Africa: Widespread water surplus will persist in Botswana

18 February2021

THE BIG PICTURE
The 12-month forecast through October 2021 indicates intense water deficits across North Africa including widespread exceptional anomalies. Pockets of mixed conditions are also forecast (pink/purple).

Surpluses of varying intensity are expected across the Sahel, dipping into northern Nigeria, and in Eritrea and northeastern and central Ethiopia. Surpluses will be extreme to exceptional in central Mali, central Chad, southern Sudan, and northeastern Ethiopia. In Africa’s Horn, surpluses will be exceptional in the Nugaal region of northern Somalia though transitional conditions are also expected. Deficits are forecast in Somaliland.

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Moderate deficits are forecast in Sierra Leone, severe deficits in southeastern Nigeria, extreme deficits in southern Cameroon, and exceptional deficits in Equatorial Guinea and southwestern Gabon. Other regions with a forecast of deficit include the central Congo River Basin in Democratic Republic of the Congo, northern Angola, northeastern Mozambique, southern Madagascar, and Eswatini (Swaziland) and the Upper Vaal River region nearby in South Africa. Anomalies will be exceptional in north-central Angola, Mozambique, the Lower Tsiribihina River region in Madagascar, and the Upper Vaal River region.

In East Africa, surpluses are forecast in Tanzania, and will be extreme between the Gombe and Shama Rivers and severe surrounding Dodoma. Surpluses are also expected from western Kenya into Uganda, along the Victoria Nile through Uganda, and in South Sudan. Severe to extreme surpluses will dominate much of Botswana and through central Namibia to the coast. Surpluses are expected on the Molopo River in southern Botswana and the Auob River in Namibia. Much of southern Mozambique will see surplus conditions as will southern Zambia. Other areas with a forecast of surplus include Malawi; northwestern Madagascar; several pockets of South Africa in Western, Eastern, and Northern Cape; the region east of Kinshasa in Democratic Republic of the Congo; and northeastern Gabon.

FORECAST BREAKDOWN
The 3-month maps (below) show the evolving conditions in greater detail.

The forecast through April 2021 indicates that deficits in Africa will shrink and downgrade. Deficits in North Africa will be moderate overall though exceptional anomalies will span the shared northern border of Algeria and Libya and form a band in central Sudan. Transitional conditions are expected in the western Sahel but surpluses in the east will remain intense with exceptional anomalies increasing in southern Chad. Exceptional surpluses are expected to re-emerge at the intersection of Guinea, Mali, and Côte d’Ivoire. Surpluses are also forecast in southern Liberia, eastern Burkina Faso, and western Central African Republic and its northern tip. Exceptional surpluses will re-emerge in the Nugaal Region of Somalia. Deficits of varying intensity are forecast for southeastern Nigeria, central Cameroon, Equatorial Guinea, northern Democratic Republic of the Congo, northern Angola, Eswatini and the Upper Vaal River region in South Africa, and southeastern Madagascar.

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From May through July 2021, moderate deficits are forecast across the Sahara with some more intense pockets including in western Algeria and northern Niger. In the Sahel, surpluses will re-emerge in the west and persist in the east. Surpluses will persist in Somalia’s Nugaal region and will emerge in the Ethiopian Highlands and Eritrea. Deficits will nearly disappear around the Gulf of Guinea and central and southern Africa, with moderate anomalies persisting in northwestern Angola, Eswatini, and the Upper Vaal. Surpluses will shrink in East Africa persisting primarily in central Tanzania but will remain widespread in Botswana and into its neighbors, particularly Namibia. Pockets will persist in southern Mozambique.

The forecast for the final quarter – August through October 2021 – indicates conditions similar to the forecast for the prior three months.

Please note that WSIM forecast skill declines with longer lead times.

IMPACTS
Flash flooding after heavy rainfall claimed 28 lives in Tangier, Morocco in early February, many of whom may have died from electrocution in the basement of an illicit textile factory.

The floodgates of the Vaal Dam near Johannesburg, South Africa were opened on 11 February after days of heavy rain, and a day later Nandoni Dam in Limpopo Province to the north breached its capacity. Ten fatalities were reported in Limpopo as of mid-February.

For the first time since opening 20 years ago, the Afriski Resort in the Maluti Mountains of Lesotho flooded after receiving 60 mm of rainfall (2.36 inches) in half an hour). Damage to roads, buildings, and other infrastructure is estimated to be millions of rands. Since December of 2020, the mountain region has received 800 mm (31.5 inches) of rainfall, twice that of last year.

Namibia is experiencing its wettest rainy season in 20 years. January 2021 rainfall in Windhoek, the nation’s capital, totaled 228 mm (9 inches) compared to the long-term average of 85 mm (3 inches), as evidenced in the natural-color and NDVI (Normalized Difference Vegetation Index) images from NASA.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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