In the world of water, 2021 was yet another year for the record books. Parts of Western Europe reeled from deadly floods that sent rivers surging to levels not seen in 500 to 1,000 years. Destructive floods hit central China as well, displacing more than a quarter of a million people from their homes. Meanwhile, a large swath of the southwestern United States remained locked in a megadrought—the second-driest 20-year period in 1,200 years.
One might think that the impressive water engineering installed in the US and elsewhere over the last century would safeguard society from such catastrophic events. Globally, some 60,000 large dams now capture and store water, allowing engineers to turn rivers on and off like plumbing works. Each year, the world’s cities collectively import the equivalent of 10 Colorado Rivers through vast networks of pipelines and canals. And thousands of miles of artificial levees protect cities and farms from flooding rivers.
In many ways, it’s hard to imagine our world of nearly 8 billion people and $85 trillion in annual goods and services without this water engineering. Cairo, Phoenix, and other large desert cities could never have grown to their present sizes. California’s sunny Central Valley would not have become such an abundant producer of vegetables, fruits, and nuts.
Yet when it comes to water, the past is no longer a good guide for the future. The heating of the planet is fundamentally altering the water cycle, and most of the world is unprepared for the consequences.
One of the most alarming wake-up calls came in 2018, when the city of Cape Town, South Africa, was nearly forced to shut off the drinking water taps of 4 million residents. Three consecutive years of drought had dried up its reservoirs. City officials began publicly announcing “Day Zero”—the date water would no longer flow to household faucets.
Tempting as it might be, the solution is not to further bend nature to our will by building bigger, higher, and longer versions of water-engineering infrastructure.
Conservation measures helped Cape Town push Day Zero further out—and then, luckily, the rains returned. But no city wants to rely on luck to bail it out of disaster. Scientists later determined that climate change had made Cape Town’s extreme drought five to six times more likely.
Droughts, floods, and other climate-related disasters come with big price tags. In 2017, three large hurricanes in the US were the primary cause of a record $306 billion in damages, more than six times the yearly average since 1980. While 2017 appears to be an outlier, climate scientists expect annual disaster costs of that magnitude to be common by the end of the century.
Tempting as it might be, the solution is not to further bend nature to our will by building bigger, higher, and longer versions of water-engineering infrastructure. It is to work more with natural processes, rather than against them, and to repair the water cycle, rather than continue to break it. Along with water-saving measures, such approaches can create more resilient water systems. They can also help solve our interconnected water, climate, and biodiversity crises simultaneously and cost-effectively.
As floods worsen, for example, instead of raising the height of levees—which often intensifies flooding downstream—we can consider ways to strategically reconnect rivers to their natural floodplains. In this way, we can mitigate floods, capture more carbon, recharge groundwater, and build critical habitat for fish, birds, and wildlife.
The Netherlands, a country renowned for its advanced water engineering, avoided major damage from the historic floods in July 2021 thanks to its new approach to flood control, which gives rivers room to spread out during flood events. The Maas River, which flows in from Belgium (where it is called the Meuse), broke its 1993 high-flow record last July, but it caused less damage than that earlier flood. One reason was a recently completed project that diverted floodwaters into a 1,300-acre wetland, which held the water and lowered parts of the raging Maas by more than a foot. The wetland also sequesters carbon and doubles as a nature preserve, offering valuable climate and wildlife benefits as well as recreation opportunities. Through its “Room for the River” program, the Dutch are implementing these nature-based flood control projects at 30 locations around the country.
Napa County, California, took a similar approach when redesigning its flood-control system for the Napa River. In the early 1900s, engineers straightened and deepened the Napa’s channel and filled in its wetlands and tidal marshes. After the area endured 11 serious floods between 1962 and 1997, local officials asked the US Army Corps of Engineers to collaborate on a “living river” strategy that would reconnect the Napa with its historical floodplain, move homes and businesses out of harm’s way, revitalize wetlands and marshlands, and construct levees and bypass channels in strategic locations. Residents voted to increase their local sales tax by half a cent to pay their share of the $366 million effort. In addition to gaining new trails for birding and hiking, the city of Napa has benefited from more than $1 billion in private investment that revitalized the downtown.
In an effort to scale nature-based systems, the US Congress directed the US Army Corps of Engineers in 2020 to consider them on equal footing with more conventional infrastructure. A significant shift in approach, however, will likely require changes in Corps rules and procedures, as well as additional funding.
Agricultural practices that rebuild soil health offer another strategy. Globally, soils can hold eight times as much water as all the world’s rivers combined, but we rarely think of soils as a water reservoir. Scientists have found that boosting organic matter in the soil by one percentage point can increase the soil’s water-holding capacity by up to 18,000 gallons per acre, creating resilience to both intense rains and dry spells.
This means farmland practices that regenerate soils, such as the planting of cover crops during the off-season, can not only boost yields and lower costs but improve water management and mitigate climate change. As an added bonus, cover crops reduce farm runoff, which means less nitrogen and phosphorus polluting rivers, streams, and aquifers. That, in turn, means fewer of the toxic algal blooms that threaten drinking water, coastal fisheries, and inland lakes around the world.
New policies and incentives that recognize the interconnections between climate, water, and agriculture are needed to expand the use of such nature-based solutions. The state of Maryland, for example, shares the cost of planting cover crops with farmers. Some 29% of the state’s farmland gets planted in cover crops, compared with about 6% of US farmland overall.
Holistic solutions don’t come easily, since they require thinking and acting outside of bureaucratic and professional silos. But they are key to a livable future.
While it is too late to avoid the impacts of climate change, we can avoid the worst of those impacts by investing more heavily in such nature-based water solutions.
Sandra Postel is the author of Replenish: The Virtuous Cycle of Water and Prosperity and the 2021 Stockholm Water Prize Laureate.