Hot springs and the geothermal energy potential of Jammu & Kashmir State, N.W. Himalaya, India

India has an estimated geothermal power potential of 10,600MWe, but this potential is entirely undeveloped at present. The ‘Geothermal Atlas of India’ prepared by the Geological Survey of India (GSI) in 1991 describes some 340 hot spring sites and identifies more than 300 sites with geothermal potential in at least seven key geothermal provinces throughout India. There are more than 20 hot spring sites in Jammu & Kashmir State, mainly in the Chenab Valley in the Lesser/Central Himalaya, the Kashmir Valley and in the High Himalaya region of Ladakh. At least three localities in the Ladakh region – Chamuthang and Puga in the Indus valley and Panamik in the Nubra Valley – are considered to have geothermal power generation potential of between 3 and >20MWe. The Puga hot spring area, located at the junction of the Indian and Tibetan plates along the Indus Suture Zone, has the greatest potential for the near term development of geothermal energy in the Indian subcontinent. The area exhibits vigorous geothermal activity in the form of hot springs, mud pools, sulphur and borax deposits covering an area of c.15km2. The discharges are concentrated in an east–west elongated area of some 4 km2, near the mouth of the Puga Valley. The Puga geothermal field is bounded by faults and its reservoir rocks consist of granite, gneiss and schist. There is both direct and indirect evidence to support the existence of an active magmatic system at a depth of 5–7km. Geophysical surveys have delineated a conspicuous low resistivity zone below the Puga field. Systematic and comprehensive evaluation of the geothermal potential of the Puga area began in 1973. Thirty-four wells have been drilled in the Puga geothermal field to date, at least 17 of which have resulted in mixed steam and water blow-outs. The discharges from some of the wells have temperatures of more than 120°C. Thermal studies indicate temperatures of more than 220°C at a depth of about 2.5km below the Puga Valley, corresponding to the main reservoir level. Chemical thermometry also suggests a reservoir temperature of 250°C, while reservoir modelling studies suggest temperatures of up to 160°C at a depth of 450m. The high concentration of lithium, rubidium and cesium in the geothermal water has been interpreted as indicating a magmatic source and young granitic intrusions and shallow crustal melting processes have been postulated as the most-likely heat source for the Puga geothermal field. It is estimated that more than