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Water resource in Upper Indus Basin is highly vulnerable to climate change because seasonal snows and glacial melts are the principal components (70%) of river flows in this basin. Here, we apply the concept of Boltzmann–Shannon entropy to long-term discharge records along the main stem of the Upper Indus and its most important tributary Shyok River to determine the relative stability of flows in the four main seasons of the basin. Spring flows are most unstable possibly due to variations in onset of snow melting time in a changing climate. Summer flows, which account for bulk of the annual flows, have remained relatively stable, indicating general stability of the cryosphere of the basin during the past six decades. We draw support of this conclusion from observation of the trend of long-term time series (1962–2013) of summer inflows at the Tarbela reservoir located at the outlet of Upper Indus Basin. Within the summer flow regime, August flows show greatest instability possibly due to changing rate of production of glacial melts under a changing climate. Upper Indus flows are stabilized by flows from the Karakoram where glaciers have either mostly remained stable or gained mass slightly in the recent decades in spite of widespread glacier wastage or ice losses in the western Himalayas. The approach presented here can be used to determine predictabilities of monthly and seasonal flows in water resources management and planning challenged by changes in climate and by land and water usage in concert with economic and social changes. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Summer river flows in central Karakoram conspicuously exhibit rising trends. [•] Rate of loss of glacial storage is approximately 0.04–0.05mm/day/year. [•] Increasing summer precipitation is responsible for nonnegative glacial mass balance. [•] Rising river flows accompany nonnegative glacial mass balance in central Karakoram. [ABSTRACT FROM AUTHOR]

• Constant ice density assumption produces significant bias. • Glaciers in the Indus are losing mass similar to the rest of Asia. • The western and central Karakoram glaciers are losing negligible mass. • Indus Basin contributes about 0.014 mm a−1 to global sea-level rise. Glaciers in the upper Indus supply more than half of the river water, are experiencing significant melting with a debated fate. The recent melting rate is still contained by considerable uncertainties, hindering to estimate precise glacier mass change. Here we present geodetic mass balance results for the whole Indus Basin using SRTM and ALOS 30 m elevation data, improved glacier inventory, optimized glacier surface density, and validation through in-situ differential GPS and ICESat data. Our glacier inventory and derived by improving RGI6.0 boundaries and separated into debris cover and debris free parts. The derived surface elevation changes were converted into annual mass balances using separated density assumptions (four criteria) for debris-covered ice (900 ± 60 kg m−3), debris-free ice (below 20° and 25° slopes (850 ± 60 kg m−3) and above 20° and 25° slopes (600 ± 60 kg m−3)), respectively. The resulting mass balance biased between −0.20 and 0.09 m water equivalent (w.e.) a-1 using an average (850 ± 60 kg m−3) density assumption throughout the Indus Basin. In the western Himalaya and Hindu Kush, the glacier mass losses are less affected by the average density assumption compared to the Karakoram. The western (Hunza) and central (Shigar) Karakoram glaciers show negligible mass losses of −0.02 ± 0.12 and −0.01 ± 0.13 m w.e. a−1 in contrast to the relatively more negative mass balance (−0.26 ± 0.21 m w.e. a−1) in the eastern (Shyok) Karakoram. All the sub-basins exhibit negative mass balances, with the most negative values ranging from −0.34 ± 0.31 to 0.44 ± 0.27 m w.e. a−1 in the Ravi, Chenab and Jhelum sub-basins of the Himalaya. The whole Indus Basin contributes approximately +0.014 ± 0.016 mm a−1 to the global mean sea-level equivalent. [ABSTRACT FROM AUTHOR]

Seasonal and annual water supplies of the rivers originating in the Hindukush-Karakoram-Himalaya (HKH) region of Pakistan are important to manage the Indus basin irrigation system for better agricultural production and its dependent agrarian economy. In this study, we simulated the current and future snowmelt runoff in a poorly gauged river basin of the Hindukush region under Representative Concentration Pathways (RCP) climate change scenarios. Snowmelt Runoff Model (SRM) furnished with satellite snow cover maps and hydro-meteorological data were used to simulate the daily river discharge for the period 2000‒2005. The results indicated that SRM has effectually simulated the runoff in Chitral River with Nash-Sutcliffe model efficiency coefficient of 0.85 (0.84) and 0.88 (0.83) in the basin-wide (zone-wise) application during the calibration and validation periods, respectively. The results obtained under future climate change scenario showed ∼14‒19% increase in mean summer discharge under three mid-21st century RCP (2.6, 4.5 and 8.5) scenarios. While an increase of ∼13‒37% is expected under late-21st century RCP scenarios. This study can help water resource managers to plan and manage peak discharges from the Chitral River Basin in the future and can thus prevent major losses due to floods in the area. [ABSTRACT FROM AUTHOR]