DAVID SEDLAK: Water for All: Global solutions for a changing climate

Dr. David Sedlak is a Professor of Civil and Environmental Engineering at the University of California, Berkeley, and director of the Berkeley Water Center and chair of the National Academies of Sciences, Engineering, and Medicine’s Water Science and Technology board.  Dr. Sedlak is the author of Water 4.0: The Past, Present, and Future of the World’s Most Vital Resource.   In this Arizona Water Resources Research Center webinar, Dr. Sedlak discusses his latest book, Water for All: Global Solutions for a Changing Climate.

Dr. Sedlak began by noting that he didn’t set out to become an author, but through his work on potable water recycling in the mid-2000s, he recognized the public’s interest in learning more about water systems.  This led him to write the book, Water 4.0

“One of the things that I learned in writing Water 4.0 was that water systems are very resistant to change, and when stress comes on, they try to adapt themselves incrementally.  But every now and then, a stress comes that is just too big for the system to handle, and a revolution takes place.

“The premise of Water 4.0 was that there were three prior revolutions in urban water systems.  And what we’re seeing in places like the American Southwest, Singapore, and other places around the world was a fourth revolution.  And if we could understand it better, we would be able to bring it about.  Writing that book was a great experience because it exposed me to a much broader world.  These people not only dealt with urban water issues but issues related to water and agriculture, water in countries with varying income distributions, and a whole host of things.

But I quickly recognized that I had written a book about water for wealthy people living in cities, and water was so much more.

So, over the past ten years, I’ve challenged myself to learn about that broader aspect of water.  What I hope to do today is to share with you some of the things that are in the latest book, Water for All, and to put the types of challenges that you’re experiencing in Arizona and the American Southwest into a larger context, so you could understand that the issues being dealt with on the Colorado River and other places are similar to what’s going on in much of the rest of the world, to understand the drivers and solutions that might be relevant to your situation, and the way in which innovations being developed in Arizona might find applications elsewhere in the world.”

THE GREAT ACCELERATION

The book, Water for All, is about the global challenges associated with the changing climate, but first, it’s important to understand one of the key drivers of change in the water sector: the ‘Great Acceleration” or the Anthropocene.  The slide shows 12 figures from a pioneering paper by Stefan et al., which provides a snapshot of how the world has changed since the second half of the 20th century.

In the second half of the 20th century, there was a period of tremendous population growth, significant technological innovation, and a great increase in wealth worldwide, which had important implications for water systems.

Dr. Sedlak gave an example: “In the 19th century, one of the largest cities in the world was London.  The population of London was doubling about once every 40 years, which meant that the water managers in London had to expand the infrastructure to serve the community at a rate of a few percent a year.  In the second half of the 20th century, the city of Los Angeles was doubling about once every 30 years, so in terms of the pace of construction and new projects and the like, it was similar in scale to London.”

He noted that the graphs differentiate between the OECD countries (the wealthy countries), the BRICS (Brazil, Russia, India, China, and South Africa), and the rest of the world, including Sub-Saharan Africa and parts of Asia that are rapidly growing.

“What you can see is that population growth is slowing down in the OECD countries; it’s even starting to slow down in the BRICs, but it’s still accelerating in other countries.  So this is an issue that is particularly relevant when we think about water challenges being faced in the global south.”

“The second driver of water challenges is climate change.  And I would say that, up until the last five or ten years, the big driver of water crises around the world was probably the great acceleration of human development, but increasingly, we’re seeing climate change being one of the bigger drivers of water challenges.  So, as we deal with the impacts of wildfires, floods, and flash droughts, we recognize that a changing climate is really stressing and testing the ability of our water infrastructure to provide us with enough water to grow food and water for our cities and industries.”

“For me, one of the big epiphanies of looking a little deeper into climate change and its impacts on water resources was to consider the impact of climate change on the global air circulation patterns, particularly the width of the Hadley cell.  Hadley cells are these global air circulation patterns that start near the equator as moist air rises into the troposphere.  Then they terminate as the now depleted of moisture air comes back down to Earth at about 30 degrees north and 30 degrees south latitude.”

“At these latitudes, 30 degrees north and 30 degrees south, we have the world’s great deserts – the Sahara, the Kalahari, the Mojave, the Sonoran Desert, and the deserts of Australia.  And with climate change, the width of the Hadley cells is expected to increase.  And as the width of the Hadley cells increases, we’ll see less precipitation in the areas immediately north and immediately south of the Hadley cells.  This means we’ll see a decrease in precipitation in the American Southwest and southern Europe.  It’s predicted by the year 2050, these regions will see a decrease in precipitation of between 10 and 20%.”

“Now, that kind of decrease in precipitation has already happened in parts of Australia, where the global ocean circulation patterns have already changed.  For example, in Perth, Australia, the average annual precipitation is about 15%, less than it was in the time prior to the 1950s.  But that 15% decrease in precipitation has translated to about a 50% decrease in the amount of water flowing into the city’s reservoirs.  And that’s because the other big impact of climate change is the ability of the atmosphere to hold more moisture at warmer temperatures.  So, this process – aridification – which is affecting the American Southwest, means that Perth has seen a 50% decrease in their water resources, and they’re not expecting them to return.  So that’s part of why Perth is one of the cities aggressively adopting seawater desalination and potable water recycling.”

THE SIX WATER CRISES

The central idea of the book is that the world is not struggling with a global water crisis; it’s struggling with six separate but interlinked water crises.  Understanding the water challenges in this multi-dimensional way gives insight into the way institutions work to address them.

The six crises:

• Water for the wealthy: People in rich countries have the means to deal with water scarcity with technological solutions such as seawater desalination and water recycling.
• Water for the many: There are billions of people on Earth who live in cities and have access to piped water now that may or may not come into their house, but it likely doesn’t run 24 hours a day.  So people deal with water of fluctuating quality and availability.
• Water for the poor or unconnected: There are close to 1 billion people on Earth who don’t have access to an improved water supply; they might have to walk great distances to carry water back to their homes, or they may have to rely upon trucked or bottled water which costs a significant fraction of their income.
• Water for health: Whether wealthy or poor, your water might be contaminated in some way, such as arsenic, PFAS, or lead.   So, just because people have access to water doesn’t mean they can drink it without additional treatment.
• Water for food: Most humans use water to grow food.  About half of the world’s food is grown in irrigated agriculture.  So, climate and population stress on agriculture make some real challenges.  Certainly, Water for Food is where we see crises developing more in the future.
• Water for ecosystems: There are a lot of impacts on the environment that come from human use of water and the pollutants that we introduce into water.

The book, Water for All, addresses all of these and explains how institutions have developed to address these problems.  It talks about the policy changes that can be made to address these problems, the incremental approach we often use, and some emerging technologies that we might use to find new ways to revolutionize these water systems.

He then discussed two of them: water for the wealthy and water for food.

WATER FOR THE WEALTHY

One way wealthy countries and cities deal with water scarcity is through water reuse.  There are approaches to water reuse in practice across the globe, and one of the themes of the book is that the answer to our water problems can sometimes be found in other places that have been addressing similar kinds of issues for a longer period.

Full advanced treatment has been pioneered by the Orange County Water District, where they take treated wastewater, use reverse osmosis, ultraviolet light, and hydrogen peroxide to disinfect the water and put it into the drinking water supply.  This approach has been adopted in other places, such as Singapore and Perth, and Los Angeles and San Diego are working towards recycling their wastewater in this way.

But it’s not the only way.

In the 19th and 20th centuries, the Dutch pioneered a method of managed aquifer recharge on the dunes down by the coast because the Rhine River was contaminated by sewage and agricultural runoff and runoff.  The Dutch found that by percolating Rhine River water through the sand dunes and pumping the water out of the ground when it became groundwater, they could purify it and make it safe to drink.  This built upon the approach the Germans had used for riverbank filtration along the Rhine for many years before that.

Another approach came from a community in Northern Virginia that treated water with everything they could short of reverse osmosis, such as granular activated carbon, biological activated carbon, chlorination, or ozonation.  It has proven to be a safe and effective way to recycle wastewater.

On the horizon is the idea of water recycling at the individual building scale, sometimes referred to as ‘net zero water.’   It’s part of an idea that captivates architects and the Department of Energy to construct buildings that can be entirely off the grid.

One project that’s built interest in the idea of water recycling at the building scale is the Battery Park City Project, which started in the early 2000s.  It is a cluster of buildings that use a small modular biological treatment system that uses microbes to break down the organics in the sewage and then a membrane for filtering out microbes and particles to recycle about half of the development’s wastewater.  About 10,000 people live there, and about 35,000 people visit the shops and schools there.

“About half of the water footprint has been reduced by in-building water recycling,” said Dr. Sedlak.  “The fact that they proved that this was possible, and perhaps more importantly, the fact that they showed a return on investment for the infrastructure and treatment systems they built within ten years, has motivated others to get interested in the topic of in-building water recycling.”

The city of San Francisco passed an ordinance about a decade ago requiring new buildings above a certain size to install in-building water systems, such as a rainwater tank, membrane bioreactor, or greywater recycling system within the building.  Currently, there are 45 permitted projects and about 30 more projects underway.

“It’s starting to convince water managers and building designers around the world that it may be possible to start recycling water at the building scale and reduce the water demand of the city,” said Dr. Sedlak.

He noted the larger question about whether this makes sense.  “From an economic perspective, some of my group’s research has shown that it can make economic sense. … One of the things we learned is that it would increase the cost of the building by somewhere from 6 to 12% to make the building completely off the grid and that the cost of doing this would be somewhere between $1.50-$2.70 per cubic meter; that’s still about twice as expensive as seawater desalination plants. … For the backup security of being connected to a water and sewer system, the return on investment for this system would be less than ten years.  So it’s possible to build a water recycling system at the building scale with existing technologies, with existing equipment, at the building scale, that could return on investment within ten years.”

In-building water recycling is something we’ll likely see more of in the future, but perhaps the larger impacts are outside of wealthy cities.

In 2020, they did an economic analysis of in-building water recycling at the scale of an individual home and found it could be attractive for rural communities or houses on the edge of cities that don’t have a secure water supply.

Allensworth is a historically black town that has lost its water supply as its neighbors have pumped out groundwater for agricultural use.  They’ve reached a point where their local wells can’t provide enough water, and they’re relying on trucked water, the treatment of arsenic-contaminated water, and even atmospheric water harvesters.  So, buildings off the water grid would be a tremendous asset to these communities.

He also noted that developing cities around the globe, instead of building centralized water infrastructure, could opt for building-scale water systems.  In Bangalore, India, an ordinance now requires new buildings to have their own water systems.

WATER FOR FOOD

Much of the crops grown in the American West are grown with irrigation.  In fact, irrigation was one of the two factors that contributed to the first Green Revolution.

During the great acceleration, we had to feed many people in a very short time, so the innovations included increasing yields with plant breeding, agronomic technology, synthetic fertilizers and pesticides, and irrigation.

But in the latter part of that great acceleration, we also started to run out of water.  In the American West, between 1984 and 2013, there was a transition from gravity or flood irrigation to pressure irrigation using sprinklers and drip irrigation, greatly increasing the amount of food we grow.

The graph on the right shows irrigation use in different countries; the pie charts are shaded according to how irrigation water is applied (surface, sprinkler, or localized, meaning drip irrigation) and are scaled relative to the amount of irrigation water used.

Dr. Sedlak pointed out that the United States, Spain, and Italy have already transitioned from surface or gravity irrigation to sprinklers and drip irrigation.   “The only reason that the United States is not closer to 100% is that we still have plenty of places on the East Coast where water stress is not that high where surface irrigation is used.  But if you look at some of the large irrigators in rapidly growing parts of the world, like China, India, and Iran, you’ll see that there’s still a great dependence on surface irrigation.  So we can see that in the future, a lot more investment is being made in making irrigated agriculture more efficient.”

But with that comes the need to learn from the errors of the past.  Dr. Sedlak pointed out the blue line on the graph on the right, which is total water use, and noted that in the Western US, when greater water efficiency was realized by switching from surface irrigation to sprinklers and drip irrigation, the total water use stayed approximately constant.

This is common when efficiency is introduced to systems when technological innovations happen.  It’s called “Jevon’s Paradox,” which is defined as occurring when technological progress increases the efficiency with which a resource is used (reducing the amount necessary for any one use), but the falling cost of use induces increases in demand enough that resource use is increased, rather than reduced.

“What it leads us to think is that when we implement new types of water policies, or conservation measures, or efficiency technologies, we need to think about how the water that is saved is used,” said Dr. Sedlak.  “We can’t necessarily assume that the person who realizes the efficiency, in this case the farmer, should be entitled to use that water on their farm, especially if government subsidies made the transition possible.  It may be more appropriate to take some of that water and dedicate it to the environment or other water users.  This was certainly the case in the Murray Darling Basin in Australia, where the millennial drought of the early 2000s was an excuse to rethink water rights and uses.”

Treatment technologies are becoming cheaper and more reliable over time, which may lead to applications in agricultural communities.  Innovations are occurring in the municipal sector, such as Eastern Municipal Water District’s use of brackish desalination to clean up groundwater that was too salty to drink at a cost of about $1000 acre-foot.  He pointed out that was possible only because EMWD has access to the Inland Empire Brine Line for brine disposal.   (The Inland Empire Brine Line is a gravity pipeline that delivers brines and other non-reclaimable waste from the Santa Ana River watershed to a treatment plant in Orange County, where it is treated and ultimately discharged to the ocean.)

“In Arizona, Nevada, New Mexico, and eastern parts of California, there are large reserves of brackish groundwater under the surface, but it’s too salty to drink and too salty to use for agriculture,” he said.  “But as desalination becomes less expensive, it may become attractive if we can solve the puzzle of dealing with the brines.”

One method for dealing with brines is called “zero-liquid” discharge, which entails sending the brine to a concentrator, crystallizer, or evaporation pond.  However, these are expensive technologies.

The slide shows an analysis by Department of Energy researchers and the National Alliance for Water Innovation for the project at Easter Municipal Water District.

“The last three bars on the right-hand side show what it would have cost if that Eastern Municipal Water District system had used existing zero liquid discharge approaches,” said Dr. Sedlak.  “What you see is that the cost of post-treatment greatly increases, and the price of desalination approximately doubles.  So we see an opportunity to reduce the cost of brackish water desalination and brine disposal through research and development.”

Dr. Sedlak explained how solar photovoltaic panels on roofs have matured since President Jimmy Carter had photovoltaics installed on the roof of the White House.   As more capacity is built, manufacturing becomes more efficient, innovation and competition happen, and the price drops.  In President Jimmy Carter’s time, solar panels were about 500 times more expensive than what people put on their roofs today.   Similarly, the cost of seawater desalination has dropped by over an order of magnitude in the past 30 years.

Another way technology boosts water for food is through the agricultural reuse of wastewater.  The book gives the example of the Salinas Valley water recycling system, where wastewater from the cities of Salinas, Pacific Grove, Monterey, Seaside, and Marina are collected in a centralized wastewater treatment plant and then used to irrigate crops such as strawberries and lettuces.

“One of the things that I find quite intriguing is that these communities are now contemplating constructing a seawater desalination plant to augment their municipal water supply.  And if they do that, that desalinated seawater will become part of the wastewater and have a second life through the irrigation system.”

RUNNING THE RIVERS

This chapter of the book focuses on the idea that when we address significant problems at the watershed scale, we should recognize that humans are the ones who are responsible for the flow in the rivers and the management of lands surrounding water catchment.

“So this idea of running the rivers is that just about every surface water body in the world these days is controlled by a dam and reservoir, and much of the land that serves as the catchment is also managed by people,” said Dr. Sedlak.

He noted that in the Southwest, hundreds of millions of dollars were used to remove non-native salt cedar trees with the idea that these invasive plants were sucking up water and we were losing it through evapotranspiration.  The thought was that if we could get rid of the salt cedar, more water would flow into our reservoirs.  That was not necessarily correct because other species would take over those ecological niches.

“But that same idea in another context is proving to be one of the most cost-effective ways of increasing water yields,” said Dr. Sedlak.  “In the book, I give the example of Cape Town, South Africa, where the removal of non-native trees in the catchment where the city’s water reservoirs have been located has turned out to be the least expensive way to generate the largest amount of possible water.  So, the city has partnered with a community group with all-female crews that use chainsaws and heavy equipment to remove non-native trees from the catchment.  The proposal was that this would be much more cost-effective and useful than technologies such as water reuse, desalination, or even many of the conservation measures still available to the city, but this wasn’t necessarily obvious.

“So the point I want to make in terms of running the rivers is that we often lack the scientific knowledge to really make informed decisions about how we run these systems,” he said.

THE LAST CHAPTER: THE RIGHT THINGS TO DO

The last chapter focuses on the concept that there is a moral and ethical obligation to think beyond just ourselves with respect to water, particularly the challenges the world faces with the human right to water.

The human right to water is an idea that is taking hold, both here in California and elsewhere in the world.  “In 2012, California passed the human right to water and made it part of our Constitution.  And in 2019, we allocated $1.4 billion to deliver on it.  But realizing that every person deserves a safe, affordable, accessible source of water is proving to be one of the great challenges, so building up more support for a human right to water is very important.”

“Finally, this idea that we have a moral and ethical obligation to ensure water for the environment is also a topic that I explore in some detail, not just through the movement of Indigenous people around the world to obtain rights for river systems and watersheds, but also the idea that there is something that goes beyond even the public trust doctrine to ensure that we protect our ecosystems.”

FINAL TAKEAWAYS

Dr. Sedlak then gave his takeaways:

• The six global water crises will likely be more prominent in the coming decades.
• No single solution will solve the world’s water crises.
• Experience gained in local water crises can be adapted to new locations.
• The costs of technological solutions are likely to decrease.
• Shared stewardship of water is the only viable path to Water for All.

QUESTIONS & ANSWERS

QUESTION:  Regarding in-building water, what are the requirements for backup systems from the utilities?  It’s not different from other kinds of utilities where you have to have the supply to serve if needed, but it may not ever be needed.  How do utilities feel about providing them?

DR. SEDLAK: The best model for how it might play out is the way rooftop solar played out with electric utilities. You put solar panels on your roof but rely upon the electric utility to provide you power at night and in winter.  In the early days, it made sense for the utility to let you do that because there is high demand during the day, and it helped them avoid the construction of new electric power generation.  It’s not a big deal when only one or 2% of the people are doing it.  But when it gets up to 10 and 20%, then everyone else has to make up the difference.  It’s sometimes called the free rider effect; other people will pay more as a result, so you set a connection fee to recognize the cost of the reliability that the utility is providing the backstop.

That needs to be discussed within the utility sector because the real benefit of in-building water systems for water utilities is that they’re pushing the cost of new infrastructure development onto the real estate developer, not the ratepayer.  So rather than build a new reservoir, someone can say,’ I can produce water here; I won’t use as much of your water to bring people into the city.’ And so the utility could consider that a win.

Once it starts cutting into the revenue … the waste from these buildings will be more concentrated; it will have more salt and solids.  And the time that these systems demand water will be in the middle of droughts.  So that is something that is down the road.  In this early stage with San Francisco, it’s such a small fraction of a percent of the city’s water use that it’s not yet an issue.

QUESTION:  Regarding the graphs on Slide 3, what was the data source for that?  Was it based on the global spectrum?

DR. SEDLAK: It is global. The authors of the study were Steffen et al.  There are many appendices with the study, and they provide the data … they had to make assumptions and model a little bit, but the real scholarly contribution was pulling it together.  There are other graphs that you’ll see in that paper.  It is a masterful effort to pull together data and then disaggregate them by region of the world.  It’s a wonderful paper that opened my eyes to the great acceleration.

QUESTION:  Are there policy recommendations to ensure agricultural products are priced to reflect their actual costs and water impact?  Such as, beef costs more than it does today since its water requirements are so high.

DR. SEDLAK: One of the things that I talked about in some detail in the book is how agricultural policy is not necessarily simple, transparent, or logical. That’s because we value the communities that produce our food.  And they often have a lot of political power.  So, something that might make obvious economic sense at the macroscale won’t necessarily happen at the small scale.

One thing we should be thinking about is that farmers generally are economically rational actors, and they’re trying to maximize the amount of food they grow on the water available to them, the land they have, and the markets available.  Government policy can affect what they grow, but governments don’t tell farmers what to plant.  So it’s very complicated, and there are no simple solutions.  We can be frustrated by agricultural policies and pricing, but the likelihood that we’ll be able to change some of these long-held rights and controversies – I’ll just put it this way: I’m not holding my breath for it because I’ve seen 40 years of people pointing out the obvious and the change not coming.  So it comes slowly.  It comes through sustained engagement.  If we can find ways to cushion farmers from the impacts of water scarcity and help them make transitions, then the right decisions are likely to be made.

QUESTION:  What about treated wastewater effluent for agricultural use?  What crops can be grown using treated wastewater?

DR. SEDLAK: Title 22 is the California regulation that dictates what treatment standards are used. But they found over time was that water is pretty darn clean after it goes through filtration and disinfection.  So, it’s used for lettuce, strawberries, and full-contact crops.  It’s not restricted to forage for animals or things that necessarily get cooked or have peels, and the health effects studies have shown that it isn’t an issue.

In Israel, essentially all of the wastewater is used for agriculture, and they grow absolutely everything.  There are some concerns, though, because so much of the population eats food grown on the treated wastewater, such that there are magnesium deficiencies in the diet.  The dose of some pharmaceuticals that end up in certain foods reached levels that are at least at a screening level of concern and of interest to health professionals.  So, there are certainly some unresolved issues.

But to your larger question of whether we will ever use our treated wastewater to grow our food, there’s just not enough of it.  For each of us, our water footprint for agriculture is about ten times our water footprint for municipal use.  So even if we used all of our wastewater to grow all of our food, we’d only be at 10%.

One of the intriguing places we’ve started to look at is the idea of local agriculture and vertical farming using treated wastewater.  We’ve done some techno-economic analyses of housing developments like the Megabloks in Barcelona as an example of how you might repurpose the wastewater to grow fresh fruits and vegetables and generate a profit in the process.  And I think that’s intriguing because it’s local participation in the circular economy of water, which captures the imagination of the public.”

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