Fears of drought escalate
04 January 2019 | Weather
Recent downpours in many parts of Namibia and a trickle inflow into dams in the central areas have raised hopes of a good rainy season but experts warn that farmers should rather prepare for drought than pin their hopes on good rainfall for the rest of the season.
South African climatologist Johan van den Berg, a climate scientist at Santam Agriculture, said this week that from an agricultural viewpoint, the rest of the 2018/19 summer season carries a high risk of drought conditions.
He stressed however that a notable challenge climate experts are wrestling with currently is the fact that accurate weather forecasts are highly unreliable and difficult.
“The 2018/19 summer season will more than likely be remembered as one of the most difficult forecasting seasons in many years. Few if any weather outlooks forecast that the first part of the season would be so dry,” he said.
Van den Berg added that southern Africa is more than likely nearing the end of a drought cycle that started in 2012, based on a long-term overview.
“It is very likely that wetter conditions will set within the next year or two. The challenge is to survive the current season.”
As a result of the forecasting difficulties, which are due to several factors, while it is recommended to prepare for dry months ahead, “there is always a chance that the rain conditions could improve.”
To guard against false optimism and to ensure adequate planning, however, Van den Berg said it was crucial that farmers ensured they were ready for a potential disaster in terms of rainfall. “Should it turn out differently, [they should] see that as a bonus and not the other way around.”
In August last year already the consensus reached by climate scientists for the southern African region was to expect erratic rainfall and normal to below-normal rainfall for the period October 2018 to March 2019.
The most recent weekly dam bulletin issued by NamWater shows that the level of the Von Bach Dam rose from 39.7% to 41.5% by 31 December as a result good rains.
The Omatako Dam’s level has increased slightly from 0% to 0.5% since last week.
The level of the Swakoppoort Dam continued to drop in the last week of 2018, from 23.9% to 23.5% by 31 December.
Compared to last year, the dam levels are worrying.
At the same time last year, the Swakoppoort Dam was 40.8% full and Von Bach 60.3%.
The level of the Omatako Dam is the same as last year – empty.
In August, the City of Windhoek announced an emergency water supply strategy, in addition to new mandatory 10% water savings, to ensure sustainable and secure water supply under drought conditions.
Currently, Windhoek's southern suburbs are primarily supplied with water from nine boreholes that were drilled in the aquifer, the city’s emergency resource, over the past year.
At least 20 000 cubic metres of water is extracted daily from the aquifer.
This supply strategy was designed to address the lack of inflow to the three main supply dams - Von Bach, Swakoppoort and Omatako - whose supply to the city was halved from around 60 000 cubic metres daily to 30 000.
The city’s water supply is additionally supplemented with around 17 000 cubic metres a day from the Windhoek reclamation plant, which is the maximum output it can provide.
Yet, in order to ensure the new daily usage target of 67 000 cubic metres a day is achieved, a 10% saving by residents is crucial.
Koos Theron of the City of Windhoek's infrastructure, water, and technical services division explained at the time that the current water supply strategy is highly risky as it relies on the aquifer, which is a designated emergency resource.
He explained that the current daily abstraction of around 20 000 cubic metres is not sustainable in the long run, based on the average natural recharge of the underground water source which amounts to around 1.7 million cubic metres per year.
At the current rate, around 7.5 million cubic metres per year are being extracted, almost 4.5 times the recharge rate.
“If everybody can contribute, we should be able to get to the 67 000 cubic metres a day. If we do not, we have to exploit the boreholes further, which is not a good option, because we are already using our 'retirement money',” he said.