COUNTRY FILES (Contd.)

ZIMBABWE

1. GEOGRAPHY AND CLIMATE

Zimbabwe (with a surface area of 386 670 km²) is a landlocked country, straddling the high plateau between the Zambezi and Limpopo rivers. The plateau consists of three relief regions: the high veld (over 1 200 m); the middle veld (915 to 1 220 m) and the low veld (below 915 m). The latter comprises the Zambezi basin in the north and the bigger Limpopo and Sabi-Lundi basins in the south and southeast, respectively.

The three relief regions have undulating plateaus with surfaces broken locally by rock formations, some of which are large landforms such as the Great Dyke (480 km long by 10 km wide). The border with Mozambique constitutes a fourth relief region known as the Eastern Highlands. This region marks the uplifted edge of the tableland of south-central Africa and is extremely mountainous, with many peaks exceeding 1 800 m (i.e., Mt. Inyangani: 2 594 m).

This wide range of altitude tends to moderate temperatures. On the high veld, mean monthly temperatures range from 13°C (July) to 22°C (October). Comparative values for the low-lying Zambezi Basin are 20°C to 30°C. Rainfall varies but is insufficient. It is restricted to the period between November and March. In the Eastern Highlands, the mean annual rainfall is 1 400 mm, while the northeastern highveld and the Limpopo basin receive about 800 and 400 mm, respectively.

The wide range of rainfall and the mixture of physical formations have given rise to the following different agricultural regions:

1. diversified farming on the high and middle velds;
2. intensive crop production, as for (a);
3. extensive livestock farming (wet areas);
4. extensive ranching (semi-arid areas); and
5. land unsuitable for agriculture (4%).

Over 70% of the total population is agrarian and agriculture provides about 50% of the country's foreign exchange earnings. Mining accounts for 40%; the remaining percentage comes from manufacturing, tourism and other small industries.

2. HYDROGRAPHY

2.1 Lakes

There are no natural lakes of any significant size in Zimbabwe.

2.2 Rivers, Floodplains and Swamps

Rivers form the bulk of Zimbabwe's surface water resources and have a mean annual runoff exceeding 20.1 × 10⁹ m³. River flows are variable and characteristically seasonal, with the largest flows occurring during the rainy season (November to March). There are seven major river systems within Zimbabwe which carry about 65% of its runoff, while the balance (35%) originates from the country's northern (Zambia) and southern (South Africa) borders.

Zimbabwe can be divided into six hydrological zones (shown in Table 1), each of which is well provided with gauging weirs and flow-measuring devices. In 1975 there were about 866 gauging weirs, the earliest of which dates back to 1907.

Table 1. MAJOR RIVER SYSTEMS AND HYDROLOGICAL ZONES IN ZIMBABWE (Balarin, 1984)

^a Thornton, 1980
^b Mitchell, 1977
^c Bell-Cross, 1976

(1100) = mean annual runoff, million cubic metres

Fig. 1. MAJOR RIVERS AND DRAINAGE BASINS
(Bell-Cross, 1976; Mitchell, 1977)

Figure 3 shows the location of the floodplains of Zimbabwe. The largest floodplain is the Mana Pools in the Zambezi River between Kariba and Mpata gorges. Floodplains are prone to periodic flooding along the banks of rivers and little is known of their limnological or fishery potential.

2.3 Reservoirs (Balarin, 1984)

There exist about 120 large dams (as classified by the International Commission on Large Dams/ICOLD). The total capacity is over 3 900 million m³. Cayron and De Fooz (1981) indicate 121 dams of 4 088 million m³. These have been mainly constructed by the Ministry of Water Development for domestic, industrial and hydroelectric purposes. In 1979, some 7 400 small dams of varying sizes, with a total storage capacity of 4 700 million m³, had been constructed (Grizic, 1980). Of these, 5 800 small dams had been built by the private sector, mainly in the farming areas (an estimated 21–45 000 ha of surface water, or 446 million m³) (Kenmuir, 1981b). Cayron and De Fooz (1981) consider all sizes of small dams and suggest that these are over 14 511, with a total capacity of 5 236 million m³. This could perhaps include the weirs described by Bowmaker (1975). The location of some of the major dams of over 10 million m³ capacity are shown in Figure 2 and described in Table 2 (Thornton, 1980). The 34 dams listed have been the subject of limnological studies and their uses are also indicated.

Over 8 000 small dams now exist, of which 75% are private farm dams. These impoundments are shallow, monomictic (overturn in April), and highly seasonal water bodies. Evaporation losses from a dam average 1 800 mm/yr (Mitchell, 1977). This, coupled with water use, causes dramatic seasonal fluctuations. The nutrient load is low (meso-oligotrophic status), though water quality in certain impoundments is affected by man. Lake McIlwaine, for example, used to receive processed sewage from Hahare and became highly eutrophic.

2.4 Coastal Lagoons

None; Zimbabwe is landlocked.

3. FISHERY PRODUCTION/POTENTIAL

3.1 Aquaculture (mainly adapted from Balarin, 1984)

Fish farming trials were first undertaken in 1950. In 1956, the first fish culture research station was built at Henderson under the auspices of the Department of Research and Specialist Service. This station was closed down in 1973 and a new station was built in 1970–71 at Lake McIlwaine. Other similar stations were later established by the Department of Natural Parks and Wildlife at sites on Lake Kyle, in Inyanga and the Matapos (Bell-Cross, 1976).

Numerous species of fish were introduced between 1910 and 1960 (listed in Balarin, 1984). These include a large number of fish introduced by angling societies and maintained in private and Government hatcheries. A number of hatcheries are still functional. Some fish species have now become well established in natural waterways creating an important fishery.

Rainbow trout (Salmo gairdneri), originally from the UK and trans-shipped via South Africa, was introduced for angling purposes, later to develop into a commercial aquaculture operation. Today, trout are extensively farmed in cages in private dams above the altitude of 1 000 m.

Table 2. SELECTED MORPHOLOGICAL DATA AND USE OF ZIMBABWE RESERVOIRS
(Numbers refer to Figure 2)
(from Thornton, 1980)

^a c=commercial/industrial
f=major fishery (over 100 t/yr)
i=irrigation
p=power generation
r=recreation
w=water supply

Fig. 2. LOCATIONS OF THE MAJOR DAMS
(Thornton, 1980)

A Zambesi River Mana Pools
B Sabi River Sabi (Chipinga)
C Lundi River Chipinda Pools
D Nuanetsi River Domisa
E Limpopo River Sengwe (Pafuri)

Fig. 3. FLOODPLAINS AND THEIR LOCATIONS IN ZIMBABWE
(after Thornton, 1980)

The present estimate of aquaculture production is 800 t/yr (Van der Lingen, pers.comm.), but this is possibly inclusive of a large number of small commercially operated farm dams. As with the fishery, there would appear to be a paucity of data on the actual extent of fish farming.

Vincke (1989, pers.comm.) detailed aquaculture production in Zimbabwe from 1982 to 1987 as follows:

Table 3. AQUACULTURE PRODUCTION (t) - Zimbabwe, 1982–1987

Recent publicity and local promotion of the development of a freshwater prawn farm at Kariba has spurred a renewed interest in commercial farming. Were the present interest developed to its full potential, over 2 000–2 500 tons of fish could be produced yearly (Balarin, 1982a).

3.2 Fish production and per caput supply

Table 4. FISH PRODUCTION AND PER CAPUT SUPPLY - Zimbabwe, 1970–1987

¹ Source: FAO
² Source: FAO Fisheries Department FISHDAB
³ included in “Inland capture” if not specified
⁴ - = data not available
⁵ Vincke, 1989 (pers.comm.)
⁶ rough estimates from 1970 to 1976

3.3 Inland catch range and potential yield

Table 5. INLAND CATCH RANGE AND POTENTIAL YIELD

¹ Sources: see text
² All reservoirs excluding Kariba, Kyle, McIlwaine and Robertson

4. STATE OF THE FISHERY (adapted mainly from Balarin, 1984)

4.1 Yield

Apart from the accurate records kept of the Lake Kariba Fishery and those of the lakes where National Parks have a station, there appears to be little or no statistical information of the extent of fishing in other Zimbabwean waters. A recent review by Kenmuir (1982) is perhaps the most up-to-date estimate of the fishery potential.

In essence, the fishery can be divided into Lake Kariba (the main catch) and the rest. Fishing is mainly practised by commercial companies and by subsistence angling and artisanal fishermen. An unknown element of illegal fishing has also to be considered.

4.2 Factors influencing yield

In the Kariba Reservoir, the sardine fishery has remained restricted to the requirement for capital-intensive operations by virtue of the behaviour pattern of fish. Small-scale artisanal fishery development is not considered feasible (Marshall, 1982), although there have been recent attempts at development.

4.3 Future development possibilities

Kenmuir (1980) presents a conservative estimate of fish production potential of all water resources (excluding aquaculture) in Zimbabwe at 26 000 t/yr. If Marshall's (1982) estimates of sardine fishery potential of Lake Kariba and others are included, it can be said that Zimbabwe has an annual potential of from 21 000 to 44 000 tons. A more realistic value, however, may be around 28 200 t/yr. This does not include the shellfish potential of Lake Kariba and Lake McIlwaine, estimated at a further 12 000 t/yr (Kenmuir, 1980).

The fact remains that there is no definite estimate of the actual fishery resources of Zimbabwe's 300 000 ha of fishable waters.

Pond culture is also likely to increase in the future, with a potential development being estimated as 2 000–2 500 t/yr (Balarin, 1982b).

5. KEY BIBLIOGRAPHY

Balarin, 1984

6. WATER BODIES DIRECTORY

BUZI RIVER
(International water)

LIMPOPO RIVER
(International water)

PUNGOE RIVER
(International water)

SAVE/SABI RIVER
(International water)

ZAMBEZI RIVER
(International water)

AMAPONGOKWE RESERVOIR

Fig. 4. RIVERS AND LAKES OF THE ZAMBEZI
(Welcomme, 1972)

BANGALA RESERVOIR

INGWEZI RESERVOIR

KARIBA RESERVOIR
(International water)

Fig. 5. LAKE KARIBA
(Welcomme, 1972)

KYLE RESERVOIR

LESAPI RESERVOIR

MAITENGWE RESERVOIR

MANJIRENJI RESERVOIR

MAYFAIR RESERVOIR

MAZOE RESERVOIR

McILWAINE RESERVOIR

Fisheries data
No. of fish species: 26 (including 5 introductions)
Total annual catch:

* commercial fishery only
** all fisheries (commercial, subsistence angling and illegal beach seining)

Potential annual yield: 300 t (Marshall, 1982)

NGESI RESERVOIR

PALAWAN RESERVOIR

ROBERTSON (= DARWENDALE) RESERVOIR

RUTI RESERVOIR

SEBAKWE RESERVOIR

SIYA RESERVOIR

UMSHANDIGE RESERVOIR

UPPER NOEMA RESERVOIR

OTHER RESERVOIRS AND WATERWAYS

Under “Other Reservoirs” are included all reservoirs except the four major reservoirs (Kariba, Kyle, McIlwaine and Robertson).
Table 6 gives the available main characteristics.

Table 6. CHARACTERISTICS OF OTHER RESERVOIRS AND WATERWAYS IN ZIMBABWE
(adapted from Balarin, 1984)

^a Kenmuir, 1981b, 1982
^b Grizic, 1980
^c Bowmaker, 1975
^d Junor, 1981

The 8 000 small reservoirs (less than 13 ha) in Zimbabwe have a total area of 21–45 000 ha (Kenmuir, 1981b). The same study undertook a census of subsistence angling and obtained a value of 300 g/ha. This gave a possible yield of 270–390 kg/ha/yr and a potential harvest of 4 200–7 200 t/yr. Kenmuir (1982) adopted 6 000 t/yr as a theoretical maximum and estimated the 1980 catches at 4 000 t/yr (cited in Balarin, 1984).

7. BIBLIOGRAPHY

Balarin, 1982a, b; 1984
Bell-Cross, 1976
Bowmaker, 1975
Cayron & De Fooz, 1981
Coche, 1968; 1969
Entz, 1984
Grizic, 1980
Harding, 1961
Jackson, 1971
Jubb, 1961
Junor, 1981
Kapetsky & Petr, 1984
Kenmuir, 1980; 1981a,b; 1982
LKFRI, 1981
Marshall, 1982; 1984a,b,c
Mitchell, 1977
SADCC, 1984
Thornton, 1980
Van der Lingen, 1981a, b
Welcomme, 1972