The Next Path for Water

Professor David Sedlak of UC Berkeley and author of Water 4.0 shares his perspective on the next path for water management.

First, came the hard path.  To meet the needs of rapidly growing populations and expanding economies in the years following the Second World War, society went on a water infrastructure spending spree. Between 1950 and 2000, we built about 40,000 large dams, and created dozens of inter-basin transfer projects that dwarfed the aqueducts of the Roman Empire or the qanats of the Ancient Persia.

Beyond the costs of concrete and steel needed to create all this water infrastructure, the world paid a steep price for following what has been referred to as the hard path.  Tens of millions of people were displaced by dams and water projects.  Aquifers were sucked dry and entire lakes disappeared.  Unrestrained development of water infrastructure took a toll on the environment, too, blocking the movement of fish, depriving river deltas of sediments and creating conditions that led to the collapse of sensitive ecosystems.  By the end of the twentieth century, as the world recognized the true costs of water infrastructure, the hard path lost much of its luster.

In response, water managers turned to the soft path.  Over the past 40 years, many of the world’s largest cities have met the needs of expanding populations without building more infrastructure.  This has happened through actions like incentives on the purchase of water-efficient appliances. Utilities and governments have even made some progress in educating consumers about the need to use water more wisely and other forms of demand management.

Four decades ago, when the soft path was first becoming popular, water providers turned to it because there was slack in the system.   In many cases, demand management was the least costly and environmentally damaging ways of meeting the needs of society.  Now that the easy steps have been taken, that may no longer be the case.  In light of the challenges posed by growing demand and shrinking supplies due to population growth and climate change, we may need an all-of-the-above approach.  This means finding ways of using water more efficiently.  But it also means that we need to reuse more water and, in some cases, expand the supply.  Let’s call this the ‘next path’.

The next path is not a return to the hard path, nor is it exclusively a matter of more soft path solutions.  It is a hybrid of the two approaches, informed by the experiences of the past and enabled by technological advances that are transforming other aspects of society.

To illustrate the potential for new technologies to catalyze the next path, we can consider three themes have emerged from reviewing research needs related to desalination and advanced water treatment. Recently, I was fortunate enough to be a part of a research roadmapping effort from the National Alliance for Water Innovation (NAWI)—a newly launched initiative from the US Department of Energy to address water insecurity at the national scale.  (See

The first theme that emerged as being a key area of research is the IT revolution.  When it comes to water quality and quantity, sensors, actuators and data processing algorithms can allow us to get more out of our existing infrastructure and possibly create small-scale, autonomous systems.  We have been hearing about this for over a decade, but it still needs a push to get it where it needs to go.  With a bit more effort directed at bringing the IT revolution to water, we may finally be able to realize new modes of water supply that do not require on-site operators to assure water safety.

Presently, there are many R&D efforts underway to realize the promise of digital twins and autonomous control.  A key challenge is the interoperability of data from multiple sources in a common platform as a means of  making the most out of these new data streams.  Development of digital water also will advance if data streams can be opened to researchers who can use them as living laboratories, creating algorithms necessary for optimizing operations and anticipating and responding to process upsets.

The second theme that we observed as being important is related to the need to unlock the full potential of desalination technologies. As was the case with solar and wind power, with every passing year, the cost of desalinating water drops relative to the established approaches.  For example, the cost of installed capacity for seawater desalination dropped by a factor of three between 1970 and 2000 as the technology matured. As evidenced by experiences in Israel, Australia and most recently, Southern California, it has matured to a point at which it is less expensive than new sources in many water-stressed cities.

The last theme that we identified is related to using IT and advances in modular water treatment technologies to safely operate networks of small-scale treatment facilities. This offers the possibility of tailoring treatment to the needs of the user and creating more flexible systems that do not require a centralized treatment plant and an expensive underground pipe network.  The idea of non-grid solutions and hybrids of centralized and decentralized treatment has been gaining traction in response to the challenge of sanitation and resource recovery from sewage.  In addition, electrification of the remainder of the treatment process can play a key role in enabling distributed treatment systems.

Over the past two decades, we have developed a vocabulary for articulating our aspirations for the future of water management.  One water.  The circular economy of water.  Integrated water resources management.  These terms all recognize the need to expand the palette of solutions to access non-traditional sources and to think in a more systematic way about the effects of our water use on others and the environment.

This next path requires that we expand our perspective, bringing along the lessons of the hard and soft paths.  We also will have to bring in new technologies in a manner that integrates with existing water systems and institutions, while simultaneously adapting to a changing climate and different expectations about the services that water systems provide.  I can think of no group of people who are better poised to take on this challenge than the water professionals who are part of IWA.


This blog is an extract from Professor David Sedlak’s speech given during IWA’s Digital World Water Congress 2021. To watch the entire keynote, please click here, and watch from 16:47. 

David Sedlak

Professor, UC Berkeley