17 November, ABC Science, New map of Earth’s groundwater to help estimate when it may run out. Less than 6 per cent of ground water in the upper two kilometres of the Earth’s landmass is renewable within a human lifetime, according to a new map showing the world’s hidden groundwater. “This has never been known before,” said the study’s lead author, Dr Tom Gleeson of the University of Victoria in Canada. “We already know that water levels in lots of aquifers are dropping. We’re using our groundwater resources too fast -faster than they’re being renewed.” Using data and computer models, an international group of hydrologists has produced the first data-driven estimate of the Earth’s total supply of groundwater. “Since we now know how much groundwater is being depleted and how much there is, we will be able to estimate how long until we run out.” The study, published in the journal Nature Geoscience, estimated a total volume of underground water to be almost 23 million cubic kilometres, of which 0.35 million cubic kilometres is younger than 50 years old. Underground water is found beneath the Earth’s surface and is recharged by rain, snow or water that leaks from the bottom of lakes and rivers. Its age can be a few months to millions of years. It can be found as deep as nine kilometres, according to the United States Geological Survey. “Since we now know how much groundwater is being depleted and how much there is, we will be able to estimate how long until we run out,” Dr Gleeson said. Read More here
13 November 2015, Climate News Network, Global warming drains the water of life. Melting snowpack in Turkey’s Lesser Caucasus mountains. New research warns that rising temperatures are reducing the mountain snow on which billions of people in lowland areas depend for their water supply. Up to two billion people who depend on winter snow to deliver their summer water could see shortages by 2060 as upland and mountain snowpacks continue to dwindle. An estimated 300 million people could find, 45 years on, that they simply won’t have enough water for all their needs, according to new research. Climate change driven by rising atmospheric levels of carbon dioxide – in turn, fed by human combustion of fossil fuels – may already be affecting global precipitation. Researchers have consistently found that much of the world’s drylands will increase as global average temperatures rise. But warmer temperatures increasingly also mean the water that once fell as snow, to be preserved until the summer, now falls as winter rain, and runs off directly. The snow that does fall is settling at ever higher altitudes and melting ever earlier. Reliable flow This is bad news for agricultural communities that depend on a reliable flow of meltwater every summer. California is already in the grip of a sustained drought, made worse by lower falls of snow. Great tracts of Asia depend on summer meltwater from the Himalayan massif and the Tibetan plateau. Justin Mankin, an environmental scientist at Columbia University’s Earth Institute in the US, and colleagues report in Environmental Research Letters journal that they studied 421 drainage basins across the northern hemisphere. Read More here