NASA Data, Trainings Help Uruguay Navigate Drought

Lee esta historia en español aquí.

NASA satellite data and training helped Uruguay create a drought response tool that its National Water Authority is now used to monitor tanks and guide emergency decisions. A similar approach could be applied in the United States and other countries around the world.

From 2018 to 2023, Uruguay has known its worst drought for almost a century. The capital of Montevideo, which houses nearly 2 million people, has been particularly affected. In mid-2023, Paso Severino, the largest reservoir and the main source of water for Montevideo, fell just 1.7% from its capacity. As the water levels decreased, government leaders have declared an emergency. They started to identify the backup supplies and asked: there was water left in other upstream tanks – mainly used for livestock and irrigation – which could help?

It was then that the environmental engineer Tiago Pohren and his colleagues from the National Water Authority (Dinagua – Ministry of the Environment) turned to data and training of NASA to build an online tool that could help answer this question and improve the monitoring of the country’s tanks.

“Satellite data can inform everything, to plan irrigation in large plains to water quality management in Chesapeake bay,” said Erin Urquhart, director of the NASA water resources program in Washington. “NASA provides the reliable data necessary to meet water attacks all over the world.”

The Dinagua team learned NASA’s resources during a workshop in 2022 in Buenos Aires, organized by the Interagentic Team of Sciences and Applications (ISAT). Led by NASA, the US Army Corps of Engineers and the American State Department, the workshop focused on the development of tools to help manage water in the La Plata river basin, which extends over several South American countries, including Uruguay.

During the workshop, NASA researchers introduced participants to methods of measuring water resources in space. The NASA applied remote sensing program (ARSET) has also provided an introduction to remote sensing principles.

“NASA does not only provide data,” said John Bolten, NASA principal scientist for Isat and chief of the hydrological science laboratory at the NASA Space Flight Center in Greenbelt, Maryland. “We collaborate with our partners and local experts to translate data into useful, usable and relevant information. This type of coordination is what makes NASA water programs so effective in the field, in the house and worldwide. ”

The Dinagua team has brought ideas and provided guidelines to Pohren for a tool that applies Satellite Imaging Landsat and Sentinel to detect changes in Uruguay reservoirs. Landsat, a joint mission of the NASA-US geological survey, provides decades of satellite imaging to follow changes in earth and water. The Sentinel missions, part of the Copernicus Earth observation program to the European Commission and operated by the ESA (the European Space Agency), provide visible additional, infrared and microwave images for surface water assessments.

From a young age, Pohren knew the challenges related to water, because the floods have repeatedly flooded the houses of his relatives in his hometown of Montenegro, Brazil. It was an additional motivation for him when he traveled Arset tutorials and learned to write computer code. The result was a monitoring tool capable of estimating the surface of Uruguay’s tanks over time.

The tool is based on several techniques to differentiate the extent of the surface water from the tanks. These techniques include three optical indicators derived from the Landsat 8 and Sentinel-2 satellites:

• Normalized difference water index, This highlights water by comparing the amount of green and close infrared light. The water absorbs infrared light, so it stands out clearly from the earth.
• Modified normalized water index, which exchanges close infrared with short wave infrared to improve contrast and reduce errors during differentiation between water and vegetated or vegetated areas.
• Automated water extraction index, which combines four types of reflected light – green, close infrared and two infrared strips with short waves – to help separate water from shadows and other dark characteristics.

In 2023, the Dinagua team used the Pohren tool to examine the reservoirs located upstream of the drinking water supply of Montevideo. But the data told a difficult story.

“There was water available in other tanks, but it was a very small quantity compared to the water demand from the Métropolitan region of Montevideo,” said Pohren. Simulations have shown that even if all the water was released, most would not reach water consumption for Montevideo or the Paso Severino tank.

Despite this news, the analysis prevented actions that could have wasted significant resources to maintain productive activities in the upper basin, said Pohren. Then, in August 2023, the rain began to fill the reservoirs of Uruguay, allowing the country to declare the end of the water crisis.

Although the immediate water crisis has passed, the tool that Pohren has created will be useful in the future in Uruguay and in the world. During an ISAT workshop in 2024, he shared his tool with international water resources managers in the hope that this could help their own efforts to response to drought. And Dinagua officials still use it to identify and monitor dams, irrigation tanks and other water bodies in Uruguay.

Pohren continues to use NASA training and data to advance the management of tanks. He currently explores Arset training on the way in which the mission of the topography of surface waters and the ocean (SWOT) will further improve the system by allowing Dinagua to directly measure the height of the water in the tanks. He also follows the new NASA joint mission with the ISRO (The Indian Space Research Organization) called Nisar, which was launched on July 30. The Nisar satellite will provide radar data which detects changes in the extent of the water, regardless of the cloud cover or the time of the day. “If a drought will happen again,” said Pohren, “with the tools we have now, we will be much more ready to understand what are the conditions of the basin and make predictions.”

By Melody Pederson, Rachel Jiang

The authors want to thank Noelia Gonzalez, Perry Oddo, Denise Hill and Delfina Iervolino for the support of the interview as well as Jerry Weigel to connect with Tiago about the development of the tool.