Srinagar, Oct 4: A fresh sinkhole reported in the Brengi Nalla catchment in Kokernag has renewed concern over ground stability in the limestone-rich terrain of the Brengi, a key Jhelum tributary.
The opening was reported at Gohihard on Sep. 27, about 1.5 kilometres downstream from the Wandevalgam collapse of 11 February 2022. Officials diverted the Brengi flow and filled the cavity with sand and gravel, after which the stream resumed flowing smoothly.
The Brengi has recorded sinkhole activity in 1995 and 2022. The latest opening is the first reported in the catchment since the major Wandevalgam collapse.
The 2022 event prompted a detailed investigation led by hydrogeologist Riyaz Ahmad Mir and co-authors, published in Environment, Development and Sustainability by Springer Nature in 2023. Researchers classified the Wandevalgam feature as a “Collapse Sinkhole.”
They attributed the collapse to the failure of an underground cavern roof in fractured Triassic limestone after “prolonged dissolution and physical erosion by the weakly acidic stream and groundwater circulation.” The limestone contains “large structural discontinuities (bedding planes, fractures, joints and shear zones) and karst features.”
About 80 cubic metres of water had accumulated before the collapse, while geophysical surveys indicated caverns extending about 100 metres downstream.
The sinkhole swallowed the entire Brengi flow, with an estimated 15.03 cubic metres of water per second disappearing underground for several weeks, drying up more than 20 kilometres of the downstream channel.
The loss affected aquatic life and disrupted domestic water supplies, irrigation, agriculture and horticulture.
Tracer tests showed that the missing water travelled 16 kilometres underground to Achabal Springs at an average speed of about 1.3 kilometres per hour.
A separate NIT Srinagar investigation found that about 90% of the captured water had an outlet at Achabal.
Twenty-nine days after the Feb. 11, 2022, collapse, on March 12, the springs at the Achabal Botanical Garden suddenly surged.
In a subsequent diversion test, NIT researchers recorded a rise in spring discharge about five hours after Brengi water was diverted into the sinkhole, followed by a decline after the diversion stopped.
The investigation also identified five smaller sinkholes upstream and downstream of the main collapse.
Their “near-linear pattern” pointed to a wider network of underground cavities and drainage channels.
The study mapped 77.15 square kilometres downstream as a high-risk area, including about 58% agricultural and horticultural land, 25% vegetation cover and 10% built-up area.
Researchers described the Wandevalgam and Gohihard sinkhole as a “part and characteristic feature of karst topography of the area” and warned that “there can be several sinkholes in the area, but only become evident once they collapse fully.”
They called for “a detailed study on sinkhole susceptibility and hazard assessment,” along with long-term monitoring and improved management of local groundwater resources and karst springs.
The latest Gohihard cavity was considerably smaller than the 2022 opening. No significant discharge was observed before it was filled.
No scientific assessment has so far linked the 2026 opening to the cavern or the 16-kilometre underground route documented after the Wandevalgam collapse.
However, the new opening adds another episode to the Brengi’s sinkhole history, while the earlier investigation shows that a substantial part of the catchment’s drainage system lies beneath the surface.
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