More than a glacial retreat in the Hindu Kush-Himalaya region (HKH), the shifts in rain and snow due to climate change will likely to have an impact on regional water supplies and groundwater recharge, a study said.
The study was conducted by two Kathmandu-based experts from International Centre for Integrated Mountain Development (ICIMOD) Anjali Prakash and Arun B. Shrestha.
It showed that at lower elevations, glacial retreat is unlikely to cause significant changes in water availability over the next couple of decades, but other factors, including groundwater depletion and increasing human water use, could have a greater impact.
Higher elevation areas could experience altered water flow in some river basins if current rates of glacial retreat continue.
"The shifts in the location, intensity, and variability of rain and snow due to climate change impacts will likely to have a greater impact on regional water supplies and groundwater recharge than glacial retreat," the study said.
The Hindu Kush-Himalaya is one of the most dynamic, diverse, and complex mountain systems in the world, with several rivers and glacial systems making the region a "Third Pole" of the earth, providing fresh water resources to more than 210 million people in the mountains and 1.3 billion people downstream.
Scientific evidence shows that most glaciers in the Hindu Kush-Himalaya region are shrinking, but the consequences of this melt for the regional water systems, especially groundwater, is not clear.
The glaciers are the primary source of groundwater in the HKH, particularly in the mountains. In the foothills, rainfall also contributes to groundwater recharge, but due to the steep topography and rocky surfaces, most of that water flows out of the area and does not infiltrate the subsurface where it can be stored, Prakash and Sreshtha said in the study.
"Groundwater storage in a fractured basement influences the Himalayan river discharge cycle that contributes to countless springs throughout the HKH. Therefore, springs are the major groundwater sources which connect surface and groundwater regimes in the region."
"Increased melting may initially increase the volume of water in rivers, which could mean increased flooding, but as glaciers recede and disappear, the amount of melted snow entering rivers could decrease significantly. Such a situation would result in a substantial decline in the rates of groundwater recharge in some areas.:
"Combined with variations in summer monsoon precipitation and surface water flows, depleted groundwater would lead to highly significant water stress in many parts of the HKH and downstream," the study added.
Spring water has been used by the mountain people since ancient times to meet their basic needs -- but the future of this supply is uncertain. Increasing population, technological advances for withdrawing water, changes in rainfall patterns, and poor water policy frameworks have impeded attempts for better groundwater management.
The "Third Pole" of the HKH continues to provide resources and services to a significant portion of the world's population. But like all ecosystems, near and far, its water systems require greater attention guided through better regional cooperation, the study said.