In new study, satellites measure evaporation in 164 large reservoirs around globe

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NASA collaborated with Ph.D. student Deep Shah, research scientist Dr. Shuai Zhang and their faculty advisor Dr. Huilin Gao, professor in Texas A&M University’s Department of Civil and Environmental Engineering, on research focused on the development of a Global Water Reservoir (GWR) product.  

The primary goal of the research team was to ensure data continuity between Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Suite (VIIRS), tools found in satellites that monitor reservoirs. Their work was recently published in the Nature sub-journal, Scientific Data. 

Accurate water monitoring data not only aids water resource management but also policy decision-making. Satellites carrying MODIS have served this function for the last 24 years and satellites carrying VIIRS have had a newer version of the technology since 2011. 

“We want to use this overlapping period to identify whether we can use VIIRS after MODIS is decommissioned,” Shah said. “From 2000 to 2012, we used MODIS observations, and from 2012 to 2021, we used VIIRS observations. Then we merged data from both sensors and compared them to MODIS observations from 2000-2021 to see if trends remained constant.” 

Previously, satellites measured lakes and reservoirs only by their size and water volume. This study introduces the practice of measuring water loss through evaporation, offering a more complete picture of the dynamics associated with water resources.  

“These product developments were originally based on a paper I wrote over 10 years ago,” Gao said. “For instance, 10 years ago, there were 34 reservoirs, but we continued increasing the numbers, variables and accuracy in this product.” 

The recent work presents an open-access, operational dataset detailing area, elevation, storage, evaporation rate and evaporation volume for 164 large reservoirs globally, including 151 man-made reservoirs and 13 regulated natural lakes. Their research offers valuable data for environmental research and water management.