For Much of the World, Demand For Water Outstrips Supply

ananyo writes "Almost one-quarter of the world's population lives in regions where groundwater is being used up faster than it can be replenished, concludes a comprehensive global analysis of groundwater depletion (abstract). Across the world, human civilizations depend largely on tapping vast reservoirs of water that have been stored for up to thousands of years in sand, clay and rock deep underground. These massive aquifers — which in some cases stretch across multiple states and country borders — provide water for drinking and crop irrigation, as well as to support ecosystems such as forests and fisheries. Yet in most of the world's major agricultural regions, including the Central Valley in California, the Nile delta region of Egypt, and the Upper Ganges in India and Pakistan, demand exceeds these reservoirs' capacity for renewal."

Comments

When you unbalance a stable system, it falls over

[Tastecicles]

Physics 101.

When you pump water out of the ground, it leaves a void. When you don't backfill, the void eventually collapses. The oil industry is aware of this problem (that and oil doesn't tend to want to just lift itself out of the ground once the initial pressure does its thing), which is why they use seawater to displace the oil: seawater is pumped in, oil flows out or is pumped out leaving the void which is then backfilled under gravity through a strategically placed hole or two.

Back to the topic: the stable system of rain=>aquifer is disrupted to greater or lesser degrees by human activity. That's obvious. The amount of rain remains constant (more or less), which means the amount of water removed from the aquifer is gone. Simple as. The global water industry has a few options to try and deal with this problem before we start seeing entire cities disappearing into sinkholes:

1. Backfilling. Something not currently done, but it begs the question as to what to backfill with?
2. Alternative sources. We have viable desalination technology (geothermal, solar stills, seat salt extraction plants(!))... we have made great strides in atmospheric water extraction to the point where a plant in the middle of a desert can turn sand into golf course. One option that I don't think has been properly explored is a wide area water grid, possibly national or international in scale. We have the technology, we have the capability, the chock under that wheel is politics.

Just as important

[Grayhand]

We're also polluting ground water at an alarming rate. With more droughts likely ground water is critical to agriculture in the US as well as drinking water. I used to live in LA and a disturbing number of wells were contaminated some even with radioactive waste, none from power plants it was industrial pollution. I'm in Phoenix now and the city is sinking due to the aquifer collapsing as the water is drained. That's capacity that is perminately lost. For every foot of settling that's the city a foot deep in water that's lost. The city has lost 74.5 million acre-feet in the last 70 years to give an idea what Phoenix is facing.

Re:speaking of which

[Spy Handler]

there is no water shortage, there's only energy shortage. There's water everywhere for the taking. With cheap enough energy, you can get all the freshwater you need from distilling seawater or towing icebergs from the Arctic or reverse osmosis or any of a thousand different ways.

Re:When you unbalance a stable system, it falls ov

[Tastecicles]

You're adding a step where there doesn't need to be one: solar stills are basically greenhouses with pools in. The condensate runs off into side channels for utilisation, the salts and effluent are left in the pool to be scraped and disposed of.