Measuring change

November 10, 2015

Curtin scientists used the GRACE satellites to measure data on water usage in the Nile Basin from 2002 to 2011.

Using a combination of satellite data and ground observations, spatial scientists are able to measure water use, land changes and climate variability with greater accuracy than ever before. Professor of Geodesy Will Featherstone at Curtin is measuring the rate at which land in Perth is sinking due to water drawn from the city’s underground aquifers.

“As the water gets pulled out, the weight of the rocks on top causes the land to subside,” he says. “We’re using satellite techniques, GPS, plus a radar technique called InSAR, where we take a radar picture of Perth every 11 days. We stack all these images together to deduce the subsidence.”

The study is also being used to correct records of sea level rise in Perth, which have been exaggerated in some places because of the sinking land. The team is also working further afield, using precision satellite measurement techniques to stave off conflict over water distribution in Northeast Africa.

Using data from the Gravity Recovery and Climate Experiment (GRACE) satellites, spatial scientist Associate Professor Joseph Awange has been able to show that between 2002 and 2011, Egypt over-extracted water from the Nile Basin for irrigation purposes.

The satellite data also showed a sharp drop in rainfall across the region in November and December 2010 and a decline in rainfall over the 10-year study period in the Ethopian Highlands.

Awange says measuring water use in the Nile Basin can determine if countries are abiding by the 1929 Nile Water Agreement to share the world’s longest river.

Analysing satellite data could show which countries are over-extracting water from the Nile. “If the upstream countries use a lot of the water, then the chance is that the downstream countries such as Egypt will not have enough to sustain them,” says Awange.

“Egypt has threatened several times that they’re ready to go to war if the upstream countries extract more than is necessary,” he says.

Michelle Wheeler

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