Northern India faces the threat of a major power crisis as supply of natural gas through the HBJ pipelines, which caters to a number of power plants in the region, has been discontinued since Thursday morning following heavy flooding at the pipeline's origin point at Hazira in Gujarat. According to official received here till late on Thursday night, over 80 per cent of Surat city was submerged under flood waters and about 1,50,000 people had been evacuated from six flood-affected districts of south and central Gujarat.