Rising Rainfall in Western Ghats Over Centuries

Context

The Western Ghats, a UNESCO World Heritage site, is a 1600-km-long mountain range parallel to India’s western coast. Known for its rich biodiversity and significant role in India’s monsoon system, this region has witnessed notable changes in rainfall patterns over the last century. Recent studies reveal an increase in rainfall in the northern parts and a decrease in the southern regions, raising concerns about long-term environmental sustainability and the need for adaptive policies.

Changing Rainfall Trends

Regional Variations

• Northern Western Ghats: From 1931 to 2015, rainfall increased by 2% per decade. This rise is attributed to a northerly shift in the low-level jet stream (LLJ), caused by abnormal sea surface temperature increases in the Arabian Sea and northern India.
• Southern Western Ghats: Rainfall decreased by 3% per decade during the same period. This reduction is alarming as it affects water availability and agricultural productivity.

Decadal Variability

A study analyzing rainfall data from 1901 to 2010 identified three distinct periods:

• 1901–1942: Positive correlation with Indian Ocean Dipole (IOD) changes.
• 1943–1977: Transition phase with moderate variability.
• 1978–2010: High inter-annual variability influenced by Pacific Decadal Oscillation (PDO), leading to alternating excess and deficit rainfall years.

Factors Driving Rainfall Changes

• • Sea Surface Temperature Rise: The increase in sea surface temperatures in the Arabian Sea has influenced the LLJ’s movement, altering moisture distribution across the Western Ghats.

• Global Climatic Influences: 
• • The Pacific Decadal Oscillation (PDO) and Indian Ocean Dipole (IOD) have played significant roles in modulating monsoon rainfall. Post-1978, PDO’s influence became more prominent, correlating with increased rainfall variability.
  • Orographic effects of the Western Ghats continue to shape localized rainfall patterns, especially on the windward side.
• Water Vapor Recycling: Studies using isotopic analysis indicate strong water vapor recycling along the foothills of the Western Ghats, particularly in smaller basins like Swarna. Larger basins like Nethravati show seasonal variability influenced by winter monsoons.

Impacts of Rainfall Changes

• Agriculture: The uneven distribution of rainfall affects crop yields and water availability for irrigation. Northern regions may face challenges from excessive rainfall, while southern areas struggle with deficit.
• Ecosystems: The biodiversity-rich Western Ghats are sensitive to climatic changes. Reduced rainfall in southern regions can threaten endemic species reliant on consistent water availability.
• Water Resources Management: The lack of sustainable water budgeting exacerbates challenges posed by these changes. High demographic pressure and dry pre-monsoon seasons further strain water resources.

Policy Recommendations

• Adaptive Water Management: State governments must prioritize rainwater harvesting through micro-irrigation projects and mini-hydropower initiatives to address regional disparities in rainfall patterns.
• Long-Term Forecasting: Developing decadal predictions for monsoon variability can help policymakers plan better for agricultural and water resource management. Current forecasting systems focus only on short-term predictions.
• Climate Mitigation Strategies: Efforts should focus on reducing sea surface temperature anomalies through global climate agreements and localized measures like afforestation to stabilize atmospheric systems influencing monsoons.

Conclusion

The Western Ghats’ changing rainfall patterns underscore the urgency for long-term environmental policies. While northern regions experience increased wetness, southern areas face alarming deficits that threaten agriculture, ecosystems, and water resources. By adopting adaptive strategies and improving forecasting capabilities, India can mitigate risks associated with intensifying monsoon variability and ensure sustainable development in this ecologically critical region.

Source: The Hindu

UPSC Mains Practice Question

Q. The Western Ghats is one of the eight “hottest hot spots” of biological diversity in the world. Discuss the ecological significance of the region and analyze the challenges in its conservation. Suggest measures for sustainable development in the Western Ghats.

Download as PDF