Rainfall of up to 100mm is possible in parts of the summer rainfall region over the next two weeks, raising concern about dam levels, especially in areas that already experienced flooding earlier this month.
By Alani Janeke, senior journalist at African Farming and Landbouweekblad
Since 18 November, most of the summer rainfall region has received less rain. This has been welcomed by grain farmers in the middle of their planting season, as well as lucerne producers who need dry conditions to make hay.
The reduced rain has also slowed inflow into the Vaal Dam, which has dropped to 100%. The Bloemhof Dam was 105% full on 24 November after water was released from the Vaal Dam last week. Rain in the upper Orange River catchment has lifted the Gariep Dam to 99%, and it is expected to start overflowing on 27 November. Vanderkloof Dam is currently 91% full, but water is being released and levels should drop below 90% by the end of November, creating some buffer capacity.
“The levels of these dams are worrying,” says independent agricultural meteorologist Johan van den Berg. ‘Large-scale flooding could easily occur if further heavy rain falls.’
Up to 100mm of Rain Possible
Weather models indicate the possibility of heavy rain this week and next week in Mpumalanga, the eastern Free State, Gauteng, the eastern parts of North West, the southern parts of Limpopo, as well as KwaZulu-Natal and adjoining parts of the Eastern Cape.
“Rainfall totals of up to 100mm or more are possible from 25 November to around 3 December,” Van den Berg says. “The chances of further rain remain good for most of December, especially over the eastern half of the country.”
Although hailstorms occur regularly in parts of the summer rainfall region, insurers say the damage so far has not been catastrophic. Localised damage has occurred, however. In the eastern summer grain areas, the planting window is beginning to close, and some farmers cannot access their lands because the soil is simply too wet for machinery.
Also read: Continued heavy rain expected over parts of the country before month-end
Rain Could Spread Westwards
From the second week of December, rain may extend further west, although very heavy falls are not currently forecast. Table-grape farmers along the Lower Orange River are anxious about rain over the next six to eight weeks, which coincides with harvest time. If grapes are harvest-ready and become wet, the berries may split and be susceptible to mould and rot.
“There is a good chance of rain in the second and third week of December around Upington and nearby areas, and this could pose a significant risk of damage,” Van den Berg says.
Eastern Cape, Garden Route and Winter Rainfall Region
Some parts of the summer rainfall region remain very dry. Much of the Eastern Cape interior has not received rain for some time, and grazing conditions are deteriorating rapidly. The Garden Route, where both winter and summer rainfall can be limited, remains critically dry.
The chances of rain over the central and northern Eastern Cape improve around 28–29 November and again in the first week of December. There is also a chance of light rain between 26 November and the first week of December around George in the Garden Route, with frequent cloudy conditions expected.
“A total of about 20mm or slightly more is possible up to the first week of December,” Van den Berg says. “But weather models currently show a low chance of rain for the rest of December.”
For the broader winter rainfall region, very little or no rain is forecast for at least the next three weeks. “The strong easterly to south-easterly winds over large parts of the region during the past three weeks are also a sign that the summer rainfall pattern has now set in over the northern parts of the country.
“The fact that these winds are blowing strongly from the east suggests strengthening low-pressure systems over the western interior. Cold fronts are still moving across the country, but they are weak and pass through very quickly.”
Also read: Good news for farmers: Above-average summer rainfall expected
Very Hot Conditions Ahead
Very hot conditions are expected over parts of the Western and Northern Cape. “Dam levels in the province are dropping by about 2% per week, and many smaller dams are approaching critically low levels,” Van den Berg says.
Water restrictions remain in place in several areas, especially along the Garden Route.
Very high temperatures are expected over the western interior of the Northern Cape and the West Coast until the first week of December.
“On 25 November, maximum temperatures could exceed 40°C, reaching up to 42°C in Clanwilliam, 43°C in Citrusdal and 44°C in Vredendal. These extremely hot conditions may continue into the first week of December,” Van den Berg warns. “Very hot weather is also anticipated in the Winelands and parts of the Overberg, although temperatures there should start cooling during the first week of December.”
Across the rest of the summer rainfall region, especially the summer grain areas, temperatures are expected to be moderate to cool. With widespread cloudy conditions, crop growth may slow down.
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