How satellite technology can protect the world's drinking water

River experts say new satellite technology holds the promise of protecting water quality around the world.

Rivers can be difficult to study because many of them are inaccessible. Even identifying them is a challenge since many rivers are bone dry for months or even years.

“Rivers, especially small streams, are very hard to define. They are variable and can be intermittent,” said Dongmei Feng, a professor of environmental engineering at the University of Cincinnati.

In a paper published in the journal Nature Water, hydrology experts from around the world explained how scientists can use new tools such as satellite remote sensing to study water quality and the health and stressors of all of the world’s rivers.

Feng said rivers are a vital part of the planet, connecting oceans, the atmosphere and landscapes. Rivers propelled human civilizations around the world. Even today, 90% of the world’s population lives within 6 miles of a river. People are still hugely dependent on them for survival. They are the primary source of drinking water for cities around the world.

“Every major city has a river that defines it. Rivers provided the essential resources that allow cities to grow,” she said.

Researchers can use satellite remote sensing to track how rivers affect the world’s oceans as sediment and nutrients get carried into estuaries, essential nurseries for fish and other marine life.

“In the paper, we advocate for the idea that rivers should be studied at a global scale and individually,” Feng said.

“Every river is unique, defined by its distinct climate, surrounding environment and human footprint,” she said. “That’s why we want to study each at scale.”

Co-lead-author Xiao Yang from Southern Methodist University said new satellite technology allows researchers to monitor water quality using changes in the spectrum of light, which can identify the nutrients in the water. Satellites and computer modeling hold the promise of tracking water quality in extraordinary global detail.

“This will be an ambitious goal but will be well worth the effort,” Yang said.

Feng is an expert in this field, earning a doctorate in hydrological modeling and remote sensing. She said she is excited about the prospects of learning more about rivers.

“You never know until you study it. Satellite remote sensing provides a powerful means to achieve this,” she said.

Feng was awarded a National Science Foundation early career development grant of approximately $800,000 this year to study the nutrient dynamics in rivers that can lead to toxic algal blooms. This phenomenon can shut down water treatment plants and disrupt boating, swimming and other recreation. 

Toxic cyanobacteria in the algae can harm human health, leading to rashes, nausea and even liver or neurological damage. Treating water containing toxic algae requires an expensive multistep process.

Feng plans to study 50 years of data on the world’s rivers to learn more about how they carry nutrients and what that can teach us about developing early warnings for toxic algae blooms. When too many nutrients from fertilizers or sewage get into the water, it creates a smorgasbord for algae that begin reproducing wildly.

The floating algae blocks out sunlight, killing other aquatic plants. And when the algae die, bacteria that feed on all that dead plant matter consume oxygen in the water, creating dead zones that can lead to massive fish die-offs. This deadly cycle is called eutrophication.

“We can learn a lot by studying nutrient dynamics. At least 40 % of U.S. rivers have issues with nutrient pollution,” she said.