Mississippi River Delta to “Drown” by 2100?

By Rebecca Carroll, for National Geographic News

The Mississippi River Delta is drowning, according to new research that predicts the surrounding coastline will be inevitably reshaped in coming decades.

“There’s just not enough sediment to sustain the delta plain,” said study author Michael Blum of Louisiana State University in Baton Rouge.

Deltas are coastal landmasses created from a river’s sediment deposits as the water flows out to sea. The Mississippi River’s delta plain, for example, includes the lacy “toe” of southern Louisiana. (See a Louisiana map.) All deltas are degrading to some extent, as their sediment settles and sinks. But a delta can sustain itself or even grow if its parent river regularly deposits enough new material.

Today sediments collected along the Mississippi cover about 23,360 square miles (60,500 square kilometers) ranging in thickness from less than 33 feet (10 meters) upstream near Memphis, Tennessee, to about 328 feet (100 meters) in the delta at the tip of southern Louisiana.

The drainage basin of the roughly 2,350-mile-long (3,782-kilometer-long) river, however, includes about 40,000 dams and levees built over the past century.

These structures control flooding and improve navigation, but they also trap sediment or funnel it completely through to the sea.

Previous studies suggested that dams and reservoirs built since 1950 have trapped as much as 70 percent of the river’s natural amount of sediment. With less material feeding it, the delta plain has been experiencing erosion.

But even without the dams and levees, the amount of sediment flowing downriver would no longer be enough to sustain the delta because of rising seas, the study authors say.

Tough Choices

The researchers base their conclusions on estimated delta levels over the past 12,000 years, which show significant changes more than 7,000 years ago, when meltwater from the last ice age quickly filled the oceans.

The Mississippi Delta plain retreated inland at that point, and it was only after sea level rise had slowed considerably that the delta again grew seaward. Current sea level rise, however, may be three times faster than it was the last time the delta was able to grow.

The team therefore estimates that as much as 5,200 square miles (13,500 square kilometers) of delta land could disappear by 2100—an area only slightly smaller than Connecticut.

For now the study authors don’t have a solution, and they add that plans to save the delta plain—such as redirecting and possibly adding sediment—will almost certainly involve sacrifices.

“They can [divert sediment to areas] downstream from, say, New Orleans, but that means that areas [of the delta plain] farther upstream will be submerged,” Blum said.

“Tough choices have to be made, and they need to be made fast.”

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Source: National Geographic News

Climate forecasts crucial to water resources and poverty reduction – UN agency

The chief of the United Nations meteorological agency today called for weather forecasts to play a greater role in planning for economic development and poverty reduction because of the impact climate change has on water resources.

Michel Jarraud, the Secretary-General of the World Meteorological Organization (WMO), told the World Water Congress that the agricultural, energy, tourism and health sectors are among those most affected by the impact of climate change due to drought, deterioration in water quality, increased run-off and an increase in the salinization of ground water as a result of rising sea levels.

“Mainstreaming climate change in decision-making processes will therefore be central to all development and poverty alleviation efforts,” he said at the meeting, held in Montpellier, France.

Mr. Jarraud reminded attendees of the summit that six of the eight Millennium Development Goals (MDGs) relate to water resource management, and that severe flooding, drought and cyclones caused by climate change seriously obstruct efforts to meet the MDGs by 2015.

WMO has launched an appeal for funding to set up hydrological information systems that can provide timely, accurate and comprehensive water resources information and support economic development through better land and water resource strategy planning.

The growing demand for a diminishing water supply is among the challenges to resource management. One sixth of the world’s population, mostly in rural areas, on small islands, regions dependant on water from glaciers and snow melt, is adversely affected by the shortage of ground water.

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Source: UN News Centre

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Global warming could affect water supplies in North: researcher

A changing climate may someday shrink water supplies in Arctic communities, said a researcher at a climate symposium in Iqaluit.

Less snow in the winter and less rain in the summer, combined with warmer temperatures and higher winds that increase evaporation rates, raise concerns about the future of water supplies in the already semi-arid Arctic, said Paul Budkewitsch of Natural Resources Canada.

“And [it] at least raises the question, ‘Well, are we going to have enough water?’ The answer is probably yes,” Budkewitsch said Wednesday, on the last day of a symposium in the Nunavut capital on adapting to climate change.

“But the question is, how long is that answer going to be yes? Is it many, many years into the future, or is it a few years into the future?”

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Source: CBC Canada

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Global warming aside, fresh water dwindling

According to a study published in the July 14, 2000, issue of Science, one-third of the world’s population is water-stressed, with 8 percent classified as severely water-stressed, including the western United States and northern Mexico, South America, India, China, Africa surrounding the Sahara Desert, and southern Africa and Australia.

“Water stress” has profoundly different meanings in developed and developing countries. In Africa and many parts of Asia, it means inadequate water for drinking, sanitation and crops. In emerging economies such as India and China, it translates as an inability to meet the dietary and lifestyle aspirations of a growing middle class.

Water stress in richer nations, and in places such as Phoenix and Las Vegas, means an inability to sustain a growth economy and support lavish oasis-style lifestyles featuring irrigated lawns, outdoor swimming pools, artificial waterfalls and urban lakes.

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Source: The Arizona Republic

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