Context:
• A recent study analysing river flows from 1980–2021 found an 8% increase in streamflow in the Indus basin, while the Ganga basin experienced a 17% decline, highlighting major hydrological shifts linked to climate variability and groundwater extraction.
Key Highlights:
Observed Hydrological Trends
• Indus basin:
- Annual streamflow increased by about 8%.
• Ganga basin: - River flow declined by around 17% during the same period.
Drivers of Rising Indus Basin Flow
• Increased precipitation linked to western disturbances.
• Greater contribution from winter rainfall systems originating in the Mediterranean region.
• Strongest increases observed in:
- Indus River main channel
- Jhelum River
- Chenab River
Variations Within the Indus System
• Some tributaries like the Ravi and Sutlej showed declining flows despite the overall increase.
Drivers of Declining Ganga Basin Flow
• Approximately 10% decline in rainfall in parts of the basin.
• Rising temperatures and atmospheric water demand.
• Excessive groundwater pumping for irrigation.
Groundwater–River Interactions
• Groundwater contributes 50–70% of annual river flow in the Ganga basin.
• Over-extraction has reversed the natural flow between aquifers and rivers in sections of the Yamuna and upper Ganga.
Geopolitical Context
• Changes in Indus river flows intersect with the Indus Waters Treaty (1960) governing water sharing between India and Pakistan.
Relevant Prelims Points:
- Streamflow
- Refers to the volume of water flowing through a river channel over time.
- Western Disturbances
- Extratropical cyclonic storms originating in the Mediterranean region.
- Bring winter rainfall and snowfall to northwestern India.
- Indus River System
- Major tributaries: Jhelum, Chenab, Ravi, Beas, Sutlej.
- Important for agriculture in Punjab, Haryana, and Pakistan’s Indus plains.
- Ganga River System
- One of the largest river basins in the world.
- Major tributaries include Yamuna, Ghaghara, Gandak, Kosi, and Son.
- Indus Waters Treaty (1960)
- Signed between India and Pakistan, brokered by the World Bank.
- Allocates:
- Eastern rivers (Ravi, Beas, Sutlej) to India.
- Western rivers (Indus, Jhelum, Chenab) largely to Pakistan.
Relevant Mains Points:
- Implications for Water Security
- Declining Ganga basin flows threaten agriculture, drinking water supply, and ecosystem sustainability.
- Rising Indus flows may increase flood risks and transboundary water tensions.
- Groundwater Depletion Crisis
- India is one of the largest groundwater extractors in the world.
- Overexploitation disrupts river–aquifer interactions and long-term water availability.
- Climate Change and River Hydrology
- Changing precipitation patterns and rising temperatures are altering river regimes.
- Himalayan rivers are particularly sensitive to glacial melt and changing snowfall patterns.
- Transboundary Water Governance
- Altered hydrological patterns may influence Indus Waters Treaty negotiations and basin management.
- Cooperative water-sharing mechanisms remain essential.
- Way Forward
- Promote sustainable groundwater management and aquifer recharge.
- Improve river basin-level water governance.
- Invest in climate-resilient irrigation practices.
- Strengthen transboundary water cooperation and hydrological monitoring.
UPSC Relevance:
• GS Paper 1 – Indian Geography (River Systems).
• GS Paper 3 – Environment, Water Resources, Climate Change.