The Congo River is the world’s second-largest river system after the Amazon. More than 75 million people depend on it for food and water, as do thousands of species of plants and animals that live in the swamps and peatlands it supports. The massive tropical rainforest sprawled across its middle helps regulate the entire Earth’s climate system. The amount of water in the system, however, is something of a mystery. 

Hydrologists and climate scientists rely on monitoring stations to track the river and its connected water bodies as they flow and pool across six countries, and to measure precipitation. But what was once a network of some 400 stations has dwindled to just 15, making it difficult to know exactly how climate change is affecting one of Africa’s most important river basins. 

“To take action, to manage water, we need to know about our water resources,” says Benjamin Kitambo, a geologist with the Congo Basin Water Resources Research Center in Kinshasa, Democratic Republic of the Congo. “But we can’t know something that we don’t measure.” 

Researchers around the world are increasingly filling data gaps on the ground using information gathered from space. Satellites equipped with remote sensing instruments can peer into places where “in situ” measurements—those taken on site—are outdated, hard to gather, or kept private. 

Kitambo spoke by video call from Toulouse, France, where he’s conducting PhD research at the Laboratory of Space Geophysical and Oceanographic Studies. These days, he’s analyzing troves of satellite measurements and hydrological models to understand how the Congo River’s tributaries, wetlands, lakes, and reservoirs are changing. That includes studying records from more than 2,300 “virtual” gauging stations, which estimate two key metrics throughout the basin: “surface water height,” or the water’s level above a reference point, and surface water extent. 

He says most of the region’s field data dates back to before 1960, the year most countries in the region gained independence from European colonizers. Since then, research there has sharply declined, and collecting data on surface water has proved difficult. 

machine data on satellite image
Fritz Policelli and his team at Goddard Space Flight Center are creating maps like this preliminary one of the Ohio River by combining machine learning with data collected by the Sentinel-1 in order to track stream widths.NASA GODDARD SPACE FLIGHT CENTER/UNIVERSITY OF MARYLAND

About five years ago, the Congo Basin research center began installing a network of water-monitoring stations to address the “severe lack of basic knowledge” about the river’s main navigable channels, which often serve as roads. But some places in the vast basin were too remote or rugged for researchers to reach. In others, people removed the newly installed instruments to sell the materials, or because they feared being spied on.

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Many parts of the world face similar challenges. Countries in Latin America and the Caribbean have seen a “dramatic decline” in ground-based measurements since the 1980s, according to a 2018 assessment published in the journal Water Resources Research. In the Mekong River basin—which extends through six nations from China to Vietnam—countries closely guard their data on water availability, if they gather it at all.

Yet measuring water is key to helping people prepare for natural disasters and adapt to climate change, experts say. Rising global temperatures are projected to increase the risk of storms and flash floods in certain areas and severe drought in others. Meanwhile, massive infrastructure projects and sprawling urban development are altering and straining freshwater resources like rivers and lakes.

This need to know is driving a series of ambitious research initiatives using remote sensing tools. As the technology for gathering and analyzing data from space evolves, scientists are gaining a clearer picture of how water flows across Earth and circulates in the atmosphere.

Satellites observing

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By: Maria Gallucci
Title: How to measure all the world’s fresh water
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Published Date: Wed, 22 Dec 2021 10:00:00 +0000