The global decline in groundwater levels

Map of drought is based on satellite data and the results of Grace extended weather observations. Dark red color denotes the effect of drought in Texas this year. The new data analysis indicates Grace satellite to change the level of groundwater in the world. The information provided by NASA and the Centre for Drought Control from the University of Nebraska-Lincoln. (GRACE (born Gravity Recovery And Climate Experiment) — a satellite mission designed to study Earth's gravity field and its temporal?'s Variations associated in particular with the processes of climate change — annotated. Interpreter).

December 23. Throughout the world, there was a decline of groundwater levels in the last 9 years, according to data from two satellites. This tendency is due to the fact that farmers in arid regions too much water is pumped from the ground.

Water disappeared under the southern Argentina, western Australia and some areas of the United States. The decrease is especially evident in California, India, the Middle East and China, that is, where there is a rapidly growing agriculture increases the volume of water consumption.

"Groundwater is being depleted rapidly in virtually all of the major aquifers arid and semi-arid regions of the world," — says Jay Femiglietti — hydrologist at the University of California Center for Hydrologic Modeling in Irvine, whose team showed the new trends December 6 at a meeting of the American Geophysical Union.

Femiglietti and his colleagues find water hidden beneath the surface, using a modern equivalent of the vine (vine in the old days used to search for water — annotated. Interpreter) As two satellites sized vehicle.

The principle of operation of these satellites is as follows: "… they fly to each other on the same orbit a few hundred kilometers above the ground and at a distance of about 220 km apart. These two machines specially named "Tom" and "Jerry" to emphasize that one of them as they are constantly running away, and the second — is catching up '(source: elementy.ru, — Annotated. Interpreter).

Mountains and other large mass education satellites recorded the same in any period, but the movement of water over a long period of time causes the small oscillations of gravity, because of which the change orbits of satellites.

To significantly change the distance between the satellites are needed lots of water flows. Consistently excluding the amount of snowfall, river, lake water and soil moisture, the scientists eventually able to detect changes in the water table to the nearest centimeter in size pieces. Illinois.

In the course of this joint project between NASA and the German Aerospace Center were obtained monthly data on the state of groundwater since 2002. General trends can be identified gaps in monitoring and confirm the existence of problems in those areas where official data on groundwater levels are incomplete or absent.

«Grace is particularly well suited to those regions where there is no way to conduct a meaningful observation," — says Mark Birkens — hydrologist who studies groundwater at Utrecht University in the Netherlands.

For example, as shown China underestimated using groundwater. Unlike the U.S., China lacks a national network for monitoring water. According to Grace annual decline in water level ranged from 6 to 7 cm in the plains, located in the north-east of the country.

In some areas, the culprit may be a change in the climate. For example, the plains of Patagonia in Argentina and south-east of the United States — which was hit hard by drought — water contains less than in 2002

But there is no doubt that one of the reasons for the sharp decline of the water level is the rapid development of agriculture. For example, the agricultural boom in northern India has led to a decrease in the volume of underground reserves of 18 cubic meters. meters per year. That's enough water to fill more than 7 million Olympic swimming pools. And in the central valley of California, which supports one-sixth of the national irrigated land, water reserves were down for a few decades, to the extent that the farmers built new wells and pumping out of which about 4 cubic meters. meters per year.

"People are using groundwater faster than they have time to recover," — says Matthew Rodell, a hydrologist (and member of the project Grace) from NASA's Goddard Space Flight Center in Greenbelt, pieces. Maryland.

Another "hot spot" on the new map Grace is the Middle East, the state of which are of particular concern. The water is pumped out of the Arabian aquifer beneath Saudi Arabia and other countries lying near, was formed thousands of years ago by rain. Once the water disappears be necessary in small showers to fill it.

Climate change will only exacerbate the problem, according Femiglietti. Precipitation become more extreme, drought is only strengthened. The humidity in some areas will be further enhanced, drought, respectively, too, that in the end may accelerate the decline in ground water in the coming years.

Despite the fact that scientists are sounding the alarm, though, but they are still not able to talk about specific amounts. Grace reflects only changes in groundwater, but says nothing about its quantity.

"We really do not know how exhausted the largest aquifers in the world" — says Alex Ritchie of the University of California Center for Hydrologic Modeling.

Some wate layers, such as Nubia, located in the heart of North Africa can be large enough to meet the water needs for centuries. But at the same time there are few reliable estimates of the amount of ground water, preserved in aquifers.

Despite some uncertainty, Leonard Konikou, hydrogeologist from the U.S. Geological Survey in Reston, said that the use of water resources in many areas becomes impossible. Modern irrigation systems, water-saving, could improve the situation, he says. Instead of allowing the precipitation during the rainy season flow into the ocean, you could organize their diversion into aquifers.

"There are many regions in the world, where the water does not have time to resume due to overuse," — said Konikou. "We need to change something."

As a supplement to the article: The Texas drought

Useful for tracking long-term trends in regions with low control data Grace can also contribute in understanding what is happening in the well-monitored areas. For the continental U.S., data were combined with meteorological data Grace will help create a model of the motion of the water layers. The map just shows the simulation results, which reflect the situation as of 28 November. Map shows that the level of water flow decreased by 2 per cent compared with 1948

Translation: Anna Krasnov
Source: ScienceNews.org

 

China sags due to excessive use of groundwater

The inscription on the label: "The area of subsidence of the soil, do not come near."

December 28. Ministry of Land and Resources of China reported that more than 50 cities of 19 provinces in the country is land subsidence. According to experts, this is caused by the overuse of groundwater.

According to statistics of the Ministry, is now all over the country more than two meters of soil slipped on an area of about 79,000 square kilometers. The strongest soil subsidence is observed in the Yangtze River Delta, the North China Plain and the banks of rivers Fenhe and Weihe. In Shanghai, the soil is also, on average, has already slipped by two meters, said the publication "Venhueybao."

According to employees of the ministry of land subsidence caused serious damage and economic losses urban surface and underground structures.

According to the estimates of the Office of Geological Survey of China, a few dozen years, the damage has already reached more than 300 billion yuan ($ 46 billion). The reason for this phenomenon, in the opinion of management professionals is the overuse of groundwater.

Source: The Epoch Times

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