountains, rising to a maximum elevation of 2 328 m asl, provide surface runoff to a narrow fertile coastal strip which supports most of the population.
Summers are hot; winters are fairly mild. Rainfall is adequate along the coast, but the interior is dry with extremes of desert temperatures.
The limited rainfall and runoff has fostered construction of storage dams to ensure adequate water supplies for crop irrigation. High salinities and irregular inflow limit the potential use of most natural lacustrine bodies.
2. HYDROLOGY
2.1 Lakes
There are no important freshwater lakes. Several internal drainage basins possess salt lakes and marshes. The largest basin, containing Lakes Chott Melshir and Chott Merouane, has a total area of 61 000 km2 with a mean annual inflow of 0.90 km3. Sebkha d'Oran is a large salt lake (296 km2) lying near the coast in the west. To the northeast is the Oubeira Lake, 21 km2. For most salt lake basins only a small proportion of the area has standing water.
2.2 Rivers, Floodplains and Swamps
There are eleven river (“oued”) basins which discharge into the Mediterranean Sea from a combined catchment area of 132 910 km2. The largest is the Oued Chelif (29 300 km2 catchment; 0.55 km3 discharge). There are two important floodplains: Garaet el Mkhada (89 km2) and Chott Zahrez Chergui.
2.3 Reservoirs
To date some 21 large dams have been constructed. Most are for irrigation usage, and a smaller number produce hydroelectricity or supply municipalities. At present little fishery development has taken place in these reservoirs.
2.4 Coastal Lagoons
There is one small lagoon in the extreme east of the country: Mellah.
2.5 Aquaculture
No data available on ponds situation.
3. FISHERY PRODUCTION/POTENTIAL
3.1 Fish production and per caput supply
Table 1. FISH PRODUCTION AND PER CAPUT SUPPLY - Algeria, 1970–1987
Nominal Domestic Production (t) 2 | Nominal Consumer Supply (kg/person) | ||||||||
Year | Population '000 1 | Inland capture | Aquaculture 3 | Marine capture | Total | Inland capture | Aquaculture 3 | Marine capture | Total |
1970 | 13 746 | 0 | - | 25 700 | 25 700 | 0 | - | 1.9 | 1.9 |
1971 | 14 173 | 0 | - | 23 800 | 23 800 | 0 | - | 1.7 | 1.7 |
1972 | 14 613 | 0 | - | 28 300 | 28 300 | 0 | - | 1.9 | 1.9 |
1973 | 15 067 | 0 | - | 31 200 | 31 200 | 0 | - | 2.1 | 2.1 |
1974 | 15 535 | 50 | - | 35 708 | 35 758 | 0.003 | - | 2.3 | 2.3 |
1975 | 16 018 | 0 | - | 37 693 | 37 693 | 0 | - | 2.3 | 2.3 |
1976 | 16 512 | 0 | - | 35 122 | 35 122 | 0 | - | 2.1 | 2.1 |
1977 | 17 018 | 0 | - | 43 475 | 43 475 | 0 | - | 2.5 | 2.5 |
1978 | 17 542 | 0 | - | 34 143 | 34 143 | 0 | - | 1.9 | 1.9 |
1979 | 18 090 | 0 | - | 38 678 | 38 678 | 0 | - | 2.1 | 2.1 |
1980 | 18 666 | 0 | - | 48 000 | 48 000 | 0 | - | 2.6 | 2.6 |
1981 | 19 240 | 0 | - | 56 000 | 56 000 | 0 | - | 2.9 | 2.9 |
1982 | 19 832 | 0 | - | 64 500 | 64 500 | 0 | - | 3.2 | 3.2 |
1983 | 20 441 | 0 | 5 4 | 65 000 | 65 005 | 0 | - | 3.2 | 3.2 |
1984 | 21 070 | 0 | 11 4 | 65 500 | 65 511 | 0 | - | 3.1 | 3.1 |
1985 | 21 718 | 0 | 14 4 | 66 000 | 66 014 | 0 | 0 | 3.0 | 3.0 |
1986 | 22 426 | 0 | 15 4 | 70 000 | 70 015 | 0 | 0 | 3.1 | 3.1 |
1987 | 23 156 | 241 | 17 4 | 70 000 | 70 258 | 0.01 | 0 | 3.0 | 3.0 |
1 Source: FAO
2 Source: FAO Fisheries Department FISHDAB
Summary data received in 1982 and 1986, but no detailed returns submitted since 1979.
3 - = data not available.
4 including marine and inland aquaculture (Vincke, 1989, pers.comm.)
3.2 Inland catch range and potential yield
Table 2.
Water body | Period | Annual catch range (t) | Potential annual yield (t) |
Oubeira Lake | 1974; 1981 | 100; 60 | - |
Medjerda River | - | - | - |
21 reservoirs | - | - | - |
Mellah Lagoon | 1972–75; 1981 | 20–82; 57 | - |
Total annual yield: 80–180 t
241 t in 1987 (see Table 1).
Fig. 1. MAP OF ALGERIA
4. STATE OF THE FISHERY
4.1 Yield
Recorded yields are relatively small. Some fishing undoubtedly occurs in the reservoirs but no data are available. Production from aquaculture, from 1983 to 1987, is given in Table 3 (Vincke, 1989, pers.comm.).
Table 3. AQUACULTURE PRODUCTION IN ALGERIA, BY SPECIES (t)
Species | 1983 | 1984 | 1985 | 1986 | 1987 |
Inland: | |||||
Cyprinus carpio | 5 | 2 | 3 | 3.5 | 4 |
Marine: | |||||
Penaeus kerathurus | - | 0.1 | 0.8 | 1 | 2 |
Crassostrea gigas | - | 5 | 5.5 | 5.5 | 6 |
Mytilus galloprovincialis | - | 4 | 4.5 | 5 | 5 |
Total | 5 | 11.1 | 13.8 | 15.0 | 17.0 |
4.2 Factors influencing yield
Fluctuations in catch in existing fisheries are largely due to problems in the maintenance of gear and boats and to climatic conditions.
4.3 Future development possibilities
Expansion of reservoir capture fisheries would appear to offer the most important possibility for inland fishery expansion. Increasing yields from the lagoons by introducing aquaculture practices would also appear feasible.
5. KEY BIBLIOGRAPHY
Lakes and lagoons: Lemoalle, 1987; Morgan, 1987
Sahara: Dumont, 1987
6. WATER BODIES DIRECTORY
Lakes | |||
Oubeira | |||
Rivers | |||
Medjerda | |||
Floodplains | |||
Garaet el Mkhada | Chott Zahrez Chergui | ||
Reservoirs | |||
Bakhadda | Erraguene | Ghrib | Meffrouch |
Beni Bahdel | Fergoug | Grande Kabylie | Merad |
Bou Hamidia | Fodda | Hamiz | Sarno |
Bouzzoul | Foum el Gherza | Irhil-Emda | Sidi Mahomed Ben Aouda |
Cheffia | Foum el Gueiss | Ksob | Zardezas |
Cheurfas | |||
Lagoons | |||
Mellah |
OUBEIRA LAKE
Geographical data (after Morgan, in Lemoalle, 1987) See Fig. 2. | |
Location: | northeast Algeria - 36°50'N; 8°23'E |
Surface area: | 21 km2 open water |
Depth: | 3 m (max) |
Fluctuation in level: | 2.5 m |
Total length: | 6 km |
Total width: | 3 km |
Distance from sea: | 3 km |
Major inflowing river: | flood in winter, through a channel from Oued el Kebir |
Outflow: | closed with a dam to keep the water in the lake. |
Physical and chemical data (after Morgan, in Lemoalle, 1987) | |
Temperature: | 11 to 12°C in winter; over 30°C in summer |
pH: | 7.2 to 7.6 |
Salinity: | 0.1 (January 1977) to 0.3 ‰ (March 1957) |
Fisheries data | |
No. of fish species: (after Morgan, in Lemoalle, 1987) | |
Coming from the sea, in winter, through Oued el Kebir: Mugilidae (3 species), Anguilla anguilla, Atherina sp., Alosa; Introduced: Gambusia affinis. | |
No. of fishermen: | 8 in 1982 |
There is one commercial fishery. |
Total annual catch and effort:
Year | Total catch (t) | No.of fishermen |
1974 | 100 | - |
1981 | 61 | - |
1982 | - | 8 |
Fig. 2. LAKES AND SWAMPS COMPLEX OF THE KALA REGION
(after Lemoalle, 1987)
MEDJERDA RIVER
(International water)
Geographical data | |
Source: | Algeria |
Total length: | 305 km (80 km in Algeria; 225 km in Tunisia) |
Countries traversed: | Algeria, Tunisia |
Major tributary: | Mellegue |
Discharges to: | Mediterranean Sea - 37°6'N; 10°14'E |
Special features: | Mellegue Reservoir on Mellegue tributary in Tunisia. |
GARAET EL MKHADA FLOODPLAIN
Geographical data (after Lemoalle, 1987) See Fig. 2 | |
Location: | Algeria - 36°48'N; 8°00'E |
Altitude: | 1 m asl |
Surface area: | 89 km2 |
Depth: | 0.3 m (mean, variable) |
Major inflowing rivers: | Oued el Kebir, Oued Bou Namoussa, Oued Chourka Garaet |
Outflow: | short channel to the sea |
Special features: | becomes almost dry from June to November; the water is fresh to hypo-saline. |
Physical and chemical data (Lemoalle, 1987) | |
Temperature: | 17°C in winter (January 1977) |
Salinity: | 4.6 ‰ in winter (January 1977) |
Fisheries data | |
No. of fish species: (Lemoalle, 1987) | |
Mugilidae; Anguillidae, Cyprinodon fasciatus, Atherina sp. (Mugilidae and Anguillidae are exploited.) |
CHOTT ZAHREZ CHERGUI FLOODPLAIN
Geographical data (after Lemoalle, 1987) | |
Location: | Algeria - 35°14'N; 3°32'E |
Altitude: | 900 m asl |
Surface area: | 250 km2 total (66% max. open water) |
Depth: | 3 m (max.) |
Inflowing rivers: | several small rivers, after heavy rains |
Outflow: | there is no outflow |
Special features: | salt water; salt concentration increasing to saturation when the Chott dries up. |
Fisheries data | there are no fish. |
BAKHADDA RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 45 m |
Volume: | 45 × 106 m3 |
Outflowing river: | Mina |
BENI BAHDEL RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 55 m |
Volume: | 42 × 106 m3 at USL |
Outflowing river: | Tafna |
BOU HAMIDIA RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 50 m |
Volume: | 52 × 106 m3 |
Outflowing river: | El Hammam |
BOUZZOUL RESERVOIR
Geographical data | |
Location: | Algeria |
CHEFFIA RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 51 m |
Volume: | 170 × 106 m3 at USL |
Outflowing river: | Bou Namoussa |
CHEURFAS RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 29 m |
Volume: | 8 × 106 m3 at USL |
Outflowing river: | Mekerra |
ERRAGUENE RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 76 m |
Volume: | 200 × 106 m3 |
Outflowing river: | Djendjen |
FERGOUG RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 50 m |
Volume: | 18 × 106 m3 |
Outflowing river: | El Hammam |
FODDA RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 85 m |
Volume: | 228 × 106 m3 at USL |
Outflowing river: | Fodda |
FOUM EL GHERZA RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 65 m |
Volume: | 43 × 106 m3 at USL |
Outflowing river: | El Abiod |
FOUM EL GUEISS RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 235 m |
Volume: | 3 × 106 m3 |
Outflowing river: | Gueiss |
GHRIB RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 65 m |
Volume: | 280 × 106 m3 |
Outflowing river: | Cheliff |
GRANDE KABYLIE RESERVOIR
Geographical data | |
Location: | Algeria |
HAMIZ RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 45 m |
Volume: | 15 × 106 m3 |
Outflowing river: | Hamiz |
IRHIL-EMDA RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 85 m |
Volume: | 127 × 106 m3 at USL |
Outflowing river: | Agrioun |
KSOB RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 32 m |
Volume: | 8 × 106 m3 at USL |
Outflowing river: | Ksob |
MEFFROUCH RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 26 m |
Volume: | 15 × 106 m3 at USL |
Outflowing river: | Meffrouch |
MERAD RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 23 m |
Volume: | 1 × 106 m3 at USL |
Outflowing river: | Bou Djabroun |
SARNO RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 27 m |
Volume: | 22 × 106 m3 at USL |
Outflowing river: | Sarno |
SIDI MAHOMED BEN AOUDA RESERVOIR
Geographical data | |
Location: | Algeria |
Outflowing river: | Mina |
ZARDEZAS RESERVOIR
Geographical data | |
Location: | Algeria |
Dam height: | 37 m |
Volume: | 10 × 106 m3 at USL |
Outflowing river: | Safsaf |
MELLAH LAGOON
Geographical data | (after Lemoalle, 1987) See Fig. 2 |
Location: | Algeria - 36°53'N; 8°20'E |
Altitude: | 1 m asl |
Surface area: | 8.79 km2 |
Depth: | 6 m (max); 3.5 m (mean) |
Max. length: | 4 km |
Max. width: | 2 km |
Major inflowing river: | in winter: floodings from Oued el Aroug and Oued el Melah; also underground water |
Outflow: | 900-m-long channel to Mediterranean Sea |
Special feature: | in summer, the Oueds become dry, the lagoon level decreases, and sea water enters. |
Physical and chemical data | |
Surface temperature: | 12–28°C |
Salinity: | 25–27 ‰ |
8.5 ‰ (January 1977) | |
Fisheries data | |
No. of fish species (Lemoalle, 1987): | |
Originating from the sea: Mugilidae, Dicentrarchus labrax, Solea, Sparus aurata Introduced: Gambusia holbrooklii | |
Yield: | 50 kg/ha in 1971 (Lemoalle, 1987) |
Total annual catch and effort:
Year | Total catch (t) | No.of fishermen |
1971 | 42 | - |
1972 | 20 | - |
1973 | 41 | - |
1974 | 81 | - |
1975 | 82 | - |
1976 | 38 | - |
1977–80 | - | - |
1981 | 57 | - |
1982 | - | 13 |
7. BIBLIOGRAPHY
Dumont, 1987
Lemoalle, 1987
Morgan, 1987
1. GEOGRAPHY AND CLIMATE (Welcomme, 1979)
Chad (with a surface area of 1 284 000 km2) is shaped like a shallow basin cut in half. Lake Chad itself lies at the bottom with an altitude of 280 m. The land rises to the north (where the Tibesti Mountains reach altitudes as high as 3 400 m), to the east to the highlands of Sudan, and to the south to the Chari watershed. The southwest of the country is heavily wooded, but the country rapidly becomes desertic toward the north.
Most of the southern Chad has a prolonged rainy season; heavy rains last from April through October. Nearer the centre of the country the season becomes shorter (June-September), and north of Lake Chad there is little rainfall.
The south of Chad has an agrarian population, living mainly on subsistence agriculture. The north is desert and inhabited only by nomadic tribes. The Sahelian transitional savanna is used mainly by pastoral peoples for grazing cattle, sheep and goats.
2. HYDROGRAPHY (see Figs. 1, 2 and 3)
2.1 Lakes (Welcomme, 1979)
Lake Chad fluctuates in area in a pronounced cycle thought to be some 25 years long. This lake exists in two phases: the Greater Chad in pluvial periods, and the Lesser Chad in drought. During its Greater Chad phase, half of the lake's 22 000 km2 lies within the country. In its more recent (1978) diminished state, about 1 200 km2 of the remaining 2 000 km2 of open water were left around the mouth of the Chari River. Apart from Lake Chad itself, there are several smaller lakes. In the Chad Basin there is Lake Iro (situated on the Salamat River floodplain, which extends over 200 km2), and Lake Fitri (a Lake Chad in miniature to the east of the main lake, which extends over 420 km2 but can reach 1 200 km2 in the rainy season). There are a further four small lakes lying along the Toubouri Depression of the Mayo Kebi River in the flood season, but during the dry period these are much smaller. Lake Tikem has an area of 14 km2; Lake Fianga, 28 km2; Lake Lere, 40.5 km2; and Lake Trene, 12 km2.
2.2 Rivers, Floodplains and Swamps (Welcomme, 1979)
The whole of southern Chad is dominated by the Chari River system which, with its main tributaries, the Salamat and Azoum Rivers, extends over about 1 200 km. There are extensive swamps over most of the Chari Basin which are drained by such rivers as the Erguig and Aouk. These swamps have been estimated as covering about 80 000 km2. The Chari combines with the Logone to discharge into Lake Chad. The Logone possesses the large Yaèrè floodplain. (See Fig. 3, p.21.)
2.3 Reservoirs
There are no important impoundments in Chad.
2.4 Coastal Lagoons
None; Chad is landlocked.
2.5 Aquaculture
There is no aquaculture in Chad (Vincke, 1989, pers. comm.).
3. FISHERY PRODUCTION/POTENTIAL
3.1 Fish production and per caput supply
Table 1. FISH PRODUCTION AND PER CAPUT SUPPLY Chad, 1970–1987
Nominal Production (excluding export) (t) 2 | Nominal Consumer Supply (excluding imports/exports) (kg/person) | ||||
Year | Population '000 1 | Inland capture '000 | Aquaculture 3 | Total '000 | Total inland |
1970 | 3 652 | 120 | 120 | 32.9 | |
1971 | 3 725 | 120 | 120 | 32.2 | |
1972 | 3 799 | 130 | 130 | 34.2 | |
1973 | 3 874 | 105 | 105 | 27.1 | |
1974 | 3 951 | 115 | 115 | 29.1 | |
1975 | 4 030 | 115 | 115 | 28.5 | |
1976 | 4 113 | 115 | 115 | 28.0 | |
1977 | 4 199 | 115 | 115 | 27.4 | |
1978 | 4 288 | 115 | 115 | 26.8 | |
1979 | 4 381 | 115 | 115 | 26.2 | |
1980 | 4 477 | 115 | 115 | 25.7 | |
1981 | 4 577 | 115 | 115 | 25.1 | |
1982 | 4 681 | 115 | 115 | 24.6 | |
1983 | 4 789 | 110 | 110 | 23.0 | |
1984 | 4 901 | 110 | 110 | 22.4 | |
1985 | 5 018 | 115 | 115 | 22.9 | |
1986 | 5 142 | 110 | 110 | 21.4 | |
1987 | 5 269 | 110 | 110 | 20.9 |
1 Source: FAO
2 Source: FAO Fisheries Department FISHDAB
The 1970–87 catch data are estimates provided by the national reporting office.
3 No aquaculture in Chad (Vincke, 1989, pers.comm.)
Considerable statistical confusion arises from the situation around Lake Chad. The best estimate of production from the basin over the last few decades is given below (but these are at best speculative).
Table 2. ESTIMATES OF TOTAL PRODUCTION FROM LAKE CHAD BASIN
(all countries) (t)
Year | Lake | Rivers | Total |
1950 | 20 000 | 70 000 | 90 000 |
1960 | 30 000 | 75 000 | 105 000 |
1961–66 (p.a.) | 35 000 | 80 000 | 115 000 |
1967 | 35 000 | 85 000 | 120 000 |
1968 | 40 000 | 80 000 | 120 000 |
1969 | 40 000 | 75 000 | 115 000 |
1970 | 55 000 | 60 000 | 115 000 |
1971 | 85 000 | 50 000 | 135 000 |
1972 | 120 000 | 40 000 | 160 000 |
1973 | 150 000 | 40 000 | 190 000 |
1974 | 65 000 | 50 000 | 115 000 |
1975 | 50 000 | 60 000 | 110 000 |
Source: Stauch (1977)
Fig. 1. MAP OF CHAD
These estimates correspond roughly to the figures advanced by the Government of Chad as reflected in the nominal catches. It may be assumed, therefore, that Chad has laid claim to the total production from Lake Chad Basin, whereas in fact only a proportion of the catch originates within Chadian territory. In the case of the lake, Chad has between 50% and 60% of the waters and these are among the richest and most productive. Furthermore, Cameroon probably produces between 20 000 and 30 000 t from the Yaèrès floodplain and the river production should be diminished by this amount. Seen in this light, the Republic of Chad was probably producing about 50 000 t of fish in the 1950's, 70 000 t in the 1960's, up to 100 000 t during the earlier years of the drought, and about 50 000 t in the late 1970's (Welcomme, 1979).
3.2 Inland catch range and potential yield
Table 3.
Water body | Period | Annual catch range (t)* | Potential annual yield (t) | |
Lake Chad | 1969; 1973 | 10–75 000 | no data | |
Bahr Aouk and Salamat Rivers and associated swamps | - | 22 000 | ||
Chari and Logone Rivers and Yaèrès floodplain | - | 35 000 | ||
No data available for: | ||||
Lakes Fianga, Fitri, Iro, Lere, Tikem and Trene; Ouham River. |
Total annual yield: 50 000 (Welcomme, 1979)
110 000 (National reporting office, current).
4. STATE OF THE FISHERY (Welcomme, 1979)
4.1 Yield
The present state of the fishery of Lake Chad is very poor. The lake itself has never recovered from the 1972–74 drought and is still in its small phase. The fish population of the rivers were damaged by the changes in flood regime during the droughts and the fisheries there are also diminished.
4.2 Factors influencing yield
As with the other countries of the Sahelian belt, the main factor influencing the fishery is rainfall. This had an especially severe effect during the latest dry period when catches rose sharply as the lake decreased (1972–73) but fell sharply as the stocks of the small lake were unable to support the intensive effects of the same number of fishermen who were previously dispersed over ten times the area. In the rivers, too, the failure of two or more successive floods virtually exterminated several of the major migratory species, leading to a disequilibrium in population structure. Continuing adverse conditions have tended to change the population structure, with a progressive disappearance of the more migratory species.
4.3 Future development possibilities
No amelioration of the fisheries in the Lake Chad Basin can be anticipated so long as the present hydrological regime persists. However, historically, the lake has always recovered from these dry spells and it can be expected to regain its Large Chad phase of 22 000 km2 during the next wet cycle. In that case the potential catch might be expected to exceed past yield (at 100 kg/ha, the lake should produce over 200 000 t), but only if the fishery relaxes its intensity sufficiently for the fish stock to build itself up. The floodplains, too, can be expected to return a better yield, although the potential needs clarification (at as little as 10 kg/ha the 90 000 km2 of the Chari/Logone floodplains could produce 90 000 t).
5. KEY BIBLIOGRAPHY
Sahara-Northern Chad: Dumont, H.J., 1987
Chad Basin: Lèvêque, C., 1987
6. WATER BODIES DIRECTORY
Lakes | |||
Chad | Fitri | Lere | Trene |
Fianga | Iro | Tikem | |
Rivers | |||
Bahr Aouk | Logone | Salamat | |
Chari | Ouham |
LAKE CHAD
(International water)
Geographical data | |||
Location: | 12° 30' –14° 30' N; 13° 00' – 15° 30' E (See Fig. 2) Cameroon, Chad, Niger, Nigeria | ||
Surface area: | 2 000–22 000 km2 The dimensions of Lake Chad vary with the rainfall over its basin. The lake seems to exist in two phases: the “Normal Chad” phase, with an area of about 18 000 km2, and the “Little Chad” phase, with an area of about 2 000 km2. In 1907 the northern parts dried out completely and, although by 1961 the level had risen markedly (and reached an area of 22 000 km2), the lake was once again reduced in area to reach a minimum in 1973. The level has since risen slightly, but the northern part still remained unflooded in 1983. The hydrographic system now formed by Lake Chad and its rivers is the remnant of what was once probably the greatest lake in the world. | ||
During the “Normal Chad” phase, the area of open water is distributed as follows: | |||
(Welcomme, 1972) | |||
Chad | 11 000 km2 (50%) | ||
Nigeria | 5 500 km2 (25%) | ||
Niger | 3 898 km2 (17%) | ||
Cameroon | 1 800 km2 ( 8%) | ||
During the “Little Chad” phase, the area of open water is distributed as follows: | |||
Chad | 1 200 km2 (60%) | ||
Cameroon | 800 km2 (40%) |
(*indicates data are for “Normal Chad” phase) | ||
Depth: | 9.5 m (max); 3.9 m (mean) | |
Volume: | *75 km3 | |
Max. length: | *224 km | |
Max. width: | *144 km | |
Shoreline: | *1 000 km | |
Annual fluctuation in level: *1 m approx | ||
Catchment area: | 2 500 000 km2 | |
Major inflowing rivers: Chari, Yobe, Komadougou, Ngadd, Yedseram | ||
Physical and chemical data (all data are for “Normal Chad” phase) | ||
Conductivity: | Conductivity increases from K20 50 μS/cm (open waters at Chari mouth), to K20 1 000 μS/cm (vegetated areas) (Welcomme, 1972); see also Table 4. | |
Surface temperature: | 18.7–32.3°C (Dussart, 1969) | |
pH: | 7.1–8.3 (Dussart, 1969); see also Table 4 | |
Ionic composition: | See Table 4. | |
Fisheries data | ||
No. of fish species: | 83 (Blache et al., 1964) | |
No. of fishermen:* | about 10 000 (dates unspecified) (Welcomme, 1972) | |
Chad | 5 000 | |
Nigeria | <3 000 | |
Niger | 1 000 | |
Cameroon | >1 000 |
Total annual catch and effort: | ||
Catch by country is very obscure because of the free movement of fishermen and produce around the lake. The catch history for 1969–85 has been estimated as follows by Stauch (1977) (Table 5), and by Sagua (1986) (Table 6). | ||
Approximate estimates for the catch from the Lake prior to the 1972–74 Sahelina drought (during the Normal Chad phase) are given as follows by Welcomme (1979): | ||
Chad | 50 000 t | |
Nigeria | 25 000 t | |
Niger | 10 000 t | |
Cameroon | 5 000 t |
Fig. 2. LAKE CHAD
(Welcomme, 1972)
Table 4. CHEMICAL COMPOSITION OF WATERS DURING “NORMAL” CHAD PERIOD IN MAIN LAKE ZONES
(cited in Lévêque, 1987)
Values are in meq/l when not otherwise specified.
Values between parentheses () are approximate and deducted from evaporation experiments.
Zones | Cond. 10μS/cm | pH | Na | K | Ca | Mg | Total cations | Alc | Cl | SO4 | Total anions | PO4 10μg/l | H4SiO4 mM/l | Salinity mg/l |
Archipelago north | 687 | 8.7 | 2.83 | 0.86 | 2.09 | 1.72 | 7.30 | 7.34 | (0.40) | (0.15) | 7.89 | 1000–3000 | 1.06 | 695 |
North islets/banks | 725 | 8.7 | 2.82 | 0.82 | 2.36 | 1.98 | 7.98 | 7.74 | (0.35) | (0.14) | 8.23 | n.d. | 1.02 | 700 |
Open waters north | 407 | 8.1 | 1.59 | 0.47 | 1.32 | 1.10 | 4.48 | 4.35 | (0.23) | (0.07) | 4.65 | 100–1200 | 0.73 | 415 |
Archipelago east | 237 | 7.7 | 0.84 | 0.24 | 0.91 | 0.59 | 2.58 | 2.53 | (0.11) | (0.05) | 2.69 | 500–1200 | 1.08 | 280 |
Great Barrier | 190 | 8.0 | 0.68 | 0.21 | 0.66 | 0.52 | 2.07 | 2.03 | (0.09) | (0.03) | 2.15 | n.d. | 0.73 | 216 |
Archipelago southeast | 105 | 7.4 | 0.32 | 0.10 | 0.44 | 0.32 | 1.18 | 1.15 | (0.05) | (0.02) | 1.22 | 100–400 | 0.64 | 135 |
Open waters south | 83 | 7.2 | 0.28 | 0.09 | 0.32 | 0.24 | 0.93 | 0.89 | (0.04) | (0.01) | 0.94 | n.d. | 0.50 | 109 |
Southeast islets/banks | 87 | 7.4 | 0.24 | 0.08 | 0.36 | 0.29 | 0.96 | 0.93 | (0.04) | (0.01) | 0.98 | n.d. | 0.53 | 110 |
Southeast open waters | 58 | 7.2 | 0.16 | 0.06 | 0.24 | 0.18 | 0.64 | 0.62 | (0.04) | <0.01 | 0.67 | 10–250 | 0.41 | 77 |
Chari | 60 | 7.3 | 0.13 | 0.05 | 0.20 | 0.15 | 0.53 | 0.52 | (0.03) | <0.01 | 0.56 | n.d. | 0.37 | 66 |
Table 5. FISH PRODUCTION FROM LAKE CHAD *
Chad | Nigeria | Whole Lake | |||
Year | N'Djamena (t) | % total | Baga (t) | % total | Total production (t) |
1969 (6 mos.) | 8 800 | 30.6 | 20 000 | 69.4 | 28 800 |
1970 | 18 700 | 28.5 | 46 800 | 71.5 | 65 500 |
1971 | 28 700 | 25.0 | 86 300 | 75.0 | 115 000 |
1972 | 42 300 | 25.5 | 123 400 | 74.5 | 165 700 |
1973 | 37 900 | 19.8 | 153 600 | 80.2 | 191 500 |
1974 | 47 400 | 21.5 | 172 600 | 78.5 | 220 000 |
1975 | 44 400 | 34.4 | 84 500 | 65.6 | 128 900 |
1976 | 39 700 | 36.7 | 68 500 | 63.3 | 108 220 |
1977 (6 mos.) | 14 800 | 28.5 | 37 200 | 71.5 | 52 000 |
Mean annual STD | 27.83 | 72.17 | |||
5.25 | 5.25 |
Fig. 3. RIVERS AND LAKES OF THE CHAD BASIN
(Welcomme, 1972)
Table 6. PRODUCTION FROM LAKE CHAD* (at Baga, 1978–85)
Year | Nigeria (t) 1 | Whole Lake (t) 2 |
1978 | 70 698 | 100 997 |
1979 | 67 817 | 96 881 |
1980 | 64 886 | 92 694 |
1981 | 58 222 | 83 174 |
1982 | 15 193 | 21 704 |
1983 | 21 379 | 30 541 |
1984 | 28 446 | 40 637 |
1985 | 21 934 | 31 334 |
1 Source: Federal Department of Fisheries, Lagos
2 Baga figure multiplied by 100/70.
* Production figures obtained from road traffic census of processed fish at entry to Maiduguri: Baga, from 1978 to 1985, in fresh weight equivalent (conversion factor of 4.5). (Sagua, 1986)
Potential annual yield:
In entire lake:
100–120 kg/ha (Durand, 1980)
70 000 t/yr maximum sustainable yield (Moses, 1982)
in “normal” 20 000 km2 Chad:
80–100 kg/ha;
160 000 t to 200 000 t/yr (Van der Meeren, 1980).
In Nigerian waters:
41 250–55 000 t/yr (Ajayi & Talabi, 1984).
By country, assuming a productivity of 80 to 120 kg/ha/yr:
80 kg/ha | - | 120 kg/ha | |||
in Chad | |||||
Normal Chad phase | (11 000 km2) | 88 000 | - | 132 000 t | |
Little Chad phase | ( 1 200 km2) | 9 600 | - | 14 400 t | |
in Nigeria | |||||
Normal Chad phase | (5 500 km2) | 44 000 | - | 66 000 t | |
Little Chad phase | (0 km2) | 0 t | |||
in Niger | |||||
Normal Chad phase | (3 898 km2) | 31 184 | - | 46 776 t | |
Little Chad phase | (0 km2) | 0 t | |||
in Cameroon | |||||
Normal Chad phase | (1 800 km2) | 14 400 | - | 21 600 t | |
Little chad phase | (800 km2) | 6 400 | - | 9 600 t |
LAKE FIANGA
(International water)
Geographical data | ||
Location: | Cameroon, Chad - 9°54'–10°06'N; 15°13'E (see Fig. 4) | |
Surface area: | 28 km2 (17 km2 in Cameroon; 11 km2 in Chad) | |
Max. length: | 23 km | |
Max. width: | 1.5 km | |
Major inflowing river: | Mayo Kebi | |
Outflowing river: | Mayo Kebi | |
Depth: | 4 m (max. at low water) (Lèvêque, 1987) | |
Physical and chemical data (in Lèvêque, 1987) | ||
pH: | 7.5 | |
Conductivity: | 85 μS/cm | |
Ionic composition: | (meq/l) | |
HCO3 | 2.27 | |
Cl | 0.06 | |
Na | 0.89 | |
K | 0.25 | |
Ca | 0.84 | |
Mg | 0.52 | |
SiO2 | 13.0 mg/l | |
Fisheries data | ||
No. of fish species: | about 100 (Blache, et al., 1964) | |
Note: | fishery activity exists, but no statistical data are available (Lèvêque, 1987). |
Fig. 4. LAKES OF THE TOUBOURI DEPRESSION
(Lèvêque, 1987)
LAKE FITRI
Geographical data | |
Location: | Chad - 12°52'N; 17°29'E |
Surface area: | 420–1 200 km2 |
Major inflowing river: | Batha |
Outflowing river: | None - landlocked |
LAKE IRO
Geographical data (Welcome, 1972) | |
Location: | Chad - 10°8'N; 19°22'E |
Surface area: | 200 km2 |
Major inflowing river: | Salamat |
Outflowing river: | Salamat |
LAKE LERE
Geographical data (Welcomme, 1972; Lèvêque, 1987) (See Fig. 5) | |
Location: | Chad - 9° 37'N; 14°10'E |
Altitude: | 231 m |
Surface area: | 40.5 km2 |
Depth: | 8 m (max); 4.5 m (mean) |
Volume: | 160 × 106 m3 |
Max. length: | 13 km |
Max. width: | 4.8 km |
Major inflowing river: | Mayo Kebi |
Outflowing river: | Mayo kebi |
Physical and chemical data (Lèvêque, 1987) | ||
Surface temperature: | 20.5–25.2°C | |
Conductivity: | K25 89 μ S/cm | |
pH: | 8.0 | |
Ionic composition: | meq/l | |
Na | 0.10 | |
K | 0.05 | |
Ca | 0.50 | |
Mg | 0.22 | |
HCO3 | 0.90 | |
SiO2 | 32.00 mg/l |
Fig. 5. BATHYMETRIC MAP OF LERE LAKE
(Lèvêque, 1987)
LAKE TIKEM
Geographical data | ||
Location: | Chad - 9°48'N; 15°5'E (see Fig. 4) | |
Surface area: | 14 km2 | |
Max. length: | 14 km | |
Max. width: | 2 km | |
Major inflowing river: | Mayo kebi | |
Outflowing river: | Mayo kebi | |
Physical and chemical data (in Lèvêque, 1987) | ||
Conductivity: | 83 μ S/cm | |
pH: | 7.15 | |
Ionic composition: | meq/l | |
HCO3 | 1.22 | |
Cl | 0.07 | |
Na | 0.21 | |
k | 0.12 | |
Ca | 0.50 | |
Mg | 0.43 | |
SiO2 | 20.5 mg/l | |
Fisheries data | ||
No. of fish species: | about 100 (Blache, et al., 1964) |
LAKE TRENE
Geographical data | |
Location: | Chad - 9°39'N; 14°17'E |
surface area: | 12 km2 |
Max. length: | 8 km |
Max. width: | 2.5 km |
Major inflowing river: | Mayo Kebi |
Outflowing river: | Mayo Kebi |
BAHR AOUK RIVER
(International water)
Geographical data | |
Source: | extreme southeastern Chad |
Altitude: | 749 m asl |
Total length: | 620 km |
Countries traversed: | Chad, Central African Republic |
Major tributary: | Bahr Kameur |
Discharges to: | unites with the Bamingui to form the Chari |
Special features: | possesses extensive lateral floodplains dotted with numerous small lakes along much of its length. |
Fisheries data | |
Total annual catch: | in Chad, the composite catch from the Salamat River, Bahr Aouk and associated swamps is 22 000 t. |
CHARI RIVER AND YAERES FLOODPLAIN
(International water)
Geographical data (data mainly from Welcomme, 1972) | ||
Source: | the Chari River is formed from the confluence of several rivers, principally the Salamat, Bahr Aouk and Ouham. | |
Total length: | 950 km | |
Drainage area: | 600 000 km2 (N'Djamena) | |
Countries traversed: | Cameroon, Chad, Central African Republic (Bahr Aouk, Ouham and many other tributaries), Sudan (Wadi Tirwal, Bahr Azoum) | |
Discharges to: | Lake Chad | |
Volume of discharge at mouth: 1 011–1 181 m3/sec | ||
Flood regime: | floods from July to February, maximum in October | |
Special features: | the Chari has extensive floodplains along most of its course. The main areas are centered around the Salamat and Erguig Rivers. The total area of the Chari/Logone floodplains is about 90 000 km2. | |
Physical and chemical data | ||
Temperature: | 19.4–30.4°C | |
Conductivity: | K24 42–73 μ S/cm | |
pH: | 6.9–7.7 | |
Ionic composition: | mg/l | |
Na | 2.92 | |
K | 1.84 | |
Ca | 2.06 | |
Mg | 0.94 | |
CO3 | 31.5 | |
Si(OH)4 | 22.2 | |
Fisheries data | ||
Total annual catch: | the catch from the Chari/Logone system, which originates mainly from the Yaèrès floodplain (4 600 km2) of the Logone River was estimated (in the early 1960's) at 20–30 000 t from Cameroon and 35 000 t from Chad (Blache & Miton, 1962). The status of this fishery changed during the Sahelina drought, when much of the plain was left unflooded. |
LOGONE RIVER AND YAERES FLOODPLAIN
(International water)
Geographical data (Welcomme, 1972) | |
Source: | Cameroon (Mbèrè tributary) - 6° 54'N; 14° 15'E |
Total length: | 550 km |
Drainage area: | 73 700 km2 (at Bongor) |
Countries traversed: | Cameroon, Chad |
Discharges to: | Chari River at N'Djamena |
Volume of discharge at mouth: 40–3 000 (mean: 1 500) m3/sec | |
Flood regime: | floods in June-January, maximum in September-October |
Special features: | Yaèrès floodplain |
Physical and chemical data (Welcomme, 1972) | |
Conductivity: | K24 41–82 μ S/cm |
Fisheries data | |
Total annual catch: | the catch from the Chari/Logone system, which originates mainly from the Yaèrès floodplain (4 600 km2) of the Logone River was estimated (in the early 1960's) at 20–30 000 t from Cameroon and 35 000 t from Chad (Blache & Miton, 1962). The status of this fishery changed during the Sahelina drought, when much of the plain was left unflooded. |
Fig. 6. SALAMAT RIVER AND FLOODPLAIN
(Lèvêque, 1987)
OUHAM RIVER
(International water)
Geographical data | |
Source: | Karre Mountains, western Central African Republic |
Altitude: | 1 220 m asl |
Total length: | 790 km |
Countries traversed: | Central African Republic, Chad |
Major tributaries: | Bobo, Nanna Bakassa |
Discharges to: | Chari |
Special features: | possesses a lateral floodplain with numerous small lakes along its lower 160 km. |
SALAMAT RIVER AND FLOODPLAIN
Geographical data | (see Fig. 6) |
Source: | eastern Chad |
Altitude: | 1 140 m asl |
Total length: | 950 km |
Countries traversed: | Chad |
Major tributaries: | Bahr Bola, Bahr Azoum |
Discharges to: | Chari |
Special features: | Lake Iro, extensive lateral floodplains and swamps. |
Specific reference: | Lèvêque, 1987 |
Fisheries data | |
Total annual catch: | in Chad the Salamat, the Bahr Aouk and associated swamps yield approximately 22 000 t. |
7. Bibliography
Ajayi & Talabi, 1984
Blache, et al., 1964
Blache & Miton, 1962
Dumont, 1987
Durand, 1980
Dussart, 1969
Lèvêque, 1987
Moses, 1982
Sagua, 1986
Stauch, 1977
Van der Meeren, 1980
Welcomme, 1972; 1979