NASA Study Unveils Global River Water Audit

Researchers at NASA's Jet Propulsion Laboratory (JPL) in Southern California have made a significant breakthrough in understanding global river water volume. They found that the average global river water volume from 1980 to 2009 was about 539 cubic miles, which is approximately half of Lake Michigan's water capacity. Despite representing just 0.006% of all freshwater on Earth, rivers play an essential role in human civilization. 
 
Cedric David, a co-author of the study and researcher at JPL, described the difficulties encountered when attempting to quantify river storage and flow. He likened it to "spending from a checking account without knowing the balance." Population growth and climate change are exacerbating these uncertainties. 
 
Despite these challenges, David emphasized that understanding our 'water balance' is fundamental for effective management strategies. The task becomes increasingly crucial as we grapple with issues like population growth and climate change. 
 
The research also anticipates that data from the Surface Water and Ocean Topography (SWOT) satellite will soon refine these estimates further. Launched in December 2022, SWOT aims to map global water elevations—information vital for assessing human impacts on the water cycle more accurately. 
 
Several regions emerged as critical areas regarding their river storage capacities or depletion due to human activities during this study. Notably, the Amazon basin holds around 38% of total global river storage—approximately 204 cubic miles of water—while also discharging most into the ocean annually. 
 
However, certain areas, such as parts of the Colorado River Basin, have less outflow than inflow, suggesting heavy usage by humans and unsustainable practices may be prevalent there. 
 
Elyssa Collins led this innovative research while interning at JPL alongside her doctoral studies at North Carolina State University. She stated, "These are locations where we're seeing fingerprints of water management," highlighting how their findings could guide future resource allocation decisions. 
 
To create an accurate picture worldwide concerning rivers, the team combined gauge measurement data with simulations from three different land surface models. This approach helped reconcile any discrepancies between observed and estimated water flows. 
 
They created a high-resolution global map of rivers using elevation data and satellite imagery, including images from NASA's Shuttle Radar Topography Mission. Collins emphasized that this new methodology could reveal where, globally, most river water is stored or discharged into oceans. 
 
Collins, now a postdoctoral researcher at the University of North Carolina at Chapel Hill, explained: "That way we can see where in the world the most amount of river water is stored or where the most amount of water is being emptied into oceans from rivers." 
 
The research by JPL highlights how crucial it is to understand our 'water balance' for effective management strategies. It also emphasizes that technological advancements such as SWOT satellites will play an essential role in refining these estimates further, leading us towards more sustainable practices concerning our precious freshwater resources.