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Wednesday, 04 September 2013 08:32

Satellite technology key to mapping global water resources


Satellite and sensing technology is becoming key to mapping global water resources and now forms an essential and rapidly growing part of water resources management.

In a new initiative, the World Resources Institute Aqueduct project team, which is focused on measuring, mapping, and understanding global water risks, are now working with researchers on the Gravity Recovery and Climate Experiment (GRACE) project to incorporate new groundwater data onto Aqueduct’s interactive water maps and global water risk assessment tool.

The GRACE project consists of twin satellites that, from space, track changes in groundwater by detecting shifts in gravity. Approximately 200 miles above the Earth’s surface, the two satellites circle the planet, always between 106 and 193 miles apart.

Over the past 11 years GRACE has created a unique picture of groundwater level changes around Earth which is already helping water users and policymakers manage scarce groundwater resources in California, the Tigris-Euphrates Basin and several other locations around the world.

The satellites play a key role in providing transparency and better data - constantly monitoring the distance between them with great accuracy. The first satellite moves up and down depending on the amount of mass on Earth below it. The greater the mass beneath it, the more gravity acts upon the satellite, and the further down it moves.

Water is particularly heavy, so depletion of a water-rich aquifer will cause a mass loss that will lessen gravity’s tug on the satellites, allowing them to drift a tiny bit further away from Earth. The small movements of the GRACE satellites are detectable, even if they are only one-tenth the width of a human hair.

Researchers have created an accurate database of groundwater-storage change in water basins by monitoring how much the distance between the satellites changes on a month-to-month basis.

Transparent and accurate data needed

The satellites provide transparency and necessary data that can make up for the lack of on-the-ground monitoring of water resources around the world. For example, the Middle East’s Tigris-Euphrates basin experienced significant drought in 2007, with GRACE satellites detecting decreasing groundwater levels in northern Iraq. Researchers learned that Turkey’s well-developed canal and reservoir infrastructure could store enough water to sustain crop yields during the drought, but Syria and Iraq had no such infrastructure and their farmers were forced to draw on groundwater.

Agricultural yields in Syria and Iraq plummeted after 2007. Turkey – the upstream user– refused to release additional flows to the neighboring countries, and water stress became so severe that some farmers abandoned their lands and migrated to Baghdad. As of this year, the region had the second-fastest rate of groundwater depletion on Earth, after India.

According to Kate Voss, policy fellow at the University of California Center for Hydrologic Modeling (UCCHM), University of California, researchers in Turkey have at times refused to release their water-related data, citing security concerns. The GRACE remote-sensing technology has created a bypass around the reluctance of many countries to release their data.

Charles Iceland, senior associate for WRI’s Aqueduct project, commented:

“Water in trans-boundary river basins must be managed efficiently, equitably, and sustainably. This is not possible without data openness and transparency.”

Using data to build better water management

GRACE and other satellite systems like it have made remarkable progress in spotlighting global water risks. In California, the data and associated research have helped inform a complex federal, state, and local policy discussion since 2010. The next step toward better water management solutions is translating the information into user-friendly online tools - WRI’s Aqueduct team are now working with GRACE researchers with this goal in mind.

Over the next year, WRI will work with the researchers to incorporate the new groundwater data onto Aqueduct’s interactive water maps and global water risk assessment tool.

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