Millions of people in Central Asia depend on rivers fed by mountain snow and glaciers. These frozen water stores are especially important in summer, when meltwater helps sustain river flow.

I worked on the Glacier Melting and Water Security in Central Asia project, funded by the Leverhulme Trust, to investigate how climate change could affect this water supply.

I developed snow and glacier melt processes within a large-scale hydrological model and used it to simulate future river flow in the Naryn catchment in Kyrgyzstan, a major tributary of the Syr Darya.

The Naryn catchment in Kyrgyzstan. Modelled river channels are shown in black and glacier outlines derived from Landsat observations in blue.

Testing the model

I evaluated the model against observed river flow at six gauging stations, together with satellite observations of snow cover and glacier extent.

Observed and modelled monthly river flow at six gauging stations in the Naryn catchment. Figure from Shannon et al. (2023).

Future climate

I then ran the model using regional climate projections for Central Asia. Before doing this, I corrected regional biases in temperature and precipitation so the climate data better matched observations.

Regional climate-model temperature and precipitation before and after bias correction.

How river flow could change

By the end of the century under a high-emissions scenario, peak river flow shifts from summer towards spring. Warmer temperatures cause snow to melt earlier, while shrinking glaciers provide less meltwater during summer.

Mean monthly river flow for the historical period and the end of the century. Shading shows uncertainty across the simulations.

Glacier loss

All simulations show substantial glacier retreat.

Under a lower-emissions scenario, mean glacier area falls from around 1,210 km² in 1977 to about 600 km² by the middle of the century. Under a high-emissions scenario, glacier loss continues throughout the century, reaching around 422 km² by 2099.

Projected glacier area under lower- and higher-emissions scenarios, with satellite-derived glacier estimates shown in blue.

Why this matters

As glaciers shrink and snow melts earlier, both the amount and timing of water entering rivers can change. This has important implications for water supply, agriculture and hydropower in regions that depend heavily on snow and glacier-fed rivers.