CHANDIGARH, Aug 12: A lake in Tibet is only half as deep as initially calculated but fears it could burst its banks and flood a Himalayan valley across the border in India remain, an Indian official said on Thursday.

The information came a day after Beijing urged New Delhi to make preparations for "disaster prevention" in the region as there still was a possibility of the lake breaking its dykes or overflowing "any time".

"Recalculations based on data available from Indian satellites and the latest information received from China show the depth of the lake is 35 metres as against the earlier estimated 70 metres." said H.K. Sharma, director of an Indian power project downstream from the lake.

"The possibility of a breach depends upon the material blocking it," Sharma said. "If there are big boulders at the mouth then overflow will be less intensive and water will gradually flow out. But if there is soft material there, a sudden outburst is possible" he said.

The lake formed behind a landslide late last month that blocked the Pareechu River, a tributary of the River Sutlej in Tibet. China has ruled out controlled blasting of the land slip to allow the water to gradually drain because of the area's mountainous terrain.

Authorities in the northern state of Himachal Pradesh have evacuated more than 3,000 people from eight villages on the banks of the Sutlej following fears that they could be submerged if the lake burst. -Reuters