The Zangmu Dam, located on the Yarlung Tsangpo River (which becomes the Brahmaputra in India), is one of the closest and most significant Chinese hydropower projects with indirect but serious implications for the Rasuwagadhi–Bhote Koshi river system.
While Zangmu is not on the Bhote Koshi itself (which flows from Tibet’s Kyirong County into Nepal at Rasuwagadhi), it’s a major upstream flow regulator within the greater Himalayan watershed. Here’s how it might contribute to hydrological disruption affecting regions like Rasuwagadhi:
1. Flow Regulation and Sudden Release
Zangmu, as a run-of-river dam, stores and releases large volumes of water daily for electricity generation. This artificial manipulation can:
- Alter the natural timing of flows, weakening the ecosystem’s ability to stabilize slopes and absorb excess meltwater.
- Lead to downstream surges that compound monsoon flooding or glacial lake outburst floods (GLOFs).
Though the Bhote Koshi is a tributary of the Koshi River, the overall pressure on Himalayan drainage systems from projects like Zangmu increases the risk of cascading failures—as local tributaries get overwhelmed by a combination of natural and controlled releases.
2. Glacier Melting and Permafrost Destabilization
Hydropower infrastructure requires road construction, deforestation, and drilling—all of which:
- Expose permafrost layers to accelerated melting.
- Disturb the delicate glacial balance that keeps supraglacial lakes intact.
This is precisely what occurred in Kyirong County, where a permafrost collapse triggered the GLOF on July 8.
3. Data Secrecy and Lack of Transparency
China does not share real-time dam discharge or reservoir data with Nepal, India, or Bhutan, creating a dangerous information vacuum during disasters.
- Nepal had no prior warning before the July 8 flood, though satellite data later confirmed rapid drainage from a glacial lake in Tibet.
- If China had real-time water monitoring systems tied to its dams and shared data regionally, early warning systems downstream could have been activated.
Conclusion: A Regional Domino Effect
While the Zangmu Dam is not on the same river as Rasuwagadhi, it plays a role in the broader hydrological degradation of the Himalayas:
- It destabilizes upstream glacial zones through temperature, seismic, and ecological interference.
- It obstructs natural flow dynamics, increasing sedimentation and flood risks downstream.
- It amplifies the impact of GLOFs when such disasters coincide with high-volume dam releases or rainfall events.
