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June 24th, 2017
Via Glacier Hub, a look at water stress in Central Asia:
Glacier mass loss is threatening community livelihoods in Chon Kemin valley, in Central Asia. People in the region “strongly [depend] on glacial melt water for fresh water supply, irrigation and hydropower production…” say Annina Sorg and her coauthors of a paper studying the increased glacial melt in this area and its effect on peak water levels. The study area is of considerable importance, since it contains a number of agricultural villages, and provides water for Bishkek, the capital of Kyrgyzstan. Originating in Kyrgyzstan and flowing into Kazakhstan, the Chon Kemin is an international river.
This Central Asian mountain region is located in the Kyrgyz portion of the Tien Shan Mountains very close to the border of Kazakhstan. The researchers used both old and new methodology to project glacier mass loss. They relied on longer than usual time series of past temperature, snow cover and precipitation data from the area, but they “…also downscaled data from phase five of the Climate Model Intercomparison Project CMIP5…”. This downscaling is very unusual for mountainous Central Asia, allowing them to obtain data at a finer spatial resolution than previous research. The unusual data collection was needed to compensate for the decline in weather station data after the fall of the Soviet Union. Experiments were run with the Glacier Evolution Runoff Model (GERM) so that the researchers were able to record “[g]lacier mass balance, basin evaporation and runoff.”
The authors were able to include many inputs into their parameterizations to obtain what they confidently felt was a realistic result. They calibrated their models to have four future climate scenarios, “…dry-cold, dry-warm, wet-cold and wet-warm future climates…,” which gave a wide breadth of possible glacial lifetimes; in this way, they calculated a range of possible dates for the timing of peak water–the point in time when river flow will be at its highest level. Glacier retreat first leads to an increase of flow, as water stored as glacier ice melts at a higher rate than previously; however, it later leads to a decrease in flow, when the meltwater from the much-reduced glaciers is lower than it had been earlier.
The results showed that there are longer melt season in the Chon Kemin valleys, influenced by warming temperatures and increasing precipitation. The study showed that increased temperatures did not cause a substantial increase in winter runoff, but winter precipitation did increase. This increased snowfall led to even greater, and longer, snow melts in the warmer seasons.
They also found large differences in the scenarios that they ran. In the “glacier friendly” models, the glaciers were able to sustain themselves to roughly less than half their 1955 mass until 2099. In the warmer scenarios, glaciers were gone by 2080. The authors argue that these findings demonstrate the association between a warming climate and increased speed of glacier mass loss. The researchers paid particular attention to the variability of evaporation and how that may play into future glacier mass loss.
The authors argue that peak water is coming relatively soon in this region, either as early as 2020, or near the end of the century, depending on the specific climate scenario. Regardless, peak water levels will be detrimental to the people of the Chon Kemin Valley; signifying the need for further water management programs.
The authors offer the solutions of using nearby reservoirs, using less water intensive crops and restructuing irrigation. They allude to the tensions caused by the international boundaries in this area, drawn in Soviet times, but remain hopeful that this region can come together to solve its impending water shortage. They briefly discuss the region-wide Chu Talas basin agreement as a possible buffer to those political complications.