Recent hydrological response of glaciers in the Canadian Rockies to changing climate and glacier configuration

Mountain snow and ice greatly influence the hydrological cycle of alpine regions by regulating both the quantity and seasonal variations of water availability downstream. This study considers the combined impacts of climate and glaciers changes due to recession on the hydrology and water balance of two high-elevation basins in the Canadian Rockies. A distributed, physically based, uncalibrated glacier hydrology model developed in the Cold Regions Hydrological Modelling platform (CRHM) was used to simulate the glacier mass balance and basin hydrology of Peyto and Athabasca Glacier basins in Alberta. Bias-corrected reanalysis data were used to drive the model. The model calculates the water balance of a glacierized basin, influenced by the surface energy and mass balance, and considering redistribution of snow by wind and avalanches. It was set up using hydrological response units based on elevation bands, surface slope and aspect, as well as changing land cover. Aerial photos, satellite images and Digital Elevation Models (DEM) were assimilated to represent the changing configurations of glacier area and the exposure of ice and firn. Observations of glacier mass balance, snow and glacier ice surface elevation changes at glacier and alpine tundra meteorological stations and streamflow discharge at the glacier outlets were used to evaluate the model performance. Model results indicated that both basins have undergone continuous glacier loss over the last three to five decades, leading to a 6–31 % reduction in glacierized area, a 78–109 % increase in ice exposure, and changes to the elevation and slope of the glacier surfaces. Diurnal temperature ranges are increasing, mainly due to increasing summer maximum daily temperatures. Annual precipitation is not changing much, but rainfall ratios are increasing. Basin hydrology was simulated over two periods, 1965–1975 and 2008–2018, using observed glacier configurations. The results show that changes in both climate and glacier configuration caused changes in melt rates and runoff, and a shift of peak flows from August to July. Glacier melt contributions increased from 27–61 % to 43–59 % of annual discharges. Recent discharges were 3–19 % higher than in the 1960s and 1970s. The results suggest that increased exposure of glacier ice and lower surface elevation due to glacier thinning were less influential in increasing streamflow than climate warming. Streamflow from these glaciers continues to increase.

Impacts of Climate Change on the Water Resources of the Kunduz River Basin, Afghanistan

The Kunduz River is one of the main tributaries of the Amu Darya Basin in North Afghanistan. Many communities live in the Kunduz River Basin (KRB), and its water resources have been the basis of their livelihoods for many generations. This study investigates climate change impacts on the KRB catchment. Rare station data are, for the first time, used to analyze systematic trends in temperature, precipitation, and river discharge over the past few decades, while using Mann–Kendall and Theil–Sen trend statistics. The trends show that the hydrology of the basin changed significantly over the last decades. A comparison of landcover data of the river basin from 1992 and 2019 shows significant changes that have additional impact on the basin hydrology, which are used to interpret the trend analysis. There is considerable uncertainty due to the data scarcity and gaps in the data, but all results indicate a strong tendency towards drier conditions. An extreme warming trend, partly above 2 °C since the 1960s in combination with a dramatic precipitation decrease by more than −30% lead to a strong decrease in river discharge. The increasing glacier melt compensates the decreases and leads to an increase in runoff only in the highland parts of the upper catchment. The reduction of water availability and the additional stress on the land leads to a strong increase of barren land and a reduction of vegetation cover. The detected trends and changes in the basin hydrology demand an active management of the already scarce water resources in order to sustain water supply for agriculture and ecosystems in the KRB.