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Consistent water and glacier mass balance measurements in Central Asia (CoWaG)

Lay summary

Central Asia’s glaciers act as water towers for millions of people by accumulating water in the form of snow and ice and releasing it in the form of meltwater. As the climate is getting warmer, glaciers are retreating which jeopardizes the water tower functionality. Observations from space in the form of stereo-images allow to calculate the “geodetic” glacier volume changes over the large high mountain domain. However, these studies have shown that the spatial and temporal patterns of glacier volume changes over Central Asia are very heterogeneous. These geodetic methods might also have large uncertainty, and they provide only estimates over large time spans, usually in the range of 5 years and longer. As a result, very little is known about the glacier dynamics to short-term weather, and climate variability. This shortcoming limits our ability to produce numerical computer models that could tell us how glaciers will store and release water in the future. This is because observational data is needed for calibration and validation of these models. The importance to have direct glaciological measurements for glaciers in Central Asia has resulted in the re-establishment of key glaciological field sites in recent years, in a multi-national cooperation including several research institutes of Central Asian countries. However, these field sites also provide only annual point-wise ablation and accumulation measurements. In this project, an important step will be made towards a better understanding of how climate variability relates to glacier runoff in Central Asia. The re-established glaciological field sites will be instrumented with additional stream gauges and water quality probes in direct vicinity of the glaciers. Automatic water level gauges and conductivity sensors will be installed, and discharge measurements using dye-tracer experiments will be performed. The water level gauges measure the pressure of the water, which directly relates to the height of the water. In order to convert the water level into discharge, the water level measurements need to be calibrated. This will be done using dye-tracer experiments, in which a fluorescent dye is injected into the stream and its concentration is measured further downstream with a fluorometer allowing to calculate the discharge. These experiments are repeated at different water levels so that a relationship between water level height and discharge can be calculated. The conductivity sensors will provide insights about the source of the water: water coming directly from melting snow and ice has a low conductivity, whereas water that has been in contact with rocks at the base of a glacier or sediments has a high conductivity. The combined measurements will provide very detailed information about the glacier runoff dynamics over the course of an entire year. Automatic weather stations that are part of the existing monitoring network provide the climatic data that will ultimately allow to investigate how climatic parameters (e.g. temperature, solar radiation, rainfall, …) relate to glacier melt in the different climatic zones of Central Asia. The dataset will also provide extremely useful information to improve the numerical models that suffer from the extreme lack of data in Central Asia.

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