Visualizing South Africa’s Drought

10/27/16
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Every year, South Africa yields one of the largest agricultural harvests on the African continent, producing megatonnes of both staple cereals as well as valuable export products like citrus and wines.  However, the worst drought in a century, now in its second year, has wreaked havoc on production and driven up food prices across the region. South Africa is expected to import more than 2 million tonnes of maize in 2016/2017 to make up for the shortfall in domestic production of the crop, which is its most important staple food.[1]

On Monday, Reuters reported that farmers are poised to bet big that the rains will come back, planting hundreds of thousands more hectares of maize this season in an attempt to reach pre-drought production levels.[2]  Will the bet pay off?

The South African Context

South Africa is a relatively water scarce country; its agriculture sector depends in part on a reliable supply of irrigation water from catchment areas upland. About 60% of the country’s water supply goes to the 25-30% of agricultural production that is irrigated.[3]  Much like in other nations, irrigated agriculture accounts for some of the most valuable production, such as the export-oriented citrus industry. While irrigation reservoirs would normally supplement deficient rainfall, the long running drought has run water levels in the catchment areas to their lowest levels in decades.

 

Meanwhile, the water needs of the South African people are increasing, due to both absolute population growth and relative increases in per capita water consumption, a result of economic development. Currently, South Africa imports water from neighboring Lesotho (also drought-afflicted) to meet its requirements.[4]  Caught between dwindling supply and growing demand, the government has mandated cuts in both agricultural and municipal water use.[5]

The Drought

Using aWhere’s database of observed weather, we can examine a profile of South Africa’s current drought situation. The graphic below displays the ratio of 2016’s recorded rainfall against the 10-year long-term normal rainfall. For reference, South Africa’s maize production region is outlined in black and occupies the eastern portion of the country.

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Figure 1: Long-term normal (LTN) is defined as the 10-year average precipitation. Precipitation data is daily, and is aggregated over the time period in each image to display to difference as a percent deviation from these norms.

The data shows a stark picture of the ongoing drought.  Large parts of the country continue to experience significantly less rainfall than normal. The high-producing northern areas in Mpumalanga and North West provinces have seen some of the most severe and widespread dry conditions.

Just as notable as the large drought areas is the extreme divergence from the norms in both directions - the vast majority of the land area is either much wetter or drier than normal. The graphic below shows an example of this aberration in the maize-growing area, with 9% of land area receiving ≥75% more rainfall than is normal, and 16% of land area receiving ≥75% less.

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Figure 2: Bars signify the count of aWhere virtual weather stations in South Africa, based on their 2016 rainfall difference from the long-term average.

The displayed data covers the September period in which summer rains typically begin, and yet roughly half of the maize-growing land area in South Africa was experiencing below half of its normal rainfall. This volatility in rainfall is an expected impact of climate change, and is a threat to agriculture, as most crops do not respond well to extreme variation in the environment. Maize requires healthy and relatively consistent rainfall during and immediately after planting but does not respond well to excessive rain leading to waterlogged soils.

Prospects for a Better Season

A comparison of total rainfall in the past month compared to rainfall in 2015 gives reason to hope for improvement. Rainfall across most of the maize-growing area was up significantly compared to last year’s record lows, a sign that the drought may be easing where maize farmers need it most.

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Figure 3: Comparing this year's rainfall to last year provides some room for optimism.  There has been more precipitation over the last month than in the year prior for many parts of South Africa.

However, the rainfall was far from enough to replenish supplies in the catchment areas and authorities have not backed off from the calls to cut agricultural and municipal water use.[6]  For a good crop to take root, the rains will need to continue into the crucial maize planting months of November and December.

South African farmers’ plans to invest heavily in maize planting reflect a growing optimism for an end to the drought. South Africa’s Crop Estimates Committee (CEC) on Wednesday issued a planting forecast that expected the largest increase in planting - 43% - to come in white maize, the variety intended for human consumption.[7]  And the national weather service has issued a forecast for likely higher rainfall due to a La Niña weather pattern in the coming months.  The stability and affordability of the average South African’s diet will depend on the next several weeks of rain. If the forecasted La Niña pattern does not come, South Africans will be feeling the effects long into 2017.

 

[1] http://af.reuters.com/article/investingNews/idAFKCN12Q1KF

[2] http://www.reuters.com/article/us-safrica-maize-poll-idUSKCN12O1IB

[3] https://www.dwa.gov.za/io/Docs/CMA/CMA%20GB%20Training%20Manuals/gbtrainingmanualchapter1.pdf

[4] http://mg.co.za/article/2016-09-28-00-south-africas-thirst-is-emptying-a-lesotho-dam-leaving-the-locals-parched

[5] http://www.bloomberg.com/news/articles/2016-10-06/-catastrophe-seen-by-s-african-agriculture-if-drought-persists

[6] http://www.timeslive.co.za/sundaytimes/stnews/2016/10/19/Dry-South-Africans-celebrate-insignificant-rainfall

[7] http://www.sagis.org.za/cec_reports_2016.html

Topics: El Nino, Big Data, Drought, Maize, South Africa

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