Over the past two decades, more than 80 metropolitan cities across the world have faced severe water shortages due to droughts and unsustainable water use. Future projections are even more alarming, since urban water crises are expected to escalate and most heavily affect those who are socially, economically and politically disadvantaged. Here we show how social inequalities across different groups or individuals play a major role in the production and manifestation of such crises. Specifically, due to stark socioeconomic inequalities, urban elites are able to overconsume water while excluding less-privileged populations from basic access. Through an interdisciplinary approach, we model the uneven domestic water use across urban spaces and estimate water consumption trends for different social groups. The highly unequal metropolitan area of Cape Town serves as a case in point to illustrate how unsustainable water use by the elite can exacerbate urban water crises at least as much as climate change or population growth.
The sustainable management of urban water supply constitutes one of the key challenges of our time1. During the first two decades of the twenty-first century alone, more than 80 large metropolitan areas have experienced extreme drought and water shortages2. Urban water crises are expected to become more frequent3, with over one billion urban residents projected to experience water shortages in the near future4,5. In both the Northern and the Southern hemispheres, metropolitan areas experience extreme droughts and unsustainable levels of water consumption6 (Fig. 1). In the face of fluctuating supplies, meeting the growing urban water demands and finding a sustainable balance among the city, its rural hinterland and environmental flow requirements is becoming increasingly challenging4,7,8.
Scientific studies tend to explain increasing water demand as a consequence of the expansion of urbanized areas alongside population growth4. Climate change, in most cases, is considered the force that jeopardizes the availability of freshwater resources by altering the spatiotemporal characteristics of temperature and precipitation2,9. Physical and engineering sciences have made important progress in advancing methodologies to capture the intensity of anthropogenic pressure on hydrometeorological hazards and their resulting water crises10. However, these analyses fail to recognize how social power and heterogeneity in society shape both the way urban water crises unfold and who is vulnerable to them. The problem with depoliticized analyses is that they often lead to technocratic solutions that are likely to perpetuate the same logic and, in turn, reproduce the uneven and unsustainable water patterns that have contributed to the water crisis in the first place10.
In this Article, we interpret urban water crises as social-environmental extremes11 and retrace hydroclimatic and sociopolitical processes generating the increasing gap between water supply and demand, along with the resulting uneven levels of water insecurity. In particular, we draw on critical social sciences to explain urban water crises as generated by asymmetrical power relations that determine who controls water and how water is redistributed within a city12,13,14,15. This scholarship explains that conditions of water scarcity and limited access to water result from the prevailing politics and power dynamics that govern the city16,17,18.
Building on this critical understanding of society, we develop a system-dynamic model that represents unequal human–water interplay within a city. We specifically analyse domestic water use of urban residents to capture how economic inequalities shape consumption trends and, in turn, urban water crises. Our model shifts the focus away from averages of urban water consumption and simulates consumption levels across different social groups. This approach allows an exploration of the role that the elite and higher-income classes play in the water balance of a city, while also assessing their ability to respond to drought-related water crises relative to other social groups. Specifically, to account for urban inequalities, the model is discretized into households that are further reaggregated into distinctive social groups. The social power of each such group is expressed through different parameters and coefficients that differentiate water access and consumption patterns across the city. This model employs the metropolitan area of Cape Town as a case in point for two main reasons. First, the city is marked by stark socioeconomic inequalities and a starkly segregated urban space. Second, between 2015 and 2017, Cape Town experienced a severe drought, which unfolded into an unprecedented water crisis, widely known as Day Zero. The model simulates the uneven water consumption across Cape Town’s different social groups before, during and after the occurrence of the drought, thereby exploring and assessing the implications that consumption by elites have on the sustainability of the urban water system. Cape Town’s urban form and features are not unique to this city but rather are common to many metropolitan areas across the world19. Thus, the model is flexible and can be adjusted to analyse urban water dynamics in other cities characterized by socioeconomic inequalities, uneven patterns of water consumption and varied access to private water sources and public water supply. Specifically, the model can reproduce water consumption patterns at the household level and simulate the aggregated impact of each social group on the urban water balance.
We first describe the model’s estimates of different water consumption levels across an unequal urban space. The results highlight the disproportionate water uses of privileged social groups relative to the rest of the city. Next, we examine patterns of water inequalities during the occurrence of drought. These results show that each social group diversely experiences and responds to drought events. Last, we compare five scenarios to assess the influence that privileged water consumption has on urban water balance relative to other potential drivers. The results of this numerical analysis show that water crises such as the Day Zero drought in Cape Town are also a product of the unsustainable practices of the elite brought about by the uneven power dynamics of the city. Thus, rather than being reactive, future drought resilience strategies should be more proactive and be able to recognize the long-term socioenvironmental patterns that engender urban water crises. Hence, this model opens up possibilities for more just and sustainable approaches to managing and distributing water in cities.
Water access and consumption across unequal urban spaces
The system-dynamic model uses Cape Town as a case in point to simulate different consumption patterns across an unequal urban space. In particular, on the basis of the Socio-Economic Index developed by the Western Cape Province (Case study), the urban population can be classified into five social groups: the elite, upper-middle income, lower-middle income, lower income and, ultimately, the informal areas20. According to the 2020 census, 1.4% of the city inhabitants belong to the elite and 12.3% to the upper-middle-income group. While 24.6% are classified as lower-middle-income group, about 40.5% of the population live in lower-income areas and 21% inhabit the shacks of the informal settlements scattered at the edges of the city21. Throughout the paper, the elite and upper-middle-income areas are clustered into the broader category of ‘privileged groups’. These groups usually live in spacious houses with gardens and swimming pools and consume unsustainable levels of water, while informal dwellers do not have taps or toilets inside their premises22. On average, the model estimates that the elite and upper-middle-income households can reach a water consumption of respectively 2,161 litres per household (HH) per day and 988.78 l HH–1 d–1, while lower-income and informal households are estimated to consume about 178 l HH–1 d–1and 41 l HH–1 d–1 (Fig. 2a).
The stark differences in water consumption patterns resulting from this simulation are largely confirmed by literature from Cape Town and other cities, which suggests that income is a major factor influencing domestic water use22,23,24. Overall income level, type and size of house, and amenities are key to explaining the relatively higher level of water consumption among elite and upper-middle classes. In addition, the results show that most of the water consumed by privileged social groups (elite and upper-middle income) is used for non-basic water needs (amenities) such as the irrigation of residential gardens, swimming pools and additional water fixtures, both indoor and outdoor. Conversely, most of the water consumed by other social groups (lower-middle income, lower income and informal dwellers) is used to satisfy basic water needs such as drinking water, hygiene practices and basic livelihood (Fig. 2a). What is most striking from these results is the total amount of water consumed by the elite and upper-middle-income groups. Despite representing only 1.4% and 12.3% of the total population, respectively, elite and upper-middle-income groups together use more than half (51%) of the water consumed by the entire city (Fig. 2b). Informal dwellers and lower-income households constitute together 61.5% of Cape Town’s population but consume a mere 27.3% of the city’s water. Privileged groups have access to private water sources in addition to the public water supply (Fig. 3b). Although we use the term ‘private’ to identify the additional sources used mostly by privileged social groups, these sources become private only after a process of enclosure and dispossession of common water resources (mostly groundwater) for the sole disposal and benefit of privileged users25.
These excessive and uneven consumption patterns are rooted in the modern political–economic system, which fosters consumerism in the name of individual freedom, financial merits and economic growth26,27. While benefiting a privileged minority, this political–economic system is unsustainable because it reduces the availability of natural resources for the less-advantaged population and causes various forms of environmental degradation27,28. Overall, these results support the argument that domestic water consumption in unequal urban areas such as Cape Town is likely to become unsustainable as a result of excessive consumption among privileged social groups. Specifically, privileged water consumption is unsustainable because in the short term, it disproportionally uses the water available for the entire urban population. In the long term, privileged consumption constitutes an environmental threat to the status of local surface- and groundwater sources. By unsustainably using public water, well-to-do Capetonians directly affect the amount of water available in the city’s reservoirs. Concurrently, when employing private boreholes, these privileged groups could eventually deplete the groundwater sources of the area.
Unequal drought experiences and responses
The model simulates how a city unequally experiences droughts and resulting water crises. In agreement with most literature about urban droughts and their social impacts15,29, the model’s results indicate that water management strategies to cope with droughts can seriously affect the water security of poor households by reducing their access to water. Specifically, the model reproduces the various droughts that occurred between 2008 and 2019 across the metropolitan area of Cape Town. Besides the 2011 drought, the most significant event occurred between 2015 and 2017 and engendered one of the most extreme urban water crises ever recorded. Towards the end of that meteorological drought, the dams of the Cape Town Water Supply System had reached the alarming level of 12.3% of usable water. In response, the municipality imposed severe water restrictions and other measures to avoid ‘Day Zero’, the day in which the entire city would have run out of water. The restrictions included water rationing to 350 l HH–1 d–1 (or 50 l person–1 d–1), increased water tariffs, fines for overconsumption or illicit water uses, withdrawal of the free water allocation for households classified as non-indigent and other measures to enforce the compliance of such restrictions22,30. The increasing block tariff, designed to charge incrementally higher rates to heavier consumers and cross-subsidize light users, was only partially successful in meeting the needs of the poorest population. Indeed, low-income users could not afford the revised tariff. Very often, these residents live in overcrowded units where more than eight people share the same tap and end up being charged unaffordable water bills and fines22,23. The model accounts for these water restrictions and reproduces the drought responses of different social groups. Accordingly, the water consumption trends simulated by the model (Fig. 3b,c) indicate that low-income residents are significantly more vulnerable to the demand-management measures enforced by the city than are more-affluent inhabitants, who can afford tariff increases and can access and develop alternative water sources.
In particular, the water consumption trends in Fig. 3b show that throughout the drought period of January 2015 to July 2017, the lower-income group had to reduce their already limited daily consumption from 197 l HH–1 d–1 to 101 l HH–1 d–1, a reduction of 51%. These results indicate that drought-related restrictions can leave lower-income households without enough water to meet their basic water demands for bathing, laundry, cooking and sustaining their livelihoods. Conversely, the consumption trends of the elite and upper-middle-income groups show that these households have sufficient water for their basic needs even during drought restrictions. Privileged groups experienced the highest reduction of water use during drought but also a quick recovery from drought-related shocks. From, respectively, 2,542 l HH–1 d–1 and 1,103 l HH–1 d–1, the per capita water use of the elite and upper-middle-income groups fell to 1,604 l HH–1 d–1 and 699 l HH–1 d–1 (Fig. 3b). Yet although such households recorded the highest reductions of water use relative to lower-income households, their reductions were due largely to the suspension of non-basic water uses such as garden watering, car washing and filling swimming pools.
Privileged groups are shown to access higher amounts of water and are thus more resilient to drought relative to the lower-income groups (Fig. 3c). The higher amount of water available for the elite and upper-middle-income households in the immediate aftermath of the drought is explained largely by the ability of these privileged groups to access alternative water sources. In the short term, additional sources encompassed mostly bottled and spring water. In the longer term, elites’ strategies to cope with reduced public water availability extended to the development of private water sources, such as rainwater harvesting systems or boreholes located on the premises of their households. Figure 3c shows that restrictions on public water use triggers a significant increase in consumption of water from private boreholes for only the social groups that can afford the access and use of such sources. By contrast, low-income areas do not have the resources to cope with tariff increases or to access private water wells. For each simulated drought, Fig. 3c shows that after drought periods, private water use by the elite and upper-middle classes increases, respectively, up to 7.5% and 1.3% relative to public water use. At the same time, informal dwellers and lower-income groups (with, respectively, 0.04% and 0% maximum ratios) do not have access to these private sources.
Ultimately, as depicted by the simulated water consumption trends (Fig. 3b, c), the elite and upper-middle-income groups tend to enhance their level of water security after a drought while low-income groups become more water insecure. Such trends also reveal differentiated levels of resilience to future droughts across different social groups. Privileged households are not affected by tariff increases and continue to rely on the private water sources developed in response to the recent drought. On the contrary, low-income groups become less resilient as they cannot easily afford the tariff increases that have become permanent after the drought, and they have limited or no access to private water sources. This uneven picture is rooted in the water inequalities observed before the drought and, in turn, the socioeconomic features that characterize Cape Town’s urban fabric. From here it follows that the manner in which each social group experiences and responds to drought is also rooted in the distinctive political–economic regimes that shape urban form and conditions of access to water and other resources22,28,29.
Impact of elites’ unsustainable consumption on urban water balance
The simulation of the different water consumption trends shown in Fig. 3 reveals that the unsustainable water consumption by the elite and the upper-middle-income groups constitutes a threat for the long-term sustainability of an urban water system. Moreover, the increasing use of private boreholes by these privileged groups represents an environmental threat for the local aquifers. Specifically, the availability of private boreholes within the premises of elite or upper-middle-income households risks triggering what ecological economists31 and sociohydrologists7 define as the supply–demand cycle. The supply–demand cycle attributes an unforeseen increase in water demand to the expansion or construction of additional water infrastructure. In this case, the development of private boreholes by the most privileged groups could produce a supply–demand cycle, which, in the longer term, might deplete the local aquifers and thus limit the future availability of water for basic needs. These results are relevant for any city that allows privileged groups to consume at comparable levels to those observed among Cape Town’s elites. The risks are even greater considering that drought projections suggest that meteorological and hydrological droughts will most likely increase across South Africa and in many other regions of the world32,33,34.
Finally, to test the extent to which water consumption by the elite and upper-middle-income groups contributes to urban unsustainable water patterns, the model simulates a number of scenarios. Each scenario examines the implications of different drivers on the long-term patterns of urban water consumption. Specifically, the model compares the (1) baseline with scenarios of (2) urban population growth by 2% per year35; (3) climate change with an increase in temperature of 2 °C36 and a 10% decrease in run-off37; (4) increase in unsustainable water consumption by the privileged groups; and (5) more equal and sustainable use of water by every social group. Although these drivers occur simultaneously, we simulate them separately to perform a scenario-based analysis of the relative impacts that each driver might have on the city’s water balance. Figure 4 shows that the most unsustainable scenario is the one that foresees an increase of inequality and, in turn, unsustainable levels of water consumption among the elite and upper-middle-income groups. Here an increase of unsustainable water consumption by the most privileged social groups has the potential to be more detrimental than the effect of population growth (on water consumption) or climate change (on the availability of surface water sources). Concurrently, the results of the population growth scenario do not significantly deviate from the baseline conditions. Instead, the climate change scenario interestingly shows that as a result of extreme drought conditions and related water restrictions, the elite and upper-middle-income groups considerably increase their access and usage of private boreholes, thereby substantially depleting the groundwater resources available within the area. Last, the scenario that considers a more equal distribution of water across the different social groups along with more sustainable levels of consumption leads to reductions in total water use and pressure on the urban water balance. In this scenario, private boreholes are not exploited and the local aquifer remains relatively preserved. Thus, with respect to Cape Town, we conclude that if every social group had used a similar amount of water and limited the amount of water used for amenities, the city could have averted some of the worst effects of Day Zero.
Projections of future water demand and drought show an alarming risk of water crisis for many, if not most, cities across the world38. The management of urban water systems thus represents one of the most compelling and serious challenges society must address. Current policies aimed at tackling drought and urban water crises focus mostly on building resilient cities through additional as well as more-efficient water infrastructure and technologies, alongside progressive water pricing9,39. Yet such techno-managerial solutions are insufficient to address future water crises because they overlook some of the root causes. First, as we have shown here, resilience strategies relying solely on increased water supply are counterproductive as they expand the water footprint of cities while perpetuating unequal levels of consumption. Second, as shown by our results (Fig. 3), even when aimed at cross-subsidizing low-income households, increasing tariffs have proved ineffective in terms of both fairness and environmental sustainability. Thus, future drought resilience strategies should shift away from reactive approaches based on the notion that droughts are episodic. Instead, more proactive adaptation strategies are needed to recognize and address the long-term socioenvironmental patterns that engender urban water crises.
Our results show that urban water crises can be triggered by the unsustainable consumption patterns of privileged social groups. Critical social sciences explain that these patterns are generated by distinctive political–economic systems that seek capital accumulation and perpetual growth to the exclusive benefit of a privileged minority15,18. In other words, there is nothing natural about urban elites overconsuming and overexploiting water resources and the water marginalization of other social groups. Instead, water inequalities and their unsustainable consequences are products of history, politics and power16.
To conclude, theories on degrowth suggest that the only way to counteract the unsustainable and unjust patterns of elites is by reimagining a society in which elitist overconsumption at the expense of other citizens or the environment is not tolerated40. Our analysis confirms that the only way to preserve available water resources is by altering privileged lifestyles, limiting water use for amenities and redistributing income and water resources more equally. The difficulty with such actions is that they stand in stark contrast with the prevailing political–economic system built on overexploitation of natural resources alongside the exclusion, segregation and marginalization of underprivileged classes41. We suggest reorienting current water management and drought adaptation policies towards new political–economic paradigms that prevent overconsumption and inequalities. As Cohen29points out, “the era of cheap and plentiful drinking water has passed”: it is time to agree about how society should share life’s most essential natural resource.