Threat of impending drought is real
Keto Segwai | Monday October 9, 2023 06:00
MAUN: Normal to below-normal precipitation is expected to negatively impact the first half start of the 2023-24 agricultural season from October to December 2023.
The forecast came out of a statement, released by the 27th Southern Africa Regional Climate Outlook Forum (SARCOF-27) conference that concluded last Thursday (September 28) in Mauritius. The forum normally releases its outlook on August 31.
The SARCOF-27 statement confirms that of Botswana’s Department of Meteorological Services (DMS), which was released on August 31 that cautioned of El Niño-driven conditions.
The forum forecast that for most of the period October to December (OND) most parts of the SADC region is likely to receive normal to below-normal rainfall.
According to the forum, the only exception will be north-western part of Angola, much of Democratic Republic of Congo, southern half of Tanzania, north-eastern Zambia, northern Malawi, northern Mozambique, Comoros, eastern Madagascar and Mauritius where normal to above-normal rains are expected.
The northern half of Tanzania and Seychelles are likely to receive above normal rainfall during this period of the 2023-24 season.
In its area-specific forecast, the DMS said that during the OND period normal to below-normal rainfall is likely to be experienced in Ngamiland, Chobe, Ghanzi and Kgalagadi while the eastern half of the country that include Northeast, Central, Southeast, Kgatleng, Kweneng and Southern districts are likely to get below normal rainfall.
The DMS explained that in the case of Botswana during the OND period, normal rain ranges from 50mm over Kgalagadi and 200mm over Chobe; while over Southern district is 120mm and 180mm over Northeast.
Over the OND period, temperatures are expected to be normal to above-normal
Though the period January-February-March (JFM) seem to bring some cheer to some parts of the Botswana and the region due to expected normal to above-normal rainfall, other places are likely to be worse off.
The areas that are likely to receive below-normal rainfall include the extreme eastern part of Botswana (North East and South Central), south-western fringes of Namibia, south-western South Africa, southern part of Zimbabwe, northern South Africa, Eswatini, southern Mozambique, and southernmost Madagascar. Seychelles is likely to receive above-normal rainfall during this period.
These below-normal conditions are expected to impact negatively on the maize triangle of South Africa resulting in below-average harvest. However, the expected cumulative average to above-average conditions in northern Malawi, northern Mozambique, and northern Madagascar are likely to support crop growth.
According to DMS report, the areas that are expected to receive normal to above-normal rains in the second part of the rainy season (January-February-March) are Ngamiland, North Central, Chobe, Ghanzi, Kgalagadi, Southern, Kgatleng and Kweneng.
During the JFM period, normal rain ranges from 120mm over Kgalagadi to 320mm over Chobe; while over Southern district it is 180mm and 220mm over Northeast.
The temperatures are expected to be above normal. Normal temperatures range from 30 C in the east and 34 C in the north and west.
The anticipated drought could be devastating to the country’s water supply system as most of the higher-capacity dams are located in the earmarked area – eastern Botswana. And these includes Dikgatlhong with capacity of 400 Mm3; Letsibogo (100 Mm3); Thune (90 Mm3); Shashe (85.0 Mm3); Lotsane (42.35 Mm3); and Ntimbale (26.5 Mm3).
The imminent drought spell could however be mitigated by the status of the dams. As of September 25, 2023, Water Utilities Corporation (WUC) estimated that of the country’s 10 dams only two (Bokaa and Nnyane) had supply falling below 12 months.
Otherwise the rest of the dams have enough supply to cover more than 12 months without water inflow. Dikgatlhong stood at water supply to cover 24 months; Letsibogo (18); Molatedi-South Africa (56); Gaborone (21); Thune (39); Shashe (20); Ntimbale (15); and Lotsane (17).
The situation could be dire though, should the El Nino conditions persist into the 2024/25 rainy season.
Similarly, such condition could also adversely affect the Okavango Delta and its tributaries that sustain the tourism sector and supplies most of Ngamiland with water and other aquatic resources.
This is particularly so as the Okavango Delta has experienced hydrological drought in the past two flooding seasons. Though the flood has come through this year, it is inadequate.
The forecast 2023-24 drought could also affect the source of the delta waters – the Angolan Highlands Water Tower. According to SARCOF statement, during the October-November-December season that water shed region is likely to receive normal to below-normal rainfall; while in the January-February-March 2024 it is expected to be normal to above-normal.
The delta is only considered well-replenished in the event of a combination of equally good rains in the Angolan water tower and good localised rains in the delta itself.
Such a combination ensures all the Okavango River tributaries are well replenished, including the bird and fisher’s haven Lake Ngami and Lake Xau.
Due to the previous hydrological droughts Nhabe and Kunyere Rivers that feed into Lake Ngami have not received adequate water.
Without the water from the river, the WUC struggles to provide Maun residents with water.