15/06/2026
🏗️ Construction Update | UMHEP 46.25 MW Hydropower Project, Myagdi
Underground Desander : A Critical Component in the Making
One of the key civil structures currently under construction at the Upper Myagdi Hydropower Project is the Underground Desander, a vital facility designed to protect the project’s electromechanical components and ensure long-term operational efficiency.
What is an Underground Desander?
An underground desander is a sedimentation chamber excavated within rock, typically located between the headworks and the headrace tunnel. Its primary function is to trap and remove suspended sediment particles particularly fine sand and silt from the diverted river water before it enters the waterway system and ultimately reaches the turbines.
Why is it critical?
The Myagdi River, like most Himalayan rivers, carries a high sediment load, especially during monsoon season. Without effective desanding, these abrasive particles would:
• Cause severe erosion and wear on turbine runners, guide vanes, and other hydraulic components
• Significantly reduce the operational lifespan of expensive electromechanical equipment
• Lead to increased maintenance costs and unplanned downtime
How it works:
Water flows into the desander basin at a controlled, reduced velocity. As the flow slows, gravity causes sediment particles to settle to the bottom of the chamber. The clarified water then continues through the headrace tunnel toward the powerhouse, while the settled sediment is periodically flushed out through flushing conduits back to the river downstream.
At UMHEP:
The underground desander at our project site is being constructed deep within the rock mass, offering natural protection from surface conditions and minimizing the project’s environmental footprint on the surface. The excavation, concrete lining, and hydraulic design of this structure reflect our commitment to engineering excellence and sustainability.
