Like the rivers of our planet arteries of our planet. They are woven into complex networks that carry life-supporting fresh water around the world. Not only are rivers our own livelihoods, providing us with the drinking water we need to survive, but freshwater reserves are also the primary lifelines of 10 percent of all known animals and half of all known fish species, helping to maintain healthy and diverse ecosystems. . In short, these are the most renewable, accessible and therefore sustainable freshwater reservoirs we have.
But humans have a surprisingly limited understanding of how much water Earth’s rivers hold and how fast that water moves; These two features are key to managing our planet’s precious freshwater resource.
Cedric DavidA scientist at NASA’s Jet Propulsion Laboratory (JPL) in California likens the situation to spending money from a checking account without knowing the balance.
Relating to: NASA’s SWOT satellite maps nearly all of Earth’s water (video)
“It was like we had an idea of how much we were making and how much we were spending, but we didn’t know how much was in the account,” he told Space.com.
Most of the existing literature on rivers refers to 50-year forecasts outlined in a report by the Russian Academy of Sciences, published in Russian in 1974 and later translated into English in 1978. This is probably because up-to-date estimates are difficult to collect. especially when it comes to rivers far from human population. Equal satellites It cannot monitor how much water flows from land into some rivers, known as runoff, which is water from precipitation lingering on the planet’s surface that exceeds the soil’s absorbing capacity. This excess water then flows into nearby water bodies, including rivers.
David told Space.com that it’s also difficult to determine river speeds based on traditional “back of the envelope” formulas based on in situ measurements from 50 years ago. In late April, David and a team NASA Researchers have embarked on a quest to provide the best estimates yet of how much water flows through Earth’s rivers, the rates at which it flows into the oceans, and how much both figures have changed. time.
“We’re able to repurpose some good old numbers with some tricks we didn’t even know were possible,” David said. “We did our best to correct whatever we could based on the limited observations we had.”
Using previous satellite data to model runoff levels for rivers on a map, researchers found that the total volume of water in rivers on Earth from 1980 to 2009 averaged 539 cubic miles (2,246 cubic kilometers); This is about half as much. Water volume of Lake Michigan. Stretching from the Andes Mountains in Peru to the Atlantic coast of Brazil, the Amazon River Basin contains 38 percent of all the water in the world. to workIt was published last month in Nature Geoscience. The same basin also discharges the most water into the ocean—about 1,629 cubic miles (6,789 cubic kilometers) per year, or 18 percent of the total discharge to the ocean worldwide.
“I was hoping to show myself that there is much more to river water than we think,” David said. “Apparently that’s not what we have; it’s a bit sobering.”
Covering 30 percent of the planet, the new data set consists of in situ measurements and computer models covering nearly 3 million river sections worldwide. It also brings to light rivers that are depleted due to human overuse. climate changeirrigation projects and other landscape-altering actions are likely affecting water supply in many rivers, including the Colorado River basin in the United States, the Amazon basin in South America, the Murray-Darling basin in Australia, and the Orange River basin in South Africa.
“We’re trying to give data so people can make smart decisions and start some conversations,” David said. To help this goal, the new dataset and study are open access, meaning anyone can read them online. “We hope this will make some difference,” he said.
He also noted the value of open science in aiding interesting scientific research as a whole.
The work that led to the new paper began in early 2022 when the study’s lead author, Elyssa Collins, came across publicly available code of a climate model that David had shared online. After working on the code for several months, Collins, now a doctoral student at North Carolina State University in Raleigh, reached out to David with a few ideas; It was an entrepreneurial effort that resulted in a six-month internship with David at the JPL location. In Pasadena, California. “This is just one of many success stories [of open science] “If you give something away for free, great things happen,” David said. “It’s important that we learn from each other, share, and include everyone who cares about the science we do.”
In the coming years, researchers plan to compare their latest predictions, based on computer models, with future satellite data from NASA’s Surface Water and Ocean Topography mission (SWOT) to improve estimates of the human footprint in our planet’s water cycle.
“You can think of it as camera views, but they just tell you the height of the water,” David said of SWOT data. By mapping the elevations of water surfaces on Earth since December 2022, the satellite helps scientists calculate changes in the height of the river and estimate how much water is available and how much water is draining from it. Last month the satellite captured a depth. temporary, shallow lake Germinated for several weeks at the bottom of Death Valley National Park, which spans the border of California and Nevada and is the hottest place on Earth. Soil. The 1-foot-deep (0.3-meter-deep) lake, called Lake Manly, spans more area than expected for such a body of water due to strong winds, allowing SWOT to examine events in an area without a permanent, dedicated area. instruments.
Other preliminary results suggest SWOT’s water elevation data may also fill gaps in the literature on evolving conditions during and after the floodSatellites that typically only image flooded areas are often unable to capture and recover flood forecasts.
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In addition to SWOT, 30 NASA satellites is currently recording data on Earth’s land surface, ice, oceans, and atmosphere. They are there as part of an effort the agency began in the 1980s; an effort to collect the data necessary to understand and predict weather, as well as an effort dedicated to tracking hurricanes, floods, wildfires, and other catastrophic changes to the planet’s structure. Climate made worse by human activities such as burning coal. These satellites, which provide us with images of the Earth at scales that can never be obtained on the ground, help scientists observe the Earth. Animals vulnerable to habitat lossto call signs of potential volcanic eruptionsdecode changing chemistry of coastal waters and follow their rates decreasing sea ice.
“It’s relatively underappreciated how much effort we put into Earth science at NASA,” David told Space.com. In fact, he said, half of the science done at JPL is Earth science.
“We don’t have Planet B; it’s been that way for a long time.”