Source: JPL | News | Study: Third of Big Groundwater Basins in Distress About one third of Earth's largest groundwater basins are being rapidly depleted by human consumption, despite having little accurate data about how much water remains in them, according to two new studies led by the University of California, Irvine (UCI), using data from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites. This means that significant segments of Earth's population are consuming groundwater quickly without knowing when it might run out, the researchers conclude. The findings are published today in Water Resources Research. "Available physical and chemical measurements are simply insufficient," said UCI professor and principal investigator Jay Famiglietti, who is also the senior water scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. "Given how quickly we are consuming the world's groundwater reserves, we need a coordinated global effort to determine how much is left." . . . I heard a synopsis on the Rachel Maddow podcast. Bob Wilson
My expectations: solar-wind, hydrogen protons - combine with atmospheric oxygen to make water meteors - may carry small amounts of water some amount of H{2}O broken apart by solar flux and H{2} escapes Bob Wilson
Increasing numbers of humans on the earth contain the water in their bodies. Average water carried is 40 liters per person.
On an geological timescale, no. Infalling cometary debris adds water, though the rate remains poorly known. 'Evaporation' off the top of the atmosphere (mostly hydrogen atoms from broken-up water molecules) slowly takes water away, in a process strongly dependent on sunlight and the planet's gravity. The much shallower gravity well of Mars allowed most of its water to escape long ago.
Fuzzy1, the whole idea of comets 'watering' earth during Late Heavy Bombardment looks strong to me. Since then, fewer Oort or Kuiper objects have entered the inner solar system. I want to say that the earth's surficial water pool has been ~constant for 3 billion years, but this is not certain. Mars may have never done tectonics (the way for upper mantle to release volatiles), or it may done, but shut down long ago because of smallness. What happens on Venus is 'behind the veil'. Orbiters look down at a ridiculously thick atmosphere, and landers promptly melt. All we know, really, is that because of prior circumstances, this here planet turned out to be quite bio-friendly
