Glaciers are iconic benchmarks of climate change, and their meltwater represents an important water resource downstream, particularly in spring and summer. A study by researchers from Utrecht University and Chinese Academy of Sciences shows that the melting of seasonal snowpacks in Asia provides an even larger contribution to river streamflow. The water supply from snowmelt has changed considerably over the last 40 years and it will further diminish in the future under continued climate change, with potentially strong impacts on downstream water availability.

  

The authors developed a computer model that simulates snow and compared it with their previous estimates of glacier change. “We see that for all river basins that originate in the high mountains of Asia the total amount of snowmelt is much larger than glacier melt, generally around three to five times as much” says lead author Philip Kraaijenbrink. “Changes to the region’s snowpacks due to climate change can therefore have much stronger impacts on the water balance than retreat of its glaciers.”

 

The scientists predict that there will be considerable losses in the amount of snowmelt in Asia’s rivers, but the degree of future climate change plays a key role. “If we are able to limit temperature rise by the end of the century to 1.5 degrees when compared to pre-industrial levels, as agreed upon in the 2015 Paris agreement, we will see region-wide reductions in snowmelt of only 6%”, says co-author Walter Immerzeel, Professor in Mountain Hydrology at Utrecht University. “However, in more realistic scenarios snowmelt will be reduced by 22% and for specific regions by even more than 50%. Such reductions in meltwater input into the rivers during spring can strongly affect people downstream that depend on that water for irrigation and hydropower.”

 

How these results will impact local water availability remains a research challenge for the future according to the researchers. “This study helps us gain a fuller picture of the water cycle changes at Third Pole.” says co-author Prof. Tandong Yao, co-chair of Third Pole Environment (TPE), an international science program that enabled long-term international collaboration on this topic with support from the science project of Pan-TPE.

 

“Snow and glacier melt are only a part of the total water cycle. Climate change acts on many fronts and controls the changing water supply from the mountains, but there are also socioeconomic developments to consider that affect water demands”, adds Philip Kraaijenbrink. “Our future efforts are on quantifying all processes that impact the mountain water balance to ultimately fully understand the changing system and its impacts on society.”