Gangotri Glacier Study Reveals Earlier Snowmelt Trends

Gangotri Glacier Snowmelt Latest News

• A recent study has reconstructed the long-term discharge flow of the Gangotri Glacier System (GGS), the source of the upper Ganga basin feeding the Bhagirathi River in the central Himalayas. 
• With climate change driving faster glacier melt globally, glaciologists are closely examining how changes in Gangotri’s discharge patterns could affect water availability, river flow, and long-term sustainability of the region’s ecosystems and livelihoods.

Composition of the Gangotri Glacier System (GGS)

• The GGS comprises four glaciers — Meru (7 km²), Raktavaran (30 km²), Chaturangi (75 km²), and the largest, Gangotri (140 km²). 
• Together, the system spans 549 km², with about 48% glacierised area, across elevations from 3,767 m to 7,072 m. 
• The GGS receives precipitation from western disturbances in winter (October–April) and the Indian summer monsoon in summer (May–September). 
• Seasonal rainfall (May–October) averages 260 mm, with a mean temperature of 9.4°C recorded between 2000–2003.

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New Study on Gangotri Glacier System (GGS)

• The Hindu Kush Himalaya (HKH) holds vital snow and ice reserves that feed major rivers like the Indus, Ganga, and Brahmaputra, sustaining millions of lives. 
• In recent decades, climatic changes have altered the cryosphere and hydrological cycles, leading to faster glacial retreat and shifting seasonal discharge patterns. 
• While most modelling studies focus on large river catchments, it is difficult to separate the impacts of snowmelt and precipitation there. 
• Smaller systems like the GGS allow for more precise assessments, making it a preferred choice for hydrologists and climate scientists. 
• However, long-term discharge analysis and understanding climatic drivers have remained limited. 
• To address this, a new study titled “Hydrological Contributions of Snow and Glacier Melt from the Gangotri Glacier System and Their Climatic Controls Since 1980” was conducted.
• The study, published in the Journal of the Indian Society of Remote Sensing, provides deeper insights into GGS’s meltwater contributions and climate influences.

Key Findings of the Study

• The study combined the Spatial Processes in Hydrology (SPHY) glacio-hydrological model with the Indian Monsoon Data Assimilation and Analysis (IMDAA) dataset (1980–2020) to reconstruct GGS discharge trends. 
  • SPHY model is a hydrological modelling tool suitable for a wide range of water resource management applications.
• It found that maximum discharge occurs in summer, peaking in July (129 m³/s). 
• The mean annual discharge was estimated at 28±1.9 m³/s, primarily from snow melt (64%), followed by glacier melt (21%), rainfall-runoff (11%), and base flow (4%).
• A decadal analysis revealed a shift in discharge peaks from August to July after 1990, linked to reduced winter precipitation and enhanced early summer melting. 
• The highest volumetric increase (7.8%) occurred between 1991–2000 and 2001–2010. 
• While mean annual temperatures rose, there was no significant trend in precipitation or glacier melt. 
• Snow melt declined due to shrinking snow cover, whereas rainfall-runoff and base flow increased. 
• The analysis highlighted that summer precipitation was the main driver of annual discharge, followed by winter temperature.

Implications of the Study on GGS

• The findings highlight warming-induced hydrological changes in the Gangotri Glacier System (GGS), with increasing rainfall run-off and base flow. 
• This aligns with the 25% excess rainfall observed in North India’s summer monsoon (June–August), which has caused frequent floods in Uttarakhand, Jammu, and Himachal Pradesh. 
• While such events are often hastily termed “cloudbursts” without scientific evidence, climate change does raise the risk of extreme rainfall. 
• The study stresses the need for sustained field monitoring and advanced modelling to improve water resource management in glacier-fed river basins, ensuring resilience against future hydrological and climatic shifts.

Source: TH | DTE