Tuesday, April 17, 2012

Water for All through Desalination and Dams? World Water Crisis 101 (Part 2)

Growing Demand for a Limited Supply of Water

In part 1 of World Water Crisis 101, we explored the problem of water scarcity and water pollution in the face of global population growth. Already, 2.7 billion people are affected by water shortages and, by 2025, and two-thirds of the world’s population could be living under water stressed conditions.

Fact: How the world uses freshwater:
  • about 70 percent for irrigation
  • about 22 percent for industry
  • about 8 percent for domestic use

Water scarcity and polluted water supplies have an enormous impact human health, food production, and economic growth. Solutions to scarcity include moving water from far away, filtering ocean water for drinking, improving agricultural practices and urban water conservation, and safeguarding the available supply by reducing pollution. In part 2 of World Water Crisis, we’ll take a look at desalination and water diversions.

Desalination – Drinking Water from the Sea

Nearly 10 years into record drought conditions in Australia, 5 major cities are turning to ocean desalination to solve their water woes. About half of the world’s current capacity to filter drinkable water from salty ocean water is installed in the middle east, with Israel on track to provide 75 percent of the nations water supply from the sea.

The technology remains controversial, especially in countries with less dire water shortages. Reverse osmosis plants to desalinate seawater are expensive and require enormous amounts of energy to run. Pollution from the energy used by the plants would very likely contribute to global warming, which is expected to exacerbate world water shortages. The resulting brine, super-salty wastewater, has to go somewhere and pumping it back into coastal environments could upset delicate ecosystem balances.

Dams and Aqueducts – Drinking Water from Far Away

Freshwater is not evenly distributed around the world. Even relatively water rich nations may have regional scarcity problems and many cities have grown up in places with inadequate water to support their modern populations.

Fact: In 60 percent of European cities with more than 100,000 people, groundwater is being used at a faster rate than it can be replenished.

Many proposed solutions to water scarcity assumes that water is portable. Nations have long dammed rivers to create reservoirs of water for cities and farms. Dams have been controversial and damaging to the local ecosystems.

Simple dams and reservoirs are nothing compared to the kinds of projects being proposed to meet growing urban water demands around the world. It has long been a fear of the U.S. Great Lakes states that population growth in the Southwest will lead to grand projects to divert water from the lakes or upper Mississippi River to supply Phoenix, Tempe, and Albuquerque.

Before you dismiss the fear as ridiculous, remember that the Colorado River was diverted to supply Los Angeles more than a century ago. The state of Nevada recently approved a series of pipelines and pumping stations to move groundwater hundreds of miles from the east to the city of Las Vegas.  And China is undertaking a project that the New York Times is comparing with diverting the Mississippi to supply Boston, Massachusetts.

China to Build the World’s Largest Water Diversion Project

China began construction on a canal and aqueduct project in 2002 that will ultimately divert 6 trillion gallons of water every year from the southern Yangztee River to supply the arid plains in the north.

“Since 2002, China has spent 138 billion yuan ($22 billion) on the project and expects to spend another 64 billion yuan ($10 billion) this year alone. The government has also relocated 330,000 people who lived near a reservoir on one of the routes.” – The New York Times

Massive Water Diversions Come with Big Costs

Such enormous engineering projects may sound appealing, but moving water – both heavy and bulky – over great distances takes a tremendous amount of energy.  For example, California spends nearly 20 percent of its electricity use to moving water around.
On the environmental impacts of such schemes, Brian Richter of The Nature Conservancy and University of Virginia writes:

“We should be careful about ‘robbing Peter to pay Paul.’ As we dry up a river or lake to harvest or export its water, the health of fish populations and natural freshwater ecosystems plummet.  In virtually all of the large rivers that have begun to go dry, fisheries have been decimated, leading to severe hardship for local people that depend upon that food source for their subsistence and livelihoods.  Last year, I published a journal paper with colleagues at The Nature Conservancy that suggested that depletion of a freshwater source by more than 20% will likely have harmful ecological and social consequences.”


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