Glacier and runoff changes in the Rukhk catchment, upper Amu-Darya basin until 2050

Abstract

A conceptual hydrological model was set up in the upper Panj catchment, the main tributary of Amu-Darya river. After a manual calibration procedure involving model runs with different restrictions, the model reproduced both daily hydrographs of Tanimas river at the Rukhk gauging station (NSE = 0.86) and the snow water equivalent of the Irkht station (R 2 = 0.85) in a very satisfactory way. Based on two glacier inventories from the mid-20th century (WGI, World Glacier Inventory) and from 2003 (GLIMS, Global Land Ice Measurements from Space), a simple parameterization scheme based on steady state conditions was applied to infer the ice volumes and glacier areas for these different time periods. Assuming temperature rises of 2.2°C and 3.1°C, which mark the extreme values of regional climate scenarios, the same method was used to extrapolate glacierization to the year 2050. The results show that these temperature rises will reduce the current glacier extent of 431 km 2 by 36% and 45%, respectively. To assess future changes in water availability, the hydrological model input was modified according to the regional climate scenarios and the resulting glacier changes. The use of an elevation distributed deglacierization pattern is a clear improvement over methods used previously, where the impact on runoff was tested by excluding either the lower half or the total glacier area. The runoff scenarios reveal only a slight reduction in annual runoff, because the glacier area decrease is almost balanced out by enhanced melt rates. However, there is an important seasonal shift of water resources from summer to spring, unfavorably affecting agriculture and irrigation in the lowlands.

Hydrologic Regime Changes in a High-Latitude Glacierized Watershed under Future Climate Conditions

“…PET is calculated for non-glacierized regions using the Hamon equation [2]. In the Copper River application, the Hamon coefficient was calibrated to Penman Monteith PET calculated using the Valiantzas equations [3,4] with CFSR data.…”

Sensitivity analysis and implications for surface processes from a hydrological modelling approach in the Gunt catchment, high Pamir Mountains

“…The hydrological regime is reported to be snowand glacier-melt-dominated (Lutz et al, 2014;Kure et al, 2013;Tahir et al, 2011), albeit quantitatively largely unconstrained. Increasing demand for water and assumed changes in hydrological regimes of glaciated catchments with respect to a change in climatic conditions (Immerzeel et al, 2009;Hagg et al, 2013), as well as the inherent increased risks, demand for a better understanding of the processes governing surface flow in the region.…”

“…The few hydrologic studies in the Pamirs are hence basically glacier melt/snowmelt-runoff models that relied on in situ data (Hagg et al, 2007) and, more recently, on GCM (global climate model) data output (Kure et al, 2013;Hagg et al, 2013;Lutz et al, 2013) including future climate change scenarios. In contrast with the qualitatively agreeing hydrological studies, studies focusing solely on glaciers in the Pamirs show ambiguous results.…”

High uncertainty in 21st century runoff projections from glacierized basins

“…Numerous model studies for a wide range of climatic settings have been performed, estimating future trends in the hydrology of glacierized basins (e.g., Juen et al, 2007;Stahl et al, 2008;Weber et al, 2010;Hagg et al, 2013;Bavay et al, 2013;Ragettli et al, 2013). As a robust result, a shift in the runoff regime and a decrease in melting season discharge is found on the long run.…”