<p>Mumbai: Climate change is reshaping the Gangotri Glacier System (GGS), the source of the Ganga River.</p><p>Scientists have modelled Gangotri’s meltwater over four decades and analysed how climate change is reshaping its components.</p><p>Using the high-resolution Spatial Processes in Hydrology (SPHY) model — calibrated with field discharge records, geodetic satellite-derived glacier mass balance data and snow cover maps — researchers analysed the composition of Gangotri’s streamflow from 1980 to 2020. </p><p>The breakdown shows snowmelt dominates, supplying 64 per cent of annual flow, followed by glacier melt (21 per cent), rainfall-runoff (11 per cent), and baseflow (4 per cent).</p>.Massive ground water loss across North India for past two decades, over 700 tmcft lost per year.<p>"Over the last four decades, the composition of flow from the GGS is changing due to climate change, and this study offers the most detailed picture yet of how those changes have unfolded over the past four decades," says lead author Parul Vinze, a PhD scholar at Glaci-Hydro-Climate Lab, IIT Indore. </p><p>“After 1990, the discharge peak in GGS shifted from August to July, linked to reduced winter precipitation and earlier summer melting,” she added. </p><p>Though the flow from GGS is snowmelt-dominated, over time, snowmelt has declined, while rainfall-runoff and baseflow have edged upward, subtly reshaping the basin’s hydrological balance.</p><p>Earlier studies, while valuable, were often limited by shorter records, coarser-resolution climate data, or fewer calibration datasets. This study builds on that foundation, providing a 41-year perspective and a more detailed analysis than has previously been possible, offering clearer estimates of the relative contributions of snowmelt, glacier melt, rainfall-runoff, and baseflow — which have varied across earlier research.</p><p>"Accurate modelling, backed by field data, is key for predicting future water availability in the Himalaya," says Dr Mohd. Farooq Azam, supervisor of the study and Senior Intervention Manager-Cryosphere at ICIMOD and an Associate Professor, IIT Indore.</p><p>“Overall, the Ganga River has relatively less meltwater contribution at a basin-wide scale compared to the Indus Basin, yet at the higher elevations such as the Gangotri Catchment, the runoff is dominated by meltwater, and the observed changes in meltwater seasonality and runoff volume would severely affect hydropower generation and irrigation at higher elevations,” Dr Azam.</p>
<p>Mumbai: Climate change is reshaping the Gangotri Glacier System (GGS), the source of the Ganga River.</p><p>Scientists have modelled Gangotri’s meltwater over four decades and analysed how climate change is reshaping its components.</p><p>Using the high-resolution Spatial Processes in Hydrology (SPHY) model — calibrated with field discharge records, geodetic satellite-derived glacier mass balance data and snow cover maps — researchers analysed the composition of Gangotri’s streamflow from 1980 to 2020. </p><p>The breakdown shows snowmelt dominates, supplying 64 per cent of annual flow, followed by glacier melt (21 per cent), rainfall-runoff (11 per cent), and baseflow (4 per cent).</p>.Massive ground water loss across North India for past two decades, over 700 tmcft lost per year.<p>"Over the last four decades, the composition of flow from the GGS is changing due to climate change, and this study offers the most detailed picture yet of how those changes have unfolded over the past four decades," says lead author Parul Vinze, a PhD scholar at Glaci-Hydro-Climate Lab, IIT Indore. </p><p>“After 1990, the discharge peak in GGS shifted from August to July, linked to reduced winter precipitation and earlier summer melting,” she added. </p><p>Though the flow from GGS is snowmelt-dominated, over time, snowmelt has declined, while rainfall-runoff and baseflow have edged upward, subtly reshaping the basin’s hydrological balance.</p><p>Earlier studies, while valuable, were often limited by shorter records, coarser-resolution climate data, or fewer calibration datasets. This study builds on that foundation, providing a 41-year perspective and a more detailed analysis than has previously been possible, offering clearer estimates of the relative contributions of snowmelt, glacier melt, rainfall-runoff, and baseflow — which have varied across earlier research.</p><p>"Accurate modelling, backed by field data, is key for predicting future water availability in the Himalaya," says Dr Mohd. Farooq Azam, supervisor of the study and Senior Intervention Manager-Cryosphere at ICIMOD and an Associate Professor, IIT Indore.</p><p>“Overall, the Ganga River has relatively less meltwater contribution at a basin-wide scale compared to the Indus Basin, yet at the higher elevations such as the Gangotri Catchment, the runoff is dominated by meltwater, and the observed changes in meltwater seasonality and runoff volume would severely affect hydropower generation and irrigation at higher elevations,” Dr Azam.</p>