Changes in global surface water over the past 32 years since 1984 have been quantified at 30-metre resolution from satellite imagery. Three million freely available Landsat satellite images have been used to record the months and years when water was present, where occurrence changed and what form changes took in terms of seasonality and persistence. This globally consistent, validated data set shows that impacts of climate change and climate oscillations on surface water occurrence can be measured and that evidence can be gathered to show how surface water is altered by human activities.
The data reveals that between 1984 and 2015 permanent surface water has disappeared from an area of almost 90,000 square kilometres, roughly equivalent to the area of Lake Superior. Over 70 per cent of global net permanent water loss occurred in the Middle East and Central Asia, linked to drought and human actions including river diversion or damming and unregulated withdrawal. Losses in Australia and the USA linked to long-term droughts are also evident.
New permanent bodies of surface water covering 184,000 square kilometres have formed. Almost all continental regions show a net increase in permanent water. Much of the increase is from reservoir filling, although climate change has also contributed. High-resolution mapping of global surface water and its long-term changes, Jean-François Pekel, Andrew Cottam, Noel Gorelick & Alan S. Belward, Nature 540, 418–422 (15 December 2016) doi:10.1038/nature20584