Groundwater use rising sea levels by 0.77 mm per year

Intensive use of groundwater for irrigation and other purposes adversely affected the water cycle, annually raising ocean levels during the second half of the 20th century by about 0.77 millimeters per year, say climate scientists in a paper published in the journal Nature Geoscience.

Sea level depends on the average temperature of the ice cover, the amount of runoff and other climate parameters. All these parameters affect climate change, and therefore the climatologists and oceanographers observe fluctuations in sea level. So, for the last century sea "grew" by 17 inches. A further increase in sea level could cause coastal flooding in Europe and in other parts of the world and can accelerate climate change.

A team led by Yadu Pokhrelya (Yadu Pokhrel) from the University of Tokyo (Japan) to assess how human activity itself — construction and operation of reservoirs, boreholes, irrigation canals and other structures — effect on the growth of sea level.

As the researchers explain, all these forms of human activity have different effects on the water balance of the planet. Thus, the reservoir should reduce the level of the oceans, as they will be trapped and accumulate large amounts of water. On the other hand, the extraction of water from the ground water for industrial and agricultural purposes raises sea level, since most of the water evaporates and ends up in the sea.

Pokhrel and his colleagues evaluated the individual and combined contributions of all types of water management, estimating the total capacity of reservoirs in the last 50 years and the amount of water that is extracted from underground sources of water for various needs.

According to scientists, to date, the reservoir "steals" from the oceans around 10,000 cubic kilometers of water per year. About the same volume of liquid contained in the Lake Superior — the largest and deepest lake in the North American Great Lakes.

On the other hand, the extraction of water from the ground water has a stronger effect on the level of the sea — an annual underground sources replenish the Earth's oceans at 15,000 cubic miles of liquid. This means that the management of water resources adversely affecting the world's oceans each year by adding additional amounts of water in it. A similar pattern can be traced throughout the entire period studied.

According to the calculations of climate scientists, the intensive use of groundwater annually by adding 0.77 mm to global sea level, while the overall level of the ocean rose about 1.8 millimeters.

According to the researchers, this result is complementary findings of the assessment report (AR4), published in 2007 by the Intergovernmental Panel on Climate Change (IPCC), where there was no accurate data on the total water "budget of the oceans. Further research will help to clarify the" share "of humanity and problem of climate change in sea level rise, the scientists conclude.

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