Friday, 13 August 2021

Insights from studies of water shortages

Water shortages are increasingly common as an impact of climate change. Rainfall is not predictable, but most places have sufficient water reservoirs that shortages happen slowly and can be foreseen. At some point consumers are asked to be careful, and as disaster looms nearer these messages become increasingly frantic. Does this remind you of anything else? Climate change also happens slowly and not exactly predictably and exhortations to reduce emissions are becoming increasingly frantic.  Whether or not we will avert disaster remains to be seen. In this post I discuss insights from three journal article relating to damage limitation in drought. The first is about the near disaster in Cape Town during 2017/2018, from the view of the Cape Town water supply management. The second is also about Cape Town but from the view of residents – how the shortage affected different kinds of people. The third discusses how residents of Fortaleza (in Brazil) responded to increasing water prices during a drought. 

Richer households consume more water – but the difference varies.

There are inequalities in every city – but some are less equal than others. The chart below right shows water consumption in Fortaleza  by socioeconomic category. (I have merged A and B because there were so few.) The higher classes use more water, but not massively so. 

In these charts, the dashed line indicates 150 lpd which is the latest UK average (prior to the pandemic we used a little less, about 140). Data from [2] and [3]

In contrast, the difference in water use between classes in Cape Town (left) was massive. The management paper [1] is a bit vague on the subject: they say the average use (as of 2011) was 232 lpd (litres/person/day) and they also say 77% of householders had taps in the home, while 15% had taps in their yard – presumably then 8% had neither. The residents-view paper [2] is more explicit on the matter. They found consumption varying from 10 lpd in some informal settlements up to 800 lpd or more in elite districts. Considering all domestic consumption, informal districts accounted for 4% of water consumption while the middle and upper classes were responsible for 70%.

There are parallels with energy as richer households consume more energy too – which means they are more responsible for climate change. Considering energy in the UK, a UKERC briefing paper reports energy consumption (including energy embodied in goods and services) by income (for 2014) [4]. They found the median households consumed twice as much as the poorest and the richest 10% consumed five times as much. Most of the difference was in travel and imported goods.

Poorer households spend a higher proportion of their income on water.

Fortaleza residents were not very different in actual water consumption, but considering water bills as a fraction of income, this varied from less than 1% for the AB class up to 23% for class E.  There are similarities for energy in the UK too, with poorer households spending a relatively high proportion of their disposable income on fuel.

Increasing water (or road) supply increases demand – and inequality.

The Cape Town residents paper has some suggestions as to how efforts to improve water supply backfire and increase inequality. They cite ‘supply-demand cycles’. When there is a shortage, efforts are made to increase supply (such as building a new reservoir). This easing of the shortage increases demand – and the extra is taken up by the affluent who can most afford it. In the Cape Town case the least affluent hardly have access at all. 

I am reminded of the problem of road congestion.  Road congestion (cf water shortage) leads to building more roads (more reservoirs) which leads to more cars on the road (higher water demand). In addition, inequality increases as it is the richer classes that make most use of the extra road space. Two thirds of the poorest UK households do not even have a car [5].

Droughts happen slowly – but resilience varies.

Resilience to drought depends on the volume of stored supply versus demand. In the case of Brazil, the drought started in 2012 and punitive pricing was started in 2016. In Cape Town the drought started in 2015, restrictive measures started in 2016 and the mayor declared a state of disaster in 2017, when reservoir levels dropped to 20%. The last 10% is generally considered unusable so this meant there was only a few months of normal water use left [1]. 

It has since been estimated that the Cape Town drought was made three times more likely by climate change [2].

It was hard to get Cape Town leaders and officials to engage with the disaster plan.

Cape Town water management set  up a ‘Water Resilience Task Team’ to prepare a disaster plan. This came in two phases: preservation restrictions, to ensure supply and ‘disaster restrictions’ which involved turning off the mains and supplying water from distribution points through the city. Phase 1 involved restricting supply to 50 lpd while Phase 2 would be just 25. Planning for phase 2 was difficult because it was difficult to contemplate such a severe disaster: Phase 2 planning, was challenging because officials believed that the likelihood of needing to implement the plans was very low …  After the Disaster Plan was conceptualised, it was clear that Phase 2 would be very disruptive and without a pre-agreed trigger point, it would be too tempting for decision-makers to delay the decision to escalate from Phase 1 to 2 to mitigate social, economic and reputational fallout. This would put the City at greater risk of completely running out of water, effectively moving directly from Phase 1 to Phase 3, dramatically increasing the risk to residents. 

Ultimately, the trigger was set at a reservoir level of 13.5%, representing three months at the 50 l/person/day level. Fortunately, this level was never reached and phase 2 was not implemented.

Phase 1 implemented severe restrictions for households. Some farmers donated water.

Phase 1, however, was implemented in January 2018.  As well as the restrictions on domestic consumption, supplies to farmers for irrigation were restricted. Some farmers even donated water to the city, but these added up to just a few percent of usage. Additional supplies were also brought in from small scale desalination plants and boreholes.

During this phase, the restrictions achieve 70% drop in demand. 

Both places had supporting measures to ensure poorer households could afford water.

In normal times, both places have special measures to ensure that poorer households had access to sufficient water. In Cape Town – in normal times - every household is allowed 6000 litres/month of water free [2]. In Fortaleza the price a household pays for water increases with use. Up to 10,000 litres/month they pay the lowest price.  At more than 20,000 litres/month the price is tripled [3]. 6000 litres/month is enough for 100 lpd for 2 people. However, households in Cape Town are often a lot bigger than that. 

In Cape Town, some of this support was removed.

In Cape Town, as the drought escalated, the free allocation was abolished and water tariffs increased. This was a big shock for many. Some of us is not privileged to have money every day to go buy water and then you need to manage your washing, water for your toilet, [...] or to clean the yard and everything. So, it was a lot of strain on us also. Some of us do not work, there is no income every day to go buy water and you need to travel to go buy water... Is not that you can just walk around the corner and go buy some water [2].

Impacts on poorer households were worse than intended.

During phase 2 household use was restricted to 350 litres/day which was meant to be enough for 6-7 people. However, houses in the townships often had up to 15 people from several families sharing [2]. These restrictions were enforced using water meters on each outlet. When the limit was reached, the flow stopped.

In Fortaleza, water supply for poorer households was protected.

In Fortaleza, the restrictions were less drastic. Each household was set a target to reduce use by 20% and any amount above this would be charged with a punitive tariff.  However, this did not apply to households using less than 10,000 litres/month. These were likely to be small households, or poorer households using less water[3].

In Cape Town, some well-off households drilled their own boreholes.

In the wealthier areas of Cape Town, households had a range of coping strategies.  They bought bottled water, some went outside the area to collect spring water and demand for rainwater tanks rose sharply. Some who were lucky enough to live over an aquifer even drilled their own boreholes. 

Publicity campaigns alone had some effect but not enough.

Prior to the punitive measures, there were publicity campaigns to encourage people to save water. In Fortaleza, judging from the charts in the articles, usage was down about 10% before the punitive measures were initiated. Also in Cape Town, peak demand in January 2016 was down about 10% from the year before, but that was already higher than the previous normal year, so overall there was no difference. In a drought year people do tend to use more water at home, at least they do in the UK. The extra is for things like more showers, watering the garden and filling paddling pools. In Cape Town many of the elite have swimming pools.

Pricing and physical restrictions were effective.

In Fortaleza, the target of 20% reduction for each household was achieved (on average), even though this was a soft limit, achieved by pricing rather than actually turning off the tap. In Cape Town, the reduction target was absolute rather than relative to the starting point and for an average household it was a reduction of nearly 80%. This was enforced – though some households got round it by other means. 

The level of pricing was not important. The signal was enough.

The surprising result of the pricing paper is that although the punitive pricing had the desired effect, this did not depend on the actual prices. The poorest households minimise their water consumption anyway, and the wealthiest households do not have to worry about the cost. However, the signal of having a price increase due to the drought was an important trigger for water saving practices.


This is quite a long post and I hope you have kept up with it. Here are the most important points, in my view, all of which have parallels for climate change. None of them are surprises but it does not hurt to reinforce things we know but sometimes forget.

  • Building new reservoirs to increase supply does not necessarily bring greater resilience to drought. Paradoxically it can reduce resilience, if demand is allowed to increase. Unfortunately increasing supply can trigger demand. So, for example, it is important not to increase capacity for cars on the road, at least until we ensure the new capacity is going to be low carbon. 
  • Poorer households are more vulnerable and need protection. In the Cape Town case, plans were based on assumptions of household size that were too low – this meant many vulnerable residents suffered greater restrictions than were intended. It is critical that climate change policy is evaluated carefully for impacts on poorer households.
  • Calls for voluntary restrictions on water use made a difference but not enough. Setting a punitive pricing signal was effective, but the actual level of increase is not so important as having an increase and explaining why it has happened. This has interesting implications for carbon taxes or pricing. Also, the idea of setting per-household targets related to previous use, and higher prices for going over the target, could conceivably be applied to the energy sector. However, transparency is key.
  • If you have sufficient resilience to start with and you take action early enough then you can get through your drought with less drastic restrictions on use. On climate change, we are clearly running out of resilience and time. Apparently we only have about 11.5 years now [6].
  • Officialdom finds it hard to plan for disaster in a timely fashion, especially if there is an excuse to think it unlikely to happen.  However, they can do it if they have to. There is hope for COP 26.

Postscript - Cape Town plans to diversify its water supply, increase recycling and adjust pricing.

Since the events described above, Cape Town has developed a new water resource management strategy [7]. Currently, 96% of their water is from rain-fed reservoir storage and the rest from groundwater. By 2040 they will have added further groundwater sources, and a desalination plant. The surface water proportion will then be only 75%.  Desalination costs three to five times as much as supply from the dams and will be used mainly when reservoir levels are low.

They also intend to increase waste water recycling. This works in two ways. Some industrial customers take waste water which has been treated but not to a potable standard. This means they need less of the mains water. Also some treated water is pumped into one of the water source aquifers, so the aquifer acts as an underground reservoir. They intend to expand both of these programmes. 

Finally, Cape Town is to have a new tariff structure. This will have three tiers with increasing prices for higher use, plus indigent' consumers will continue to receive a basic ration of free water. 

[1] Managing city-scale slow-onset disasters: Learning from Cape Town’s 2015–2018 drought disaster planning (Hugh D. Cole, Megan J. Cole, Kayleen J. Simpson, Nicholas P. Simpson , Gina Ziervogel, Mark G. New, International Journal of Disaster Risk Reduction) 2021

[2] Don’t blame the rain: Social power and the 2015–2017 drought in Cape Town (Elisa Savelli, Maria Rusca, Hanna Cloke and Giuliano Di Baldassarre, Journal of Hydrology) 2021

[3] A data-driven model to evaluate the medium-term effect of contingent pricing policies on residential water demand (Taís Maria Nunes Carvalho∗, Francisco de Assis de Souza Filho, Environmental Challenges) 2021

[4] Funding a Low Carbon Energy System: a fairer approach? (UKERC) 2018

[5] Percentage of households with cars by income group, tenure and household composition: Table A47 (ONS) 2020

[6]  In-depth Q&A: The IPCC’s sixth assessment report on climate science (Carbon brief) 2021

[7] Our Shared Water Future: Cape Town's Water Strategy (City of Cape Town) 2020 (?)

1 comment:

  1. In this country it isn't even a legal requirement to have a water meter. So the chances of implementing any policy other than standpipes is minimal. Water meters should be compulsory. Water, and energy, prices should be changed to (a) abolish standing charges and (b) make succeeding units more expensive. e.g. a free x units, then y units at 'cheap' rate, then more units at 'standard' rate, and the rest at 'luxury' rate.


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