Over the last nine years, the level of underground water has decreased in many parts of the world, read as satellite data.
Water activity disappears from the southern and western Australia, California, China, India, the Middle East, where agriculture is actively developing and requires more moisture. In other words, the soil and ground water are not going through the best of times in almost all major aquifers in arid and semi-arid areas.
Jay Familetti University of California, Irvine (USA) and his colleagues came to this disappointing conclusion on the basis of a pair of US-German satellite GRACE (Gravity Recovery and Climate Experiment, «Climate Experiment and gravitational perturbations"), who spend their measurements 2002.
Scientists have dubbed the satellites "Tom" and "Jerry," because they fly one after another, like a cat for mouse. Changes in Earth's gravity in the areas over which they pass, forcing vehicles to approach it, then move away. Mountains and other large mass concentration have a strong and continuous exposure, and the water is in constant motion, creating a subtle fluctuations.
By laborious extraction from the data about the snow, rivers, lakes, and soil moisture, researchers were able to obtain information on literally centimeter changes in the water table.
The result is often contradicted by ground observations. For example, China was found to underestimate the flow of groundwater. Under the north-eastern plains of China falls to the level of 6-7 cm per year.
In some areas, groundwater is not leaving because of agriculture, as a result of climate change. This applies to Patagonia (Argentina) and the southeast United States, which was struck by a great drought.
Still, the responsibility for the strongest decline of the water table is assigned to agriculture. The agricultural boom in northern India has led to the fact that there is groundwater annually lose about 18 km ². In the Central Valley of California, which accounts for one-sixth of U.S. irrigated land, landowners are pumping almost 4 km? year.
Another "hot spot" — the Middle East. Thousands of years ago, when the climate there was quite different, the rain filled the aquifer. The current draft can no longer compensate for the fact that people are pumping.
The situation is complicated by the uncertainty. No study has not yet been able to give a credible estimate of world reserves of groundwater.
The results were presented at the American Geophysical Union.
Prepared according ScienceNews.