Cape Town Water Crisis Highlights a Worldwide Problem
The water supply is running dry in Cape Town, South Africa. The city’s reservoirs are shrinking as a three-year drought wears on. If it doesn’t rain soon, the drought could bring South Africa’s second most populous city to its knees.
Cape Town residents are adapting as best they can. They are skipping showers and finding new ways to conserve and reuse their meager allowance of 50 liters (13 gallons) per person per day. That allowance may soon be cut in half, too.
As soon as April or May, Cape Town could reach “Day Zero,” when the city will shut off the taps in homes and businesses. Residents will need to line up at collection stations to gather their water rations. Only hospitals, schools, and other essential services would still receive piped water.
If things continue on in this way, Cape Town is in danger of becoming the world’s first major city to run entirely out of water. How can this happen in a city of four million residents? And what other cities may be at risk? Upmanu Lall, director of the Columbia Water Center, explains.
What went wrong?
Worldwide, people have designed water systems so that the amount of water they store and release is based on the worst drought they have seen in that region. The problem is that the estimate may only be based on 10, 20, or 40 years of data. It’s not enough. The variation and severity of droughts can vary somewhat cyclically, depending on El Niño and other longer-term cycles. Cape Town has seen three years which are some of the driest at least in the last 60 years, but if you look at the longer record, this is not altogether a big surprise. The 1940s had a comparable drought as measured by the total shortage relative to the target supply. There probably is some role of climate change, but that’s not what I see as the primary issue. It’s just that the management processes we have were designed with a limited understanding of how climate cycles are manifest.
Is there anything that Cape Town could have done differently?
Cape Town releases 550 million cubic meters of water a year, and their storage is 900 million. So even if it didn’t rain at all, they would have approximately two years’ worth of water stored. That’s not bad. But they waited too long before they decided they needed to act on the drought, and then their options were very limited. If you don’t realize that you’re in a drought, you run out a lot faster than if you start curtailing use the minute you start seeing the drought. Cape Town has been restricting water use for the last few months, but in the previous year they really didn’t reduce much.
What can be done now?
By and large, the people don’t have low-flow shower heads or toilets. Typically one flush takes 15 liters of water. The city has curtailed water use to 50 liters per person per day, ao that’s three flushes per day, total, and their showers probably also use around 15 liters per minute. People are essentially giving up on taking showers and baths because they can’t. They are capturing water out of sink when washing vegetables for cooking, for example, and putting that into the toilet for flushing. The fact that they are down to that level tells you that they’re pretty close to Day Zero.
The agricultural groups just recently decided to give up a bunch of their water. They’re sending about 10 billion liters of water from their reservoir to the Cape Town reservoirs so that the city can have it. This should push Day Zero out by a month or so.
I don’t think they’ll completely run out of water, because the government is spending a lot of money to bring in desalination units. These will use reverse osmosis. They will set up kiosks and deliver this water. I think in that mode, they’ll be able to deliver a fraction of the water they’re delivering now.
There are also systems for wastewater treatment and reuse. For Cape Town to build a plant and have it operational by May could be feasible on a small scale. But that can’t be the only water supply. You can imagine that if you’re reusing only 70 percent, then at the end of Day 1 you have 70 percent of your original water available. On Day 2 it’s 0.7 times 0.7, so you have only 49 percent available. Pretty soon, it basically takes you to zero.
Is there any way of avoiding Day Zero?
It could rain. South Africa is in its summer now, so they should start getting some systems with rainfall in the usual rainy season from April to September – but that is cutting it close if May is Day Zero. If they don’t get rain, then the reservoirs are finished. The city can always pipe water in from other places. The question is, what infrastructure are they planning to build and how fast they can build it? Or would they have to evacuate people out?
What other cities could face this type of situation?
Normally Cape Town would not have been at top of the list for consistent aridity. People talk about many of the cities in India and the Middle East as ones that would face this situation, but the per capita usage in many of those places is quite low as it is, and there’s a lot more use of groundwater. The places that are more vulnerable are places that think they’re doing a great job of managing their water supply and then they get a protracted drought. In the U.S., people normally talk about California as vulnerable. Texas has had significant droughts also. After the last major Texas drought, they started recycling and rainwater harvesting. In Florida, North and South Carolina and Georgia, their droughts are fairly significant.
Vulnerability is a function of climate, but it’s also as much a function of perception of the local water agency as to what their issues are and how they’re dealing with it.
How can we avoid water crises like Cape Town’s?
Because most water management plans are contingent on relatively short climate records, drought risk is most likely much higher than most people think. Most climate models aren’t good at reproducing the decade-long or century-long droughts that we’ve seen in the past.
With the America’s Water project, the Columbia Water Center has reconstructed water availability for the entire U.S. over the last 500 years. We’re using that to score the performance of different water management schemes across the country. We’re using it to develop strategic long-term planning for infrastructure.
New York City and other cities have drought plans, but they are based on relatively short records and they don’t look beyond their jurisdiction. When there’s a widespread drought, when there are problems which are beyond your jurisdiction and everybody in the region is suffering, the opportunities are much lower. For that level of drought in the U.S., we don’t really have a strategy at the moment. That’s why we’re working on the America’s Water project.
The main story here is that people are starting to come to grips with the fact that we need to do a better job at balancing water supply and demand.