COMMENT RODGER BOSCH/AFP/GETTY The narrow body of water that remained at South Africa’s Theewaterskloof Dam in May 2017. Lessons from Cape Town’s drought Don’t blame climate change. People and poor planning are behind most urban water shortages, argues Mike Muller. ince May, winter rains have brought a looked set to be a long, hot summer, people received water for only two days a week. reprieve to the citizens of Cape Town, began to panic. Once the city’s reservoirs had been drained South Africa. The city had endured Municipal authorities told residents of clean water, the utility firm pumped and Ssevere drought for three years. Concerns that to slash their water consumption. For treated the polluted water that remained. In its water supply might run out in the summer suburban households, that meant going 2008, Barcelona in Spain had to ship water have been set aside, hopefully, for another from pre-drought usage of around 200 litres in from Marseille, France. During its dec- year. But the city remains vulnerable. per person per day to 50 litres per person ade-long ‘millennium drought’ in the 2000s, The situation was very different in 2013. per day (picture a bathtub filled to less than Australia spent billions of dollars on desali- Then, Cape Town had one of its highest 10 centimetres). Although many of their nation plants, most of which have not been annual rainfalls in decades. Reservoirs poorer compatriots regularly live with such used since. brimmed, and officials declared there was no a supply, suburbanites suddenly had to give It is important to learn from the experi- need to increase supplies before the 2020s. up their gardens and collect shower water to ences of Cape Town and elsewhere. Urban After another wet winter in 2014, the 6 main flush their toilets. The city more than halved growth means that many more places will reservoirs that feed the city were 97% full. its overall use, to just over 500 million litres face similar challenges as they compete with Then the drought began. Reservoir levels a day, and avoided ‘day zero’. surrounding regions for water. Big cities fell to 71% in 2015 and to 60% in 2016 (see Cape Town is one of several cities to see need to begin informed long-range planning ‘Cape Town drought’). When they reached its water supply fail in the past decade. In and to focus on minimizing risks from cur- 38% in 2017, at the beginning of what 2014 and 2015, parts of São Paulo in Brazil rent climate variability. Climate change adds 174 | NATURE | VOL 559 | 12 JULY 2018 ©2018 Spri nger Nature Li mited. All ri ghts reserved. ©2018 Spri nger Nature Li mited. All ri ghts reserved. COMMENT to the uncertainties. Shortages attributed to extreme weather or to global warming are CAPE TOWN DROUGHT still more often due to poor management. Lower than average rainfall in South Africa’s Western Cape exacerbated water shortages over the past 3 years. People’s beliefs and behaviour are as much The total amount of water stored in the six largest reservoirs that supply Cape Town fell to new lows each year. a part of the systems to be managed as are ANNUAL RAINFALL JULY 2016 TO JUNE 2017 pipes, pumps and the environment. Rainfall (% of normal*) SHORT-SIGHTED 0–50 Cape Town’s problems are due in large part 50–75 BOTSWANA to a turn away from management based on 75–100 100–150 SOURCE: CLIMATE SYSTEMS ANALYSIS GROUP ANALYSIS SYSTEMS SOURCE: CLIMATE science and risk assessment towards a more 150–200 1 Pretoria populist approach . Johannesburg Since the 1980s, South Africa’s major con- urbations have used systems models to guide NAMIBIA their water management2. These models, run by the national government, are considered world-class. They map links between river SOUTH AFRICA LESOTHO basins, reservoirs and transmission channels Durban and use historical hydrological data to pre- dict probable stream flows. Those are then matched to projections of demand to assess how much storage is needed. The models Catchment area of AFRICA support real-time operations of the water urban water supply network as well as planning for develop- Cape Town ment. Crucially, they allow planners to assess Port Elizabeth risks of supply failures to different catego- ries of users and evaluate the effectiveness REGIONAL RESERVOIR LEVELS of responses such as restrictions. For two decades, policymakers heeded the 100 models. They guided managers, for example, Reduced urban consumption on when and where to tap sources and build 80 since early 2018 prevented reservoirs to enable the Western Cape Water water from running out. Supply System (WCWSS) to meet rising 60 demand from urban and industrial growth. But dam building stalled in the 2000s, 40 when local environmentalists campaigned (%) stored Water to switch the focus to water conservation 20 and management of demand. Such oppo- sition delayed the completion of the Berg 0 River Dam by six years. Eventually finished 2014 2015 2016 2017 2018 in 2009, the dam helped to keep the taps run- * Average for 1981 to 2010 ning in Cape Town this summer. Back in 2009, the models had already flagged a need to boost Cape Town’s water had not addressed the risk of such a severe implications of their decisions. supplies after 2015, but officials dismissed dry spell because “it is not practical to ring- They do now. So far, direct costs of the the recommendations. They were happy fence billions of rand for the possibility of a water crisis — reduced water revenue, to delay big capital investments and spend drought that might not come to pass”. losses in agricultural jobs and production the money elsewhere. They missed that the Then the worst case happened — a very and indirect costs such as a drop in tour- Cape’s wine and fruit farmers (who are enti- dry 2017. How dry is disputed. Rainfall and ism — have come to more than 2.5 billion tled to one-third of the region’s water) were stream flows vary dramatically from place South African rands (US$181 million). not drawing their full allocation during the to place and year to year across the region’s Water tariffs for consumers have been rainy years and, like the city’s gardeners, mountainous terrain. At the Jonkershoek raised by 26% this year. Yet, investing 1 bil- were using more in drier years. weather station, which is close to the catch- lion rands in infrastructure in 2013–14 The response was short-sighted. The 6 ment of the two largest dams, rainfall varied: would have cost just 75 million rands per Western Cape reservoirs that feed the city 1,250 millimetres in 2013; 900 millimetres year in interest charges — that would have hold less than 2 years’ supply: 890 million in 2014; less than 500 millimetres in 2015; been cheap insurance, even if it had proved cubic metres, compared with a reliable 750 millimetres in 2016; and 700 millimetres unnecessary. annual yield of 570 million cubic metres. It in 2017. In 2017, flows in a small, undevel- Cape Town’s decision-makers have tried took two successive dry winters, in 2015 and oped stream in the same area were just 20% to shift the blame, with climate change an 2016, for the municipality to realize that it of what they were in 2013. obvious target. Helen Zille, premier of the was in trouble. City leaders banned water use Three consecutive dry years have Western Cape, wrote last October that “the in gardens and car washing, and promoted occurred before, in the late 1930s and from impact of climate change is probably the conservation, water-efficient appliances and 1970. Three dry years in 2002, 2003 and 2005 reason that climate cycles have become so higher tariffs. were fortunately interrupted by a wet 2004. unpredictable”. Yet there is little evidence of They defended their decisions. The coun- These risks were reflected in the hydro- a departure from normal variability in the cillor responsible for water services, Xanthea logical models. But Cape Town’s leaders did catchments. Although data from outside Limberg, wrote in April last year that they not comprehend the social and financial sites are cited to support climate-change ©2018 Spri nger Nature Li mited. All ri ghts reserved. ©2018 Spri nger Nature Li mited. All ri ghts reserved. 12 JULY 2018 | VOL 559 | NATURE | 175 COMMENT implementing strong centralized systems such as China’s, improving cooperation between the various organizations involved might help7. Because rivers generally cross political boundaries, water management is often organized in ‘watersheds’ that can be distant from politicians and their citizens. Cape Town draws water from two rivers beyond its boundaries, each of which is man- aged by a different agency. Managing water in SWIEGERS/BLOOMBERG/GETTY WALDO ‘problem-sheds’ that encompass major water users and the geographical areas on which they depend would be a better approach8. As water needs grow and water systems evolve, more resources will need to be devoted to monitoring and modelling. Tech- nical guidance must be integrated into politi- cal processes. As a minimum, politicians need to know who is doing the modelling and what the recommendations are. They also need that information in a for- mat and language that empowers them to act appropriately. So hydrologists must col- Residents fill water containers at the Newlands natural-water spring in Cape Town in November 2017. laborate with experts from the social sciences and humanities, notably economics, policy theories, it was the three-year sequence of transfers because of a manifesto commit- and law, to develop water-management tools dry years that proved devastating.