Global warming is expected to lead to a decline in the availability of water in the Kosi River Basin of Uttarakhand, India, over the next 80 years, according to a study conducted by experts at the Indian Institute of Technology (IIT) Roorkee and the G. B. Pant National Institute of Himalayan Environment (GBPNIHE).

Using the Soil and Water Assessment Tool (SWAT) model together with future projections from five global climate models, the study explores the impact of future climatic changes on water resources in the basin over the course of the 21st century.

As a result of the analysis, the research reveals that there will be an increase in temperature within the basin in all climate change scenarios. For example, the peak temperature of 38.4°C is expected to increase to approximately 41.6°C under moderate emissions and to nearly 43.2°C under high-emission scenarios in 2100. Higher temperatures will likely increase evaporation, thereby affecting water levels in the basin.

Water yield is expected to fall by 4-7 percent by 2100. While evapotranspiration is expected to rise by almost 13 percent, groundwater recharge is estimated to fall by more than 20 percent. Surface runoff is expected to increase by about 20 percent, thus making rainwater flow away without replenishing the groundwater resources below the ground level.

Moreover, drought is also expected to occur more frequently in the catchments and last longer in duration, thereby putting further pressure on the springs and wells that provide water to communities residing in the region. The falling groundwater recharge rate will impact agricultural irrigation systems in the basin too.

Dr I.D. Bhatt, Director of GBPNIHE, said the study found that rising temperatures are altering the hydrological system in Himalayan catchments by increasing evapotranspiration and reducing groundwater recharge. He added that mountain communities dependent on springs and local water sources will require effective water management and adaptation measures to address future climate risks.

Prof. Kamal Kishore Pant, Director of IIT Roorkee, said scientific studies can help policymakers understand how climate change may affect water resources and support the development of long-term adaptation strategies for Himalayan regions.

The researchers recommend measures including watershed management, spring rejuvenation, soil and water conservation, groundwater recharge and nature-based solutions to improve the basin's resilience to future climate impacts.