Facts fuzzy, fingers crossed, HP waits for flood from Tibet

Also, the Chinese team had to stop short because of ‘‘fresh landslides.’’ The lake has formed at a remote location where there are no communication links. The Indian government is not insisting on the Indian team going there because it is unlikely that they will make it to the actual site.

The lake was formed late last month as a result of heavy landslide when debris blocked Pareechu river forming a lake. Pareechu is a tributary of Spiti that meets Sutlej.

One result of the Chinese visit is that the dimensions of the lake are clearer: it’s estimated to be spread across 188 hectares, the wall infront is 35 metres high. The width is 1.5 km and the length 6 km. No accurate measure of the depth has been ascertained yet.

Experts have calculated that if the wall gives way, the flood would be almost double the intensity of what it was in 2000 when it killed nearly 100 people and caused damage worth Rs 200 crore on bridges and roads. At that point, the flow at Rampur, nine kilometres from Nathpa Jhakri was 5000 cusecs.

The Nathpa Jhakri plant, the first check in the line of water, does not have a large reservoir. Y N Apparao, CMD of Sutlej Jal Vikas Nigam Limited (SJVNL), said that all five sluice gates of the Nathpa Jhakri reservoir were opened and water in the reservoir emptied up to the lowest possible limit. The five sluice gates have a discharge capacity of only 6,500 cusecs.

In the 2000 floods, since there was no warning, flood waters had entered the powerhouse of the Nathpa Jhakri hydel power project.

The walls giving in is inevitable, sources said, because the size of the lake is increasing. Though there is some leakage, it implies that the pressure on the debris wall is building up. The biggest indication of the build-up is that the flow in Sutlej that is being closely monitored has not gone up.

This episode has once again brought into sharp focus the need to share data on common rivers between India and China. After the 2000 floods—caused as a result of a similar phenomenon—China had agreed to provide flood warning. However, there is no permanent monitoring station on the Sutlej on the China side.

According to sources, India has also offered to pay for the setting up of a station considering the damage it causes to Himachal in the event of a landslide anywhere on the river in the upper reaches. So far, the requests have gone unheeded. For the last few years, there are three monitoring stations on the Brahmaputra that provide regular data on water level, rainfall and discharge. A similar system is required for Sutlej, said an official from the Ministry of Water Resources.