Early 21st century snow cover state over the western river basins of the Indus River system

Abstract

In this paper we assess the snow cover and its dynamics for the western river basins of the Indus River system (IRS) and their sub-basins located in Afghanistan, China, India and Pakistan for the period 2001-2012. First, we validate the Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow products from Terra (MOD10A1) and Aqua (MYD10A1) against the Landsat Thematic Mapper/Enhanced Thematic Mapper plus (TM/ETM+) data set, and then improve them for clouds by applying a validated non-spectral cloud removal technique. The improved snow product has been analysed on a seasonal and annual basis against different topographic parameters (aspect, elevation and slope). Our results show a decreasing tendency for the annual average snow cover for the westerlies-influenced basins (upper Indus basin (UIB), Astore, Hunza, Shigar and Shyok) and an increasing tendency for the monsooninfluenced basins (Jhelum, Kabul, Swat and Gilgit). Seasonal average snow cover decreases during winter and autumn, and increases during spring and summer, which is consistent with the observed cooling and warming trends during the respective seasons. Sub-basins at relatively higher latitudes/altitudes show higher variability than basins at lower latitudes/middle altitudes. Northeastern and northwestern aspects feature greater snow cover. The mean end-of-summer regional snow line altitude (SLA) zones range from 3000 to 5000 m a.s.l. for all basins. Our analysis provides an indication of a descending end-of-summer regional SLA zone for most of the studied basins, which is significant for the Shyok and Kabul basins, thus indicating a change in their water resources. Such results are consistent with the observed hydro-climatic data, recently collected local perceptions and glacier mass balances for the investigated period within the UIB. Moreover, our analysis shows a significant correlation between winter season snow cover and the North Atlantic Oscillation (NAO) index of the previous autumn. Similarly, the inter-annual variability of spring season snow cover and spring season precipitation explains well the interannual variability of the summer season discharge from most of the basins. These findings indicate some potential for the seasonal stream flow forecast in the region, suggesting snow cover as a possible predictor.

Future Water Availability from Hindukush-Karakoram-Himalaya upper Indus Basin under Conflicting Climate Change Scenarios

“…Worth noting fact is that substantial reduction in the glacier melt, aside changes in precipitation that are also positive, indicates a positive change in the frozen water resources of the UIB. Such finding is largely consistent with the prevailing changes depicted from the long-term observed streamflow record ( Figure 5) and with the reports of anomalously positive or stable glacial mass balances and extents [20,22,[27][28][29]31,[33][34][35], increasing snow covers and falling end-of-summer regional snow line altitudes [20,22,25,26], and subsequent reduction in the melt season discharges [4,19]. On the other hand, a decrease in the glacier melt and in the overall discharge is in direct contrast to the reports from earlier studies, which addressing only partially the climatic uncertainty over the UIB assess its future water availability under warmer climates [5][6][7][8]90], and suggest rather enhanced glacial melt and rise in the water availability throughout the 21st century.…”

“…Furthermore, the areal extent of the eastern Karakoram glaciers has been reported to be growing since the end of 1980s [29]. A significant falling trend of the end-of-summer regional snow line altitude for the eastern Karakoram over the period 2000-2012 also indicates a positive change in the high-altitude frozen water resources therein [25]. For other main cryospheric regions of the UIB, the studies consistently report and support cooling phenomenon [4,17,19,21,27,28,30,35,36,75,76].…”

“…For other main cryospheric regions of the UIB, the studies consistently report and support cooling phenomenon [4,17,19,21,27,28,30,35,36,75,76]. Over the whole UIB, increasing snow cover in a recent decade [25,26] and conflict of tree-ring based paeleoclimatic Karakoram summer temperatures with the hemispheric warming for recent five centuries [23] have also been reported.…”

“…Such obvious indications of prevailing hydroclimatic changes and their continuation emphasize the use of a plausible climate change scenario, at least for the near-future. Earlier, it has been argued that the climate change scenarios (temperature increase, glacier area decrease) adopted by previous studies are not relevant at least for the near-future and may only be realized in the far-future with no time stamp attached [25]. Hence, in order to address larger spectrum of future climatic uncertainty, two plausible hypothetical climate change scenarios have been considered; one representing the continuation of prevailing contrasting climatic conditions while other consistent with the global warming patterns.…”

Assessment of methods for seasonal streamflow forecasting in the Upper Indus Basin of Pakistan

“…The UIB's tributaries include the Indus at Kharmong: Shigar, Shyok and Astore in the Karakoram Himalaya, the Jhelum, Chenab, Ravi and Sutlej in the western Himalaya, and the Hunza, Gilgit, Kabul, Swat and Chitral in the Hindu Kush mountains (Figure 1). These basins can be classified as having a flow regime that is either glacier-melt dominated (Hunza, Shigar and Shyok) or snow-melt dominated (Jhelum, Kabul, Gilgit, Astore and Swat) (Hasson et al, 2014). The predominant source of flow in the UIB is snowmelt, 20 followed by glacier melt as a secondary source, with 80% of flow occurring during the June-September summer period.…”