In the remote Himalayan district of Lunana, a high-stakes operation is underway to protect communities from the looming threat of a glacial lake outburst flood (GLOF). Thorthormi Lake, already swollen from past flood events in 2019 and 2023, poses an urgent risk to thousands living downstream.
The National Centre for Hydrology and Meteorology (NCHM), backed by the World Bank, has launched a pilot project to lower the lake’s water level using a gravity-powered siphon system — a first for Bhutan’s treacherous glacial terrain. The method relies on siphon pipes to gradually drain excess water, reducing pressure on the fragile moraine dam that separates Thorthormi from the adjacent Rapstreng Lake. Experts warn that if this natural barrier collapses, the resulting flood could be catastrophic.
This initiative is more than an engineering challenge — it’s a test case. If the siphon proves effective, it could offer a sustainable, low-cost solution for mitigating similar threats in the region, potentially sparing villages from repeated evacuations and loss.
The people of Lunana are central to the mission’s success. Residents are assisting with on-site logistics and monitoring, while newly appointed hydromet technician Nedup Dorji gathers vital data to strengthen Bhutan’s early warning systems. His work, combined with the siphon operation, could buy precious time in the event of rising flood risk.
For now, all eyes are on Thorthormi Lake — and whether this pioneering effort can hold back the waters of disaster.
