Assessment of geothermal reservoirs temperature using dissolved silica geothermometry: A case study from Garhwal Northwest Himalaya, India

The growth in population and their reliance on modern technology stress more and more on energy, which is dwindling in India. Mostly, the demand of energy is met by fossil fuels that produce CO2 - a greenhouse gas and is responsible for global warming. Again, we produce only 30% of our energy requirement indigenously and spend huge money to import the remaining. This necessitates an alternate source of energy for sustainable development with reduced impact on climate change or environmental hazards. Under this scenario, it is envisaged to tap renewable and unconventional green energy reserves. The geothermal fields in the northwest (NW) Himalaya offer renewable energy resources that have great potential for generating electricity and heating/cooling purposes. The present work aims for estimating the subsurface reservoir's temperature based on dissolved silica geothermometry to harness this energy that can meet the local requirements in the Himalaya and adjoining regions. For this, we have investigated the silica-water reactions in low to moderate (30 degrees C to 93 degrees C) surface temperatures at 20 active geothermal springs in the Garhwal NW Himalaya. The results of modified silica-quartz with no steam loss and silica chalcedony methods show an average minimum reservoir temperature of 81 degrees C at Matli and the highest temperature of 146 degrees C at Jankichatti sites. The estimated reservoir temperatures of geothermal springs are likely to be the minimum temperature. The average reservoir temperature is estimated to be 125 +/- 10 degrees C, indicating that the geothermal fields in the Garhwal (Uttarakhand) Himalaya possess low to medium enthalpy resources. No major variation in geochemistry has been found in the data during the last fifty years (1970-2020). The geothermal resources are active, as manifested by hot springs and encrustations around the springs. It has been planned for converting the geothermal energy into electricity at Tapoban in the Garhwal Himalaya. The geothermal fields can be monitored on regular basis by observing variation in hydro-chemistry of discharges.