Glacier Lake Outburst Flood (GLOF) early warning (GLOF EWS) is a service extended to the public by the Department of Hydro-met Services (DHMS), Ministry of Economic Affairs as a part of its civil contingencies to help prepare, respond and recover from GLOF events. Its objective is to provide adequate, reliable and timely GLOF warnings downstream to safeguard life and property downstream.

The GLOF EWS system is directly look after by the Hydrology Division, Department of Hydro-met Services, MoEA.

On October 7, 1994, a Glacial Lake Outburst Flood (GLOF) occurred on Lake Luggy in Lunana, sending a flood wave down the Phochhu and Punatsangchhu that claimed 22 human lives and caused massive property damages and loss of livestock and agriculture land. Although major flooding had occurred in the past, the 1994 GLOF was the catalyst for the need to establish an early warning system (EWS) giving downstream inhabitants time to evacuate.

The first automatic GLOF Early Warning System was installed in the Punakha-Wangdue Valley through the financial support from LDCF through GEF/UNDP under the project Reducing Climate Change-Induced Risks and Vulnerabilities from Glacier Lake Outburst Flood in the Punakha-Wangdu and Chamkhar Valleys with co-financing from the Punatsangchhu Hydropower Project Authority (PHPA-I and PHPA-II) and Austria Development Cooperation. The system was operational since September 2011.

Profile of GLOF Early Warning System in Punakha-Wangde Valley
A GLOF EWS installed in the Punakha-Wangdue is composed of 6 remote Automatic Water Level Monitoring Stations and Automatic Weather Stations (AWS) and 17 Sirens to warn vulnerable communities along the river valley downstream. Iridium satellite communication is used to transmit data from remote stations to control room for operation and monitoring of GLOF in real time and as well as activation of sirens to issue warnings in the event of GLOF. Control station operators can view the latest data from any of the 23 stations using custom developed software by Sutron.

The Department of Hydro-met Services have plans to expand the GLOF Early Warning system network to other basins in Bhutan. GLOF Early warning system on Mangdechhu and Chamkharchhu river basins will be installed with the support from JICA Technical Cooperation Project (TCP) during the 11th FYP.

The schematic diagram of the present GLOF EWS in Punakha-Wangdue Valley is shown in the Figure 1.