Water is both singular and essential. Yet, for much of recent history it has not been managed as one resource. Instead, it is addressed by a range of fragmented disciplines, cultures and institutions, each aimed at solving distinct challenges for human society.

Different sets of engineers have helped us figure out how to irrigate crops, how to prevent floods, how to deliver clean drinking water, how not to befoul our cities with sewage, and how to sustain healthy rivers. 

This specialization has served its purpose. We are steadily chipping away at water’s fundamental challenges, to the point where we can now envision a world where everyone has access to clean water and sanitation.

While we are not there yet, this ambition is only possible because water professionals, armed with focused expertise, have solved basic challenges for billions of people. 

But the virtues of one era can easily become the sins of the next. Our climate is changing, and with it, the world of water must become more adaptive and resilient. That means embracing a new paradigm of One Water.  

The One Water Paradigm Shift

We have invested much of the last 150 years building infrastructure and institutions designed to ensure reliable access for growing urban populations in a generally stable climate. An environment of relative plenty has enabled the luxury of waste, affording us the collective delusion that there is such a thing as wastewater that is too horrifying to drink. 

The success of our engineers has rendered water infrastructure invisible, so commonplace and reliable that it is seen as a purely technical affair: generally unremarkable, and certainly not a matter for debate.

But in the past 150 years, the world has added 6 billion people and increased atmospheric CO2 concentrations by nearly 50%, at a pace that if left unchecked, will lead to a dangerously warmer world by 2100. Water is the vector through which climate change will cause the most suffering: the United Nations projects that 5 billion people could face water shortages by 2050, with 1.2 billion facing displacement from climate-related natural disasters. 

Faced with such a sobering outlook, we have no choice but to ask different questions of our specialists: how to purify the water we have used so that it can wash our children, how to incentivize agriculture to get more crop per drop, and how to turn cities into sponges that absorb floods and release them during dry spells. Moreover, when infrastructure changes, water inevitably becomes political: who will benefit, who will pay? Who will go thirsty? 

These questions are why the One Water movement matters. As framed by the US Water Alliance, One Water proposes that we think about water differently – as holistically as the resource presents itself in nature, and with a mindset that it must generate multiple benefits for all stakeholders with watershed-scale thinking and action. 

It means dissolving distinctions between different colors of water, and moving concepts like water reuse and nutrient recovery from the periphery to the center of our profession. Beyond technology, it means creating a systems mindset built around partnerships and inclusion across the cycle of water. Put simply, One Water is the approach that is best suited for the adaptive moment in which we live, and it will require us to work together in new ways.

Disciplinary Foundations of The One Water Approach

Living in a One Water world will also require a technological shift to support the holistic collaboration required for an unpredictably changing world. If the essential tools of traditional civil engineering were the mathematics of fluids in motion, we must now integrate new disciplines into our One Water toolkit, such as hydroinformatics, data science, and public affairs.

Discussions about water uncertainty can dissolve into unproductive squabbles without shared boundary conditions that create common reference points. New tools such as digital twins – models enhanced with data to enable visualization and simulation of alternative futures – can help. These tools create an objective fact base, enable scenario planning, and support adaptive decision-making.

For example, faced with climate variability that stressed the performance of existing infrastructure, the city of South Bend, Indiana built an operational digital twin that optimized its existing infrastructure network with artificial intelligence, creating a smart system capable of predictably reacting to sudden wet weather events. 

To date, the smart sewer system has delivered an 80% reduction in combined sewer overflows and is now in a position to solve its resilience challenges with $500 million less than originally estimated. Just as important to the One Water framework, the city’s digital twin enabled scenario analysis to determine investment pathways that would be most acceptable to the community through fact-based public consultations. 

Charting a One Water Future

As we confront unprecedented threats, the next century of water management will require us to align our engineering approaches and institutions for water management toward a One Water framework. 

This transition is fundamental to delivering on our vision of water systems that support strong economies, vibrant communities and healthier environments – in partnership with the stakeholders who depend on our work. 

Meanwhile, we must accelerate deployment of digital water technologies – sensing, analytics and decision-support tools – across water management systems, to meet the challenges confronting our sector affordably while breaking down the barriers that stand between us and a future of managing our most essential resource, together.