The US Geological Survey has released a report highlighting the alarming rate of groundwater depletion in the United States.
The report says that between 1900 and 2008, the US lost 1,000 cubic kilometers of water from its 40 major aquifers – that’s an average rate of 9.2 cubic kilometres a year. Even more alarming is the increasing rate of loss – between 2000 and 2008, it had jumped to an average of 25 cubic kilometres a year.
Much of the water pumped from aquifers ends up running into the sea. The US Geological Surrvey estimates that US groundwater depletion between 2000 and 2008 accounted for 2% of the sea level rise in that period.
The situation in the United States is by no means the worst.
- India has 20% of the Earth’s population, but only 4% of its water. Water tables are dropping fast in some of India’s main agricultural areas. There are 35 cities with populations of more than a million in India. None of these cities is able to distribute water to its population for more than a few hours a day – the average duration of supply being 3.3 hours a day.
- Hebei Province, which surrounds Beijing, is one of China’s major wheat and corn growing provinces. Water tables there have been falling rapidly and 969 of the 1,052 lakes have dried up. Because of the shortage of water, steel mills around Beijing have been ordered to stop expanding and move to the coast where they can use desalinated sea water for cooling.
- When Bashar al-Assad became President of Syria in 2000, he opened up the regulated agricultural sector to big farmers, allowing them to buy up land and drill as much water as they wanted. As a result, the water table was severely diminished. When drought struck between 2006 and 2011, the water table was too low to carry the country’s farmers though. Some 800,000 farmers and herders lost their livelihoods.
- Saudi Arabia had been self-sufficient in food production based on “fossil water” from ancient aquifers that are being recharged very slowly, if at all. This water supply started to decline in the early 1990s and now Saudi Arabia is importing all of its food. Saudi Arabia is now desalinating water and pumping it 300 kilometres inland to its capital city, Riyadh.
Desalination is seen as a backstop water source but it involves high capital costs, high energy consumption, high transportation costs and environmental issues in the disposal of the resulting brine. One approach to overcome some of these difficulties is the “saltwater greenhouse” in which seawater is desalinated by evaporation and condensation inside a greenhouse using solar energy as the only energy supply.