Climate System Analysis Group at the University of Cape Town no relation drought
In mid-January 2018, previous Cape Town Mayor Patricia de Lille announced that the City would be forced to shut off most of the municipal water supply if conditions did not change. Level 7 water restrictions, "Day Zero", would be declared when the water level of the major dams supplying the City reached 13.5 percent. Municipal water supplies would largely be switched off, and residents would have to rely on 149 water collection points around the City to collect a daily ration of 25 litres of water per person. This would further affect Cape Town's economy, because employees would have to take time off from work to wait in line for water. Water supply would be maintained in the City's CBD, in informal settlements (where water is already collected from central locations) and to essential services such as hospitals. At the time of the announcement, "Day Zero" was projected to take place on 22 April 2018, but soon thereafter this was revised to 12 April. The "Day Zero" projections were based on the fortnightly changes in dam storage levels, assuming that the rates of decline would continue unchanged, with no further rainfall or change in water demand.Residential and agricultural water usage declined significantly under the new restrictions. This enabled the City to move the estimated "Day Zero" back in stages, and on 28 June "Day Zero" was postponed indefinitely.Good winter rains in 2018 resulted in dam levels rising, but the national Department of Water and Sanitation announced that bulk water restrictions would remain in place until levels reached 85 percent. In September, with dam levels close to 70 percent towards the end of the rainy season, the city reduced consumer water restrictions from level 6B to level 5. Dam levels peaked at 76 percent. In November, restrictions were reduced to Level 3, or 105 litres per person per day. Under Level 3 restrictions, municipal water may be used to water gardens at certain times, using a watering can or bucket but not a hose, to wash cars using a bucket, and to top up swimming pools as long as the pool is fitted with a cover to prevent evaporation.Causes
Severe drought
The immediate cause of the water crisis was the extreme drought from 2015–2017 that exceeded the planning norms of the Department of Water and Sanitation. Research on long-term weather data done by the Climate System Analysis Group at the University of Cape Town determined that the low rainfall between the years 2015 and 2017 was a very rare and extreme event. Decreasing rainfall trends are linked to broader changes in the atmospheric and oceanic circulation, including the poleward shift of the Southern Hemisphere moisture corridor between 2015–17, displacement of the jet-stream and an expansion of the semi-permanent South Atlantic high pressure system. 2017 was the driest year since 1933, and possibly earlier, since comparable data before 1933 was not available. It also found that a drought of this severity would statistically occur approximately once every 300 years.
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