In the not-so-distant future, even those of us who take for granted that a turn of a tap will produce a flow of water may be faced with the problem one billion people in arid and semiarid regions already experience: no clean drinking water.
While we do live on a water-covered planet, only 3 percent of that water is fresh. That supply is found in glaciers and ice, in rivers and lakes, and below the ground. Groundwater, the source we depend upon for drinking, producing food, and cleaning, is being depleted and polluted, and climate change, the force that governs where and when water is available, is conspiring to shrink fresh water supply worldwide.
“We are in the middle of a dramatic global water crisis that is silently progressing,” warns Upmanu Lall, the Alan and Carol Silberstein Professor of Earth and Environmental Engineering and director of the Columbia Water Center, a unit of the Earth Institute that Lall helped found in 2008. “While climate change is expected to exacerbate these problems in many places in the world, our current use pathway leads to perhaps the most significant resource sustainability problem that humanity faces today. The recognition of this challenge is still limited, since people think about water place by place rather than by what is happening globally.”
To find a fix, Lall is tackling water sustainability on multiple fronts: hydrology, climate dynamics, water resource systems analysis, and risk management. He has spent a career honing his expertise in statistical and numerical modeling of hydrologic and climatic systems, and water resource systems planning and management. The outcome has resulted in pioneering statistical methods and their application to the prediction of hydrologic and climate conditions, and advanced tools for decision analysis and risk management.
How does math and modeling help with sustaining a natural resource like water? Consider Lall’s statistical prediction model for river flow in northeast Brazil.
“The wet season there is January through May, and we can forecast the water that will be available in that season in the previous July. Our novel algorithm uses as predictors Atlantic and Pacific Ocean climate conditions that were identified as potential important determinants of the January–June climate,” Lall explains.
The model’s accuracy is comparable to what other models achieved in December, just before the start of the wet season. Having the information six months earlier helps in decision making to allocate water in the regional reservoirs to minimize loss due to evaporation and spillage, provide water or save water in anticipation of the future conditions, and improve the area’s economic performance relative to what would be expected in a cycle of severe droughts in the region.
“Nearly four million people, plus farms, industries, and cities are served by the systems in which we put this forecasting and decision-making system in place. In effect, we have created a system for adaptation to a changing climate in one of the most extreme climate regimes in the world,” he says.
Lall, who has a joint appointment in Civil Engineering and Engineering Mechanics, also tackles understanding extreme weather events that impact water supply, such as flooding. By studying the mechanisms of extreme floods and how they can be identified from data and climate models, Lall and his team are working to better predict the risk of floods in the face of the world’s changing climate.
“We have identified that moisture transport from tropical oceans to land is a primary factor in determining extreme floods and are building models to understand the factors that lead to connecting specific moisture sources to specific locations with flood potential,” he says.
This global view is expected to lead to answers about why floods happen at roughly the same times in different parts of the world and how to predict that impact. This science could help relief organizations to better prepare to meet needs, and businesses and flood-prone countries to better manage supply chains.
Lall’s research has yielded some surprising outcomes. “The big surprise is that improving water use efficiency in agriculture is eminently feasible and could, by itself, solve much of the global water stress,” he says. This would require shifts of crops to better match climate and water availability, precision irrigation technologies that improve productivity while reducing water use, and climate forecasts that lead to better use of reservoir and groundwater storage. Those are all achievable, Lall says. But perhaps the biggest change needed, he says, is one that is contentious for people who take water resources for granted.
“Right now, water is a high-value commodity at a very low price,” he explains. “We need to price water better so there are incentives for everyone to adopt better use practices.”
—by Amy Biemiller