Cape Town, South Africa faced a crippling drought between 2016 and 2018. The widely reported "Day Zero" crisis, wherein the city faced the real possibility of the taps being turned off, presented an acute shock and highlighted major vulnerabilities in the city's water supply system, which relies largely on six large dams. Due to a combination of demand incentives, intensive supply management, and behavioral change campaigns, Cape Town was able to avert "Day Zero". However, the crisis provided a number of useful lessons and exposed the critical need for a water system rooted in principles of resilience and a renewed technical approach to water management aimed at equity, sustainability, and water sensitivity.

Having recently acknowledged World Water Day 2022, it is an opportune time to reflect on how the crisis in Cape Town was yet another expression of the growing water turbulence characterizing our world today. Water scarcity is becoming an increasing threat because of climate change impacts (including changing rainfall patterns and rising temperatures) and increasing water demand. Symptoms such as dysfunctional sanitation in urban slums, deteriorating water quality in river catchments and aquifers, and extensive biodiversity loss are critical warning signals that conventional urban water management is ill-suited to address water security concerns.

Water scarcity is becoming an increasing threat because of climate change impacts and increasing water demand.

In urban areas, human-centered processes govern the water cycle; urban water users do not consume water but rather pollute it. Water security is thus more than a quantity issue; it considers quality, productivity, attitudes and behaviors, and governance. Effectively managing water scarcity requires multidisciplinary perspectives in complex decisionmaking structures—engineering, planning, hydrology, environmental and climate science, social science, policy expertise, and more.

A multidisciplinary academic team from three higher education institutions in the Western Cape province of South Africa came together following the Cape Town drought to explore different responses to water scarcity across the world—in a collaboration named "Cities facing escalating water shortages". Six task teams were established to consider political, economic, technical science, natural science, social science, and civil society aspects through several workshops with 50 diverse stakeholders. The collaboration produced an edited collection of position documents that address these multiple perspectives on urban water security in a publication titled "Towards the blue-green city: Building urban water resilience".

The five key lessons that had already emerged from the Cape Town water crisis were sharpened during the "Cities facing escalating water shortages" collaboration as follows:

Create water-sensitive and resilient cities that include the concepts of the "city as a catchment", water quality management, livability, ecosystem protection, and climate change adaptation.

Practice integrated water planning and management that ensure sustainable and equitable water access.

Build water-smart cities that are connected with real-time relevant data and information that is shared widely.

Ensure a collaborative and supportive governance environment to unlock synergies.

Cultivate informed and engaged water citizens, and empower residents, government, businesses, NGOs, and the agricultural sector to make a difference.

These principles emphasize the necessity to consider the urban water cycle as an integrated system that is intrinsically connected to the wider catchment and its varied users, as well as the urgent need to incorporate climate adaptation measures as part of water management in cities. In order to realize the vision of a water-sensitive city, innovative infrastructure design and governance options need to be adopted—including building a diversity of supplies that provide water that is fit for purpose and that is underpinned by timely and actionable water data, not only for management purposes but to create "water-savvy" citizens. A renewed technical approach also speaks to the importance of multifunctional, blue-green infrastructure and enhanced ecosystems. Critical to this is an enabling governance, political, and legislative environment led by multidisciplinary teams that facilitate and entrench equity, resilience, and sustainability in day-to-day practices.

These key lessons that emerged from the water crisis extend to all urban areas in water stressed regions of Africa that are struggling to grapple with increasingly water-turbulent times. The grand scale and "wicked" nature of current urban water challenges driven by climate and population changes, resource pressures, and water pollution sound out the call for a renewed technical agenda and water-sensitive approaches within cities.