Overexploitation of groundwater, coupled with virtually no recharge of the water table in the absence of good rains in the last six years, appears to have triggered the geological event known as “sinkhole”, the second such in this perennially drought-prone district of Andhra Pradesh.
A sinkhole had first formed in the last week of January 2015 on the Chitravati river bed near the Goddumarri village of the Yellanur mandal of the Anantapur district.
Close to it was noticed another sinkhole on Sunday after villagers heard a deafening sound from the Chitravati riverside at around 10 AM.
While the first sinkhole had a depth of 30 feet and a width of 25 feet, the latest one is smaller with a depth of around 20 feet and width of 15 feet.
Sinkholes usually form in soils characterised by rocks of gypsum or dolomite or limestone which melt in water available in the sub surface channels leading to a sudden collapse, said Manikanta, senior geologist.
In the case of the Chitravati riverbed too, the cavity was triggered by depletion of groundwater, say officials.
Deputy Director of Groundwater Department P. Purushottam Reddy confirmed the development and said the intensity of drawing groundwater through a string of agriculture borewells was high in the vicinity of the river, where there were a number of sweet lime orchards.
Lack of good rains in the last seven years only added to the problem.
“Limestone occurs at a depth of 250 ft below the surface in the Chitravati river belt which is where the water table also starts. With the water depleting to around 750 to 850 ft, the cavernous limestone zone develops into a layer collapsing into itself,” Mr. Reddy explained.
