This story was originally published by Yale E360 and is reproduced here as part of the Climate desk cooperation.
Makueni County, a corner of southern Kenya that is home to almost a million people, is a land of extremes. Nine months a year, Makueni is a hardened, sunburned place where crops struggle and plumes of orange dust wash down dirt roads. Twice a year, however, the province is ravaged by weeks of torrential rain, which drowns farm fields and turns roads into impassable bogs. “Water,” says Michael Maluki, a Makueni County engineer, “is the enemy of roads.”
Maluki’s axiom is true all over the world: Where roads and water cross, trouble follows. Roads cut off streams and bleed sediment; meanwhile, floods often erode road beds into muddy gullies. While rich nations are far from immune, these problems are worst in developing countries, where roads are largely unpaved and therefore particularly vulnerable to erosion. In Kenya and other nations, the problem is exacerbated by climate change, which has intensified the intensity of seasonal monsoons and droughts.
In 2019, Maluki began to think about how to reconcile two of his province’s challenges: the aridity of its dry season and the destruction of its wet season. That year, he and colleagues attended a local workshop led by a Dutch consulting firm called MetaMeta on the concept of “Green Roads for Water” – a set of guidelines for designing roads to transport water through strategic canals, culverts and dams catch and divert it for agricultural use. Inspired by the session, Maluki brought the idea to his colleagues and local farmers, who gave Green Roads their cautious blessing.
Makueni County’s Green Roads quickly proved their worth. Along the roads, Maluki’s team members installed “mitre drains” that channeled floodwater into newly dug canals that irrigated mangoes, bananas and oranges. They dug out farm dams, which stored the rainy season’s floodwater for use during drought, and they planted roadside fruit trees to absorb runoff and help control the dust blown up from unpaved roads. And where travel routes crossed ephemeral rivers at right angles, the province built levees—concrete road segments that also functioned as temporary dams. During seasonal floods, the drifts caught deep sandbars on their upstream sides. The sand retained pockets of water, which farmers tapped during the dry season via four-foot-deep wells dug upstream from the drift. In neighboring Kitui County, one study found that every $400 spent on similar low-tech adaptations increased farmers’ yields by about $1,000; according to Maluki, they also made the rainy season much less harmful.
Andrew Zakharenka
“The greatest asset for [the county government] in this program is the reduction of maintenance costs,” says Maluki. “It’s a two-way benefit.” He estimates that between 5 and 10 percent of the provinces roads now apply water harvesting principles.
Southern Kenya is not the only place to see such gains: Almost 20 countries have either implemented Greenways for Water or plan to start soon, and thousands of kilometers of roads, worldwide, have already received Greenways interventions. Engineers who took MetaMeta’s training have used its principles in Ethiopia and Bangladesh, and the concept is quickly spreading to places as diverse as Somaliland, Tajikistan and Bolivia. The idea has also gained traction with the World Bank and other international lending institutions, which are currently financing a road-building boom that promises to transform ecosystems and communities around the world. Green roads for water offer one potential path through these thickets of new construction, one that repositions roads as environmental assets as well as liabilities.
“By integrating these small and easy practices, you can have very big benefits,” says Anastasia Deligianni, manager of MetaMeta’s Green Roads for Water program. “We think this is a critical moment to really get it right.”
Green roads for water is the brainchild of Frank Van Steenbergen, a Dutch geographer and MetaMeta’s director. While working on irrigation projects in Pakistan in the early 1990s, Van Steenbergen first encountered “gabarbands,” stone terraces likely built by farmers millennia ago to catch water and soil from seasonal rivers during monsoons. The gabarbands were proto-dams, but their winding paths over ancient streambeds also reminded Van Steenbergen of roads, which tend to collect water along their surfaces. In the years that followed, he began to wonder: Why not use roads to direct and collect water in desirable places, rather than undesirable places?
The idea’s first major test took place in the Ethiopian state of Tigray. Each year, the region’s farmers participate in a weeks-long voluntary recovery effort known as “mass mobilization,” rebuilding terraces and cleaning irrigation canals. In 2015, the mobilization included the application of Green Roads principles. Among other things, Ethiopian farmers dug new trenches and dams and installed “floodwater spreaders” – low earthen berms that diverted road runoff to adjacent corn, wheat and barley fields.
Courtesy of MetaMeta
The results, says Kifle Woldearegay, a geoengineer at Ethiopia’s Mekelle University, have been dramatic. By 2018, so much water had infiltrated the soil around Tigray’s Greenways that the water table had risen about two meters, improving the productivity of adjacent farms by 35 percent. Woldearegay estimated that Tigray’s efforts have paid off almost $17,000 in agricultural and infrastructure benefits for every kilometer of road treated by the state — roughly a fourfold return on the government’s investment.
“Farmers were very happy,” says Woldearegay. “They see that moisture is retained in their fields and landscapes, and that their crops perform better.” Today, he says, virtually every road in Tigray is equipped with at least some water harvesting techniques.
Driven by their success in Ethiopia, van Steenbergen and a growing network of collaborators refined the Green Paths for Water prescriptions. The techniques tend to be amazingly simple. Soft earth ridges called crossbeams direct water off roads and into irrigation ditches. “Borrow pits” left after the excavation of gravel can be reused as rainwater collection ponds. In Bangladesh, engineers deployed fenced culverts to channel floodwater into rice fields. “It’s often very non-glorious things that make the difference,” says van Steenbergen.
Although MetaMeta coined the term “Green Roads for Water”, Van Steenbergen is adamant that no single entity owns the concept. MetaMeta does not hold any patents or license any technology; it simply conducts training and assessments, and it provides technical guidance to road construction agencies. Many of the techniques it promulgates have been developed by local engineers and farmers: for example, an Ethiopian drain design that could also apply to Yemen, or a Pakistani culvert with relevance in Tajikistan. “People are very creative,” says van Steenbergen. “These are all things that can easily be replicated.”
Since Greenways practices were coherent, the concept gained institutional support. The German NGO Welthungerhilfe has funded Green Roads training and construction in Somaliland; the Global Resilience Partnership funded assessments in Ethiopia, Kenya and Nepal; and the International Fund for Agricultural Development and the United Nations World Food Program organized events on the subject. In 2021, the World Bank hired MetaMeta to create a set of guidelines to outline the principles of Green Paths for Water and highlight successful case studies. The approach, says Kulwinder Singh Rao, the World Bank’s leading transport specialist, “offers a new way of thinking” about the relationship between roads and water. “Practitioners and policy makers in the road sector must embrace this new concept.”
Courtesy of Makueni County
The Green Roads movement is expanding in an era of unprecedented road building in developing countries. William Laurencean ecologist at James Cook University, has baptised the phenomenon of an “Infrastructure Tsunami” – a wave of construction that could produce more than 15 million miles of paved roads by mid-century and ten million miles of unpaved roads. This exploding transportation network could have tremendous benefits for human well-being. “Once there’s a road, there’s everything,” says Saroj Yakami, an engineer who heads the Green Roads movement in Nepal, where thousands of road miles has been built since 2015. “You can easily go to the hospital. You can get government services quickly. You can take your products to market.”
Yet this improved connectivity often comes at a high social and ecological price. In the Amazon, Laurance has found, the vast majority of deforestation occurs near roads; in Nepal’s Chitwan National Park, researchers have warned that roads will “cause a dramatic decline in tiger numbers” over the next two decades. According to Yakami, bulldozed Himalayan roads often leave wedges of spoil that absorb water and cause devastating landslides. “They take roads everywhere, and it’s not good for the environment,” he says.
In some cases, roads offer benefits and costs at the same time. According to Yakami, new Nepalese roads cut off mountain springs that had long sustained farms and households, but they also revealed springs that had long been buried. Left to flow, the degenerate springs turn dirt roads into unstable mudflats. But channeled in taps and pipes, they can become important water sources for villages stressed by drought. This approach differs from Green Roads strategies in Ethiopia or Kenya, where roads are primarily designed to capture rainfall rather than groundwater, but it similarly tries to synchronize road design with water delivery infrastructure.
But if roads can be recast as boons for water supply, will that framework provide a perverse incentive to build more of them? The idea that a road can be “green” seems oxymoronic: A large body of scientific literature shows that roads pollute air and water, fragment ecosystems, introduce non-native species and exterminate wildlife. In an email, Laurance expressed concern that “water harvesting could become a driver of road expansion in arid environments.”
Deligianni doesn’t dismiss those fears outright, but she doesn’t give them much credence. For one thing, most Green Roads for Water techniques have so far been applied as retrofits to existing roads, rather than incorporated into new ones. For another, she says, new roads are inevitable and, in many cases, desirable for local communities. So why not optimize the construction to come? “We look at the projections for the future, and so many roads are going to be built,” says Deligianni. “We’re just trying to change the narrative and add some benefits.”
For now, the Green Paths movement, for all its institutional momentum, is moving forward shakily. The idea, says the World Bank’s Singh Rao, requires “a paradigm shift in thinking and practice,” one that involves collaboration between agencies that tend to be in silos. In Ethiopia, Woldearegay says that ministries of agriculture are enthusiastic about Greenways and have incorporated them into their own technical guidelines, but road departments themselves have proved reluctant. “They don’t want the costs associated with design and implementation [them],” he says. This is the case in Kenya’s Makueni County, where limited budgets have hindered progress.
Yet these projects continue to attract attention: In recent months, Michael Maluki has given Green Roads tours to newspaper reporters, engineers and farmers from neighboring provinces. “We received so many visitors,” says Maluki. “The little things we do here make people notice.”
