(a) Explain the impact of tropical cyclones and western disturbances on the climate of India. 20 (b) Examine the critical issues…

(a) Impact of tropical cyclones and western disturbances on India's climate

Tropical cyclones and western disturbances are two major weather systems that alter rainfall and temperature outside the main monsoon flow.

Tropical cyclones form over the Bay of Bengal and Arabian Sea mainly in April–June and October–December. The Bay produces about four times as many as the Arabian Sea, and they strike the east coast. Impacts:

• Heavy rain, strong winds and storm surge over coastal Odisha, Andhra Pradesh, Tamil Nadu and West Bengal, as with Fani (2019) and Amphan (2020), and on the west coast Tauktae (2021).
• They bring much of Tamil Nadu's post-monsoon rain and add water to reservoirs in the south.
• In the monsoon season, depressions bring rain to central India; pre-monsoon cyclones can delay or alter monsoon onset, as with Cyclone Vayu in 2019.
• They cause floods and damage, lower local temperatures after landfall and affect fisheries and agriculture.

Western disturbances are extratropical cyclonic storms from the Mediterranean region, carried east by the sub-tropical westerly jet stream, mainly from December to March. Impacts:

• Winter rain in the north-west plains and snow in the Himalaya, which feeds rivers and is vital for rabi crops such as wheat.
• Cloud cover that raises night temperature before the rain, followed by cold waves after it, and dense fog.
• Floods and cloudbursts when they interact with the monsoon, as in Uttarakhand in 2013 and Kashmir in 2014.
• Pre-monsoon thunderstorms in the north-west.

Together, they supply rainfall in seasons outside the monsoon and increase the variability of the climate.

(b) Critical issues of groundwater resources in India

India is the largest user of groundwater in the world; it supplies over half of irrigation and about 85 per cent of rural drinking water.

Issues:

• Over-extraction: tube wells, free or subsidised power and water-intensive crops (rice, sugarcane) have caused sharp falls in the water table in Punjab, Haryana, Rajasthan, Delhi, Gujarat and Tamil Nadu. A significant share of assessed blocks is over-exploited.
• Quality: arsenic in the Ganga plain (West Bengal, Bihar), fluoride in Rajasthan and Andhra Pradesh, nitrate and uranium in Punjab, and salinity from coastal intrusion.
• Poor recharge: concrete cover, loss of tanks, wetlands and forests.
• Governance: groundwater is tied to land ownership under the Indian Easements Act, 1882; extraction is poorly regulated and data are weak.
• Inequity: richer farmers drill deeper wells; the poor lose access.

Responses: the Atal Bhujal Yojana (2019), Jal Shakti Abhiyan, aquifer mapping, rainwater harvesting and recharge structures, micro-irrigation, crop diversification, power metering and community management.

(c) Structure and relief of the Deccan Plateau

The Deccan Plateau is the triangular tableland of peninsular India, south of the Narmada, between the Western and Eastern Ghats.

Structure: it is part of the ancient Gondwana landmass. The south and east have Archaean crystalline rocks (gneiss, granite), while the north-west is covered by the Deccan Traps, basaltic lava flows erupted in the Late Cretaceous, which weather to black soil. The plateau tilts gently east, so rivers flow to the Bay of Bengal.

Relief: the Western Ghats (Sahyadri) form a continuous, steep western edge with Anai Mudi (2,695 m) the highest peak of the south. The Eastern Ghats are lower and broken by the Godavari, Mahanadi, Krishna and Kaveri. The Satpura and Mahadeo hills bound the north. Within it are the Maharashtra plateau with step-like trap terraces and flat-topped hills, the Karnataka (Mysore) plateau, divided into hilly Malnad and rolling Maidan, and the Telangana plateau. Rivers have cut wide valleys, leaving residual hills, such as Bababudan and Nallamala, and inselbergs.