Oil shaped the industrial city; water availability may shape the next generation of cities. From the earliest human settlements of the Indus Valley to the densely populated cities we live in today, access to water has always been a key driver of the growth and expansion of societies. Water enabled habitation, trade, and the sustenance of ecosystems around which early settlements developed. Water was not merely a resource within a settlement, but a key condition that made the settlement possible. Thousands of years later, another resource transformed the scale and character of urban development: oil, a defining force of the modern world. Since the Industrial Revolution, the world has expanded on the shoulders of this resource. It powered industries, transport and construction; enabled global trade; pushed societies to expand beyond their boundaries; and connected the world. But as the world has grown and evolved, we have realised that cities cannot run on energy alone. They need to be sustained by natural resources, and there needs to be a strong approach to ensuring the sustainability and security of these resources. Among these resources, water remains perhaps the most fundamental, woven quietly into every layer of urban life. Turn on a tap, and the story seems to begin there. But in reality, it began much earlier—with rainfall, a river, a reservoir or an aquifer. When the tap turns off, the story doesn’t end. Water keeps moving, even when we cannot see it. Water We Don't See Modern cities have become very good at making water disappear. Rain falls on a roof and is directed into a pipe. It reaches the street and enters a drain. Wastewater leaves a building through another network of pipes and disappears underground. Somewhere outside the visible city, treatment plants receive it, treat it, and release or reuse it. This system has obvious advantages. It allows people to live without having to think about where their water comes from or where their waste goes. But perhaps this convenience has created a very strange disconnect: the more successful water infrastructure becomes at hiding water, the less aware people become of the systems that sustain it. We have become so accustomed to water being available at the turn of a tap that we rarely think about the systems that make that possible. The city begins to look alienated from the water cycle. A river becomes something that flows outside the city. Rain becomes something to drain away. Groundwater becomes something beneath the ground that can be pumped when required. Wastewater becomes something that leaves the building and is no longer our concern. But none of these systems actually stop at the city boundary. The water we withdraw from an aquifer affects what remains. The wastewater we discharge affects the river downstream. The concrete we lay over soil affects how much rain can infiltrate. The city is not outside the water cycle. It is part of it. This also changes the way we think about drinking water and sanitation. Water security is often reduced to a simple question: Do people have access to enough safe drinking water? It is, of course, a fundamental question. But it is only the beginning of the story. We drink it. We cook with it. We bathe in it. We flush it away. And yet, our understanding of water often ends at the tap. Water enters our lives → we use it → sanitation takes over → wastewater begins its second life. What happens after the water has been used? Sanitation is not simply about getting rid of waste. It is about determining what happens to water after we have used it, and whether we allow that water to become a source of pollution or an opportunity for recovery. This is where the idea of a circular water economy becomes relevant. The traditional urban model is largely linear: Water enters the city → it is used → wastewater is discharged. A circular approach asks whether we can instead create more loops. The difference may look small on paper, but it represents a significant change in how we understand water. A treated wastewater stream could support landscape irrigation or toilet flushing instead of immediately becoming an effluent stream. Rainwater could be stored or allowed to infiltrate rather than being treated only as runoff. Organic matter in wastewater can contribute to energy generation or nutrient recovery. The idea is not to reuse every drop endlessly. Some water must return to rivers and aquifers to sustain the ecosystems that support us. Circularity is not about eliminating the natural water cycle with an engineered cycle. It is about working with the natural cycle rather than constantly interrupting it. Designing with Water This is where the conversation moves beyond pipes and treatment plants and into the city itself. For a long time, cities have been planned largely to control water: keep rain out of buildings, move wastewater away, and make surfaces dry quickly. This made sense when the primary objective of planning was sanitation and flood prevention. But cities today are dealing with a different set of problems: water scarcity in certain regions, falling water tables, intense and delayed rainfall, polluted water bodies, and increasing pressure on existing infrastructure. There is something particularly strange about the way cities experience water today. Some cities are running out of groundwater while struggling with water supply. The same cities can experience severe flooding when intense rainfall arrives. Lakes disappear while streets flood. Rainwater is scarce in a dry season and a nuisance during a cloudburst. This is not a contradiction in nature. It is often a contradiction in the way we have designed the water supply system of the city. When large areas of land are covered with concrete and asphalt, rain has far fewer opportunities to enter the soil. Water moves away quickly instead of being stored or infiltrated. At the same time, growing populations continue to draw from groundwater and distant water sources. So, perhaps the real challenge is not simply that there is too little water, but that when a city receives water, it arrives at the wrong time, in the wrong place, or in poor quality—or the city isn’t capable of capturing it so that it can benefit from it. That makes water management as much a question of time, space, and design as it is of quantity. Perhaps the perception needs to evolve from keeping water away from the city to integrating water within the city. A roof can be more than a surface that sheds rain. It can become a source of stored water. A street can be more than a channel for traffic. Its landscape can allow rain to infiltrate. A park can be more than recreational space. It can temporarily hold stormwater during an extreme rainfall event. A wetland can be more than an ecological feature. It can become part of a city’s water-treatment and flood-management system. This is where innovations and ideas such as Water Sensitive Urban Design, Sponge Cities, blue-green infrastructure and nature-based solutions begin to make sense. They are different approaches, but they share a common principle: water is no longer seen merely as a service to be supplied and managed, but as a system that should shape the city itself. It becomes part of the spatial logic of the city. A circular water economy, then, is not simply a new way of treating wastewater. It asks us to look at the city as a connected water system. Where does the rain go? Where does drinking water come from? Where does wastewater go after it leaves a building? How much water can be safely reused? Where can groundwater recharge? Which landscapes should be allowed to hold water? And perhaps most importantly: what if these questions were considered while designing the city, rather than after the city had already been built? The water-sensitive city may therefore look different from the conventional city—not necessarily because it has more water infrastructure, but because that infrastructure becomes more integrated with buildings, streets, landscapes and natural systems. The industrial city was designed around the extraction and consumption of resources; the water-sensitive city may need to be designed around circulation, reuse and regeneration. The future city may not need to hide its relationship with water. It may need to make that relationship visible. Oil shaped the industrial age by determining how cities moved, produced and expanded. Water may shape the next urban age—not because it will replace oil, but because its availability will increasingly determine where and how cities can grow. “Perhaps it will become the resource that teaches us to think and build differently.” This article is written by Sneha Sharma, Rajat N. Joshi, Anshul Yadav , Department of Water Resources Development & Management, Indian Institute of Technology Roorkee, Uttarakhand [Published in NIWAS Vartika - Vol-II, Issue-2 (Jul-Sept'26): A WASH magazine by SPM NIWAS, MoJS, GoI]