In many high altitude river basins, the hydro-climatic regimes and the spatial and temporal distribution of precipitation are little known, complicating efforts to quantify current and future water availability. Scarce, or non-existent, gauged observations at high altitudes coupled with complex weather systems and orographic effects further prevent a realistic and comprehensive assessment of precipitation. Quantifying the contribution from seasonal snow and glacier melt to the river runoff for a high altitude, melt dependent region is especially difficult. Global scale precipitation products, in combination with precipitation-runoff modelling may provide insights to the hydro-climatic regimes for such data scarce regions. In this study two global precipitation products; the high resolution (0.1 degrees x 0.1 degrees), newly developed ERA5-Land, and a coarser resolution (0.55 degrees x 0.55 degrees) JRA-55, are used to simulate snow/glacier melts and runoff for the Gilgit Basin, a sub-basin of the Indus. A hydrological precipitation-runoff model, the Distance Distribution Dynamics (DDD), requires minimum input data and was developed for snow dominated catchments. The mean of total annual precipitation from 1995 to 2010 data was estimated at 888 mm and 951 mm by ERA5-Land and JRA-55, respectively. The daily runoff simulation obtained a Kling Gupta efficiency (KGE) of 0.78 and 0.72 with ERA5-Land and JRA-55 based simulations, respectively. The simulated snow cover area (SCA) was validated using MODIS SCA and the results are quite promising on daily, monthly and annual scales. Our result showed an overall contribution to the river flow as about 26% from rainfall, 37-38% from snow melt, 31% from glacier melt and 5% from soil moisture. These melt simulations are in good agreement with the overall hydro-climatic regimes and seasonality of the area. The proxy energy balance approach in the DDD model, used to estimate snow melt and evapotranspiration, showed robust behaviour and potential for being employed in data poor basins. (c) 2021 Published by Elsevier B.V.

The degradation of mountain permafrost under climate warming may alter the runoff regime of high mountainous catchments. In this study, we evaluated the influence of permafrost on the hydrological regime using hydrological signals in the Yeniugou Basin located in a mountainous permafrost region in the Qilian Mountains of the northern Tibetan Plateau (TP). The effect of permafrost degradation on the hydrological response was assessed based on 28 years of runoff and meteorological data. The results indicated that the investigated region exhibited a large increase in annual surface ground temperature from 1979 to 2006, with almost unchanged precipitation and evaporation potential. The winter runoff levels exhibited a significant decreasing linear trend, whereas the annual runoff and runoff in other seasons did not show any distinct linear trends. According to a comprehensive analysis of the relationships between winter runoff and meteorological factors, the ratio of maximum(Q(max)) and minimum (Q(min)) discharge, the recession coefficient and baseflow separation, and the reduced winter runoff were significantly correlated with thawing of permafrost. However, due to a time-lag response of climate forcing to permafrost thawing, some of these changes are undetectable over a short period. This study provides preliminary data on cold region hydrology and its response to climate change. (C) 2016 Elsevier B.V. All rights reserved.

Global warming is most pronounced in high-latitude regions by altering habitat conditions and affecting permafrost degradation, which may significantly influence tree productivity and vegetation changes. In this study, by applying a space-for-time approach, we selected three plots of Larix gmelinii forest from a continuous permafrost zone in Siberia with different thermo-hydrological soil regimes and ground cover vegetation with the objective of assessing how tree growth and productivity will change under different stages of permafrost degradation. A tree-ring multi-proxy characterization of mature trees was used to identify shift in ecophysiological responses related to the modified plant-soil system. Variability of tree-ring width (1975-2009), stable isotope ratios (oxygen and carbon, 2000-2009) and xylem structural characteristics (2000-2009) under climatic conditions of particular years indicated that an increased depth of the soil active layer will initially lead to increase of tree productivity. However, due to an expected water use increase through transpiration, the system might progressively shift from a temperature to a moisture-limited environment. (C) 2015 Elsevier GmbH. All rights reserved.