Granada, south-eastern Spain
Some areas of Spain’s Andalusia region may inspire that familiar sinking feeling – and it’s not imagined; sustained drought and relentless heat is making the soil in the region subside, potentially causing structural issues in south-eastern Spain.
Over half a century of ground exploration, research scientists have analysed data from three separate satellites and have confirmed that the land is sinking at the rate of a centimetre a year in periods of drought. Simultaneously, the researchers have also kept a close eye on groundwater extraction in the Vega de Granada – the subterranean aquifer that lies beneath the Granada basin – and have found that extraction could be matched to the land sinking in some parts of the river basin.
Various cracks in the pavements and streets of more than one municipality can be traced to a period of sustained drought that took place between 2003 and 2009. However, between 2011 and 2014, Granada’s rainiest period, no evidence of soil subsidence could be found.
The research study, published in the Journal of Hydrology, was jointly led by José Miguel Azañón from the University of Granada and Rosa Maria Mateos from the Spanish Geological Survey.
While the authors have said that the data is “not alarming”, they have also stated that “these data are of enormous interest for an adequate management of the aquifer, especially during periods of drought, such as the one we are currently experiencing.”
However, they have also implied that sustained drought could bring about hazardous problems.
In a world where heat waves and drought could become normative in the southern parts of Europe, researchers have warned that in the long-term, temperatures that have the potential to rise dangerously high could bring the Sahara Desert down to the Mediterranean.
Thus, the response of water-bearing rocks and clay – called the phreatic level by hydrologists – to flood or drought is of particular interest to local authorities all the way to the insurance industry. After all, if everything sinks at a uniform rate, nothing will be amiss, but if subsidence occurs in some streets and areas, but not others, cracks and infrastructure woes would begin to appear.
“In very vulnerable areas, with high content of clays, decreases of just a couple of metres in the phreatic level could cause subsidence,” the authors continued. “An accumulation of displacements could lead to a subsidence of several centimetres per decade, which would present a long-term danger for the villages located in the Vega de Granada area.”
Source: Climate News Network