Sandra Postel: How We Can Replenish the Water Cycle to Help Farmers and Protect Our Water

Caption Sandra Postel

Courtesy of Sandra Postel.

For centuries humans have channeled water to create a prosperous, modern society.

Whether it's irrigating fields for food, constructing massive dams for water storage or building water treatment plants for clean water, there is a long history of intervening in the natural flow of water.

But has human intervention in the water cycle gone too far?

Sandra Postel wades into this question in her most recent book, Replenish: The Virtuous Cycle of Water and Prosperity. Sandra is a water expert, director of Global Water Policy, Freshwater Fellow of the National Geographic Society, and prolific author of many books and articles on water and the environment, who has served in many other roles and garnered many achievements. In 2017 the Change the Course campaign, which Sandra co-created, won the US Water Prize for returning billions of gallons of water to dwindling rivers and wetlands. 

Sandra explores the tremendous effort we have put into controlling water and finds that we might have reached a point where the downsides can outweigh the advantages, especially as we confront climate change impacts. As we contend with droughts that wither crops and floods that inundate city streets, she searches for better ways to replenish and restore the water cycle. This means working with nature to store water in healthy soils and to revive watersheds to maintain clean water and healthy ecosystems.

Read on for an interview with Sandra about ways farmers, water managers and consumers can unite to replenish the water cycle.

In an attempt to control water, you suggest that humans have broken the Earth's natural water cycle. What are some of the big problems and solutions that you want to address in Replenish?

The breaking of the water cycle and how we can fix and replenish it is really the theme of the book. For example, groundwater is a very big concern for water security now and into the future. I've been tracking what's going on with groundwater pumping for more than 20 years now and it has gotten much more severe as a result of significant and extended droughts in some of the most important food producing regions of the world.

And thanks to the great NASA satellite program that ran for years but recently stopped - the GRACE program [no relation] - we better understand what's going on with groundwater depletion and found that it's more significant than we might have realized. Thankfully there will be a follow-on satellite mission.

So this is a big problem with our future water security because groundwater is where you want to go in times of drought when the surface water supplies dry up, when rivers are running low because you haven't had the rain and snow melt, or when reservoirs are shrinking for the same reason - you need to be able to go underground and tap that groundwater as a reserve for those dry times. If you've already been over-pumping groundwater, then you're going to go into significant depletion and it's going to be very hard to recover from. That's what we've seen in California during that extended five-year drought. We've seen it in the Colorado River Basin, which has been more or less in drought for 16 or more years, with last year being a bit of an exception. Of course, the important Ogallala Aquifer in the American High Plains is being drawn down; just as many other parts of the world are having water problems.

ReplenishReplenish by Sandra Postel

One of the examples I talk about in the book is the active replenishment of groundwater in California, which finally passed a state groundwater law in 2014. Even though many thought the goals were far into the future, in the year 2040, California needed to find a better balance of groundwater pumping and recharge with goals to make sure things are happening. With a El Niño year upon the state, scientists saw an opportunity to try out this idea of taking winter time flood water and basically flood farm fields, almond orchards and other annual crops, as well as perennial crops, to see if that would be an effective way to recharge without damaging the roots of the plants or trees, without damaging water quality because we want to recharge groundwater through farmland and without diminishing yield. So it was a combination of a recharge and science experiment to see if this could be done.

What can be done to improve farming and land management to build soil health, particularly as it affects large swathes of farm land?

I spend a chapter on soils, and I have to say that this is a part of the water cycle I had spent too little time researching and studying. I had talked in my past work about ways to get more water into the soil and efficient use of irrigation water to get water into the root zones of crops more efficiently. But the soil is a reservoir itself, which is very important to think about. The numbers suggest that soils are capable of holding eight times as much water as all the world's rivers combined. And yet, you don't really think of soil as a water reservoir, and how it sets up the water cycle. So over time the diminishment of soil fertility, the compaction, the loss of nutrients and organic matter in the soil from the kind of heavy industrial agriculture we've seen - so much of our farmland areas have taken away that soil reservoir. We're not getting that water stored.

But the soil is a reservoir itself, which is very important to think about. The numbers suggest that soils are capable of holding eight times as much water as all the world's rivers combined.

I've been really interested in all these interesting ways, from no-till agriculture to cover cropping, that restore soil fertility and expand that soil reservoir to create more opportunities to mitigate drought. Research suggests that even increasing organic carbon in the soil by one percentage point, so going from say three percent organic matter to four percent organic matter, you might store an extra 18,000 gallons of water per acre. In a time of drought, that is then potentially significant in building resilience.

This is a non-partisan issue for farmers in the heartland of this country to build resilience against drought. Yet our farm policies -the Farm Bill and the farm subsidies that we have - do not encourage this. Only about three percent of US farmland gets cover cropped, and cover cropping is one of these things that helps to reduce the nitrogen runoff that's polluting our rivers and lakes and creating dead zones. It helps to reduce erosion and it can expand that soil reservoir by rebuilding soil fertility. All these benefits and yet we've only got about three percent of our farmlands getting cover cropped. So that's a ripe area for policy incentives to encourage what seems to be a really clear way of getting multiple benefits from a change in how we farm.

Human civilization was built harnessing water for its own ends, particularly for water management and farm irrigation. But are we at a point where contemporary society and industrial agriculture has to change its ways of operating to create resilience while confronting water and climate-related disruptions?

As a whole, over the last century we've taken a command and control approach to water management by building the dams, the levies and the canals to move it around. It's hard to imagine the society we have today globally, 7.5 billion people and $80 trillion in economic activity every year, without all this water engineering. But I think we're at a point now where more of the same is not going to serve us as well, in part because climate change: the intensity of our weather extremes are increasing. We're going to have to think differently.

I think it's that shift in mindset to look at nature as a partner rather than as something to continue to command and control. Nature has these amazing services, whether it's wetlands and their ability to store and cleanse water, and watersheds and their ability, when healthy, to mitigate the ramifications of fire on downstream water systems, on and on. Looking to nature as part of the solution rather than something to continue to control is key. Again, healthy soils are another good example, so that restoring soil more of their natural fertility will be helpful in mitigating floods and droughts. So I think that's the direction we need to go. Let's bring ecology into the picture. Let's bring nature in to the solutions and bring those ideas around the table and look at how we can get smarter, get more creative with what nature offers.

It's less expensive to do many of these things if you bring nature's services into the solution. We see over and over again with watersheds where $1.7 billion invested in protecting Catskill-Delaware Watersheds helped to avoid a $10 billion water filtration plant for New York City's drinking water. But it's not easy to do and it takes work to keep those benefits and partnerships going.

In your chapter, Clean It Up, you cover the mounting threat of dead zones and harmful algal blooms caused by nutrient pollution from agricultural runoff, septic systems and other sources. What are some ways we can come to grips with these problems?

If you look at the Upper Mississippi River Basin, for instance, this is a very important agricultural area. We've cleared, drained and lost, through conversion of land uses, about 35 million acres of wetlands in the Upper Mississippi River Basin and converted most of it to farmland. Wetlands are tremendous ecological assets for floodwater storage as it releases it gradually back to rivers and groundwater, and takes the pollution out of that water so that it naturally reduces nitrogen and phosphorous loads. Losing all those wetlands means that we now have more runoff carrying those pollutants into our rivers and streams. That is part of the reason we have this big dead zone in the Gulf of Mexico every year.

Studies have been done over and over to show that if you can strategically restore wetlands or rebuild wetlands in critical locations you can cut down those nitrogen and phosphorous loads into our rivers and streams. And you're starting to see where downstream utilities have to deal with heavy loads of nitrogen and end up having to invest in more treatment facilities to handle that nitrogen. Well, what about dealing with an upstream and creating the incentives for farmers to do this?

There are some real unique partnerships already happening but we need to scale it up. This should be something that we're encouraging on a national scale through policy. It's a national problem and so I think it's a doable thing, but we have to shift the incentives. The last figure I've seen in taxpayer dollars for farm subsidies, about one dollar is going to conservation efforts for every 500 dollars going to crop subsidies. Let's just shift that and get some more public benefit out of these subsidies and create benefits for society at large and for the security of our drinking water. We've got a ways to go as we keep pushing back bold steps needed upstream.

Water footprints, especially for food, are becoming better understood. What value do you think the water footprint concept has for researchers, policymakers, consumers and society at large in the service of developing a water ethic?

Water footprints are great for bringing what can seem like abstract water issues right down to the personal level. Water is one of those areas where we're accustomed to leaving it to the engineers who will provide the irrigation water so that our wheat is grown, deliver water to our treatment plants then make sure it comes out of our taps at home, and we haven't had to take responsibility for it. In some ways we've had so much success with these water systems, and we grow this amazing amount of food and in wealthier countries we do, generally speaking, have the incredible luxury that every time we turn the tap, clean water does come out.

But we now have a situation where we're in a net depletion state in so many areas and we're losing rivers and wetlands, and our consumption is really taxing our water systems. And so I think raising awareness about what each individual's daily life consists of with regard to pressures on water is a really good step for allowing the individual to engage and feel like they can make a difference.

I consider diet very personal and so I never get preachy about diets. I'm educating about how much water it takes to make various things and, for example, all beef burgers are not equal - it depends on how the cattle were raised. Sometimes cattle can be raised in ways that are good for habitat and good for the environment. So I think that educational process and understanding our personal choices around our consumption can be empowering and permits us to feel like on an individual scale, we can be part of the solution. In the wealthier countries, where our water footprint here in the United States is twice the global average, we have a responsibility to look at our consumption habits and then make some choices we feel would be important and good to make in our individual lives so that we can all feel like we're doing something.

On the corporate side it's becoming more and more important for the business community to understand not just the water use within their four walls, say a factory, but also to look extensively at the supply chain. This is very often done, especially in the food and beverage part of the industry, by monitoring how the raw materials, usually crops, are grown and improving the efficiency and sustainability of the whole supply chain. This is very important and more companies are coming to that conclusion and acting on that as well, which is very positive.

You've traveled the world and seen numerous examples of human intervention throwing the water cycle out of whack. At the same time, you have been on the forefront of developing the case for a "water ethic," in which people respect water as a precious. What gives you hope amid all the difficulties?

There are many big problems, like the threat of biodiversity loss in freshwater habitats, which can make it hard to be optimistic. This can make us despairing when we see that the water cycle is broken and that the scale of the challenge is so great. I use to be more of a person who thought, "If we just get the policies right, everything will follow." Now I really believe we need to have stories on the ground that inspire and motivate, and then have policy makers look at those and say that we should be doing more of what works. It's good to see that real change is doable, and then learn from those examples and scale up to make it happen. And then these policy changes will hopefully come.

The Verde Valley was a unique collaboration built on trust, not necessarily driven by policy, and that kind of a project is a win for everybody. The irrigators lost nothing and they got an upgraded system. They got the water they needed while giving some to the river as well.

I think these positive stories on the ground, like examples of ranchers working with conservationists, are very inspiring to people and make us feel like, "Yeah, we can do this in our part of the world, too, just like what was done over there." We need to be working at both of those levels [on-the-ground and policymaking] at the same time. Look what the policies are that would have to be shifted and reformed in some way to allow these things to scale up. Many of these examples and stories in Replenish are ones where they're almost working against the odds and show that existing policy doesn't really inspire this kind of a project. But a unique partnership, a new law that hasn't been exercised yet, whatever it is has allowed this to happen and isn't necessarily the natural way of things given existing policy, particularly with water in the Western US.

Take the interesting Verde River [Arizona] example in the book. Western water, as everyone knows, most especially in the farming community, is "use it or lose it." You don't necessarily want to get smarter about how you use water because if you showed you need less, you risk losing some water rights. So here was a unique partnership in the Verde Valley, with irrigators and a conservation community spearheaded by the Nature Conservancy of Arizona. The building of trust allowed this technology to come in and redo how that 150-year old ditch system was operated so that you get a healthier river, and better habitat for birds, fish and wildlife. In Western landscapes, these rivers are a lifeline. This is where the birds have to go. This is where wildlife have to go. And if you've got a depleted river then that's just bad for life in the region. The business community came in to help support this with money that was needed to install these technologies.

The Verde Valley was a unique collaboration built on trust, not necessarily driven by policy, and that kind of a project is a win for everybody. The irrigators lost nothing and they got an upgraded system. They got the water they needed while giving some to the river as well. Urban wildlife habitats and recreational opportunities improved, and so the economies of the local towns in the Valley improved because they got the water they needed and more recreation and tourism business coming in. So it's hard to find a downside and that's the type of thing I'm hoping Replenish will inspire more of, and policymakers can take a look at it.

This interview was edited for clarity and brevity.