In which of the following States, the area under Tube-well irrigation is the highest?

The correct answer is C) Uttar Pradesh. Tube-wells are the main source of groundwater irrigation, and UP leads India in both the number of private and state tube-wells and the total area they irrigate. Its thick alluvial aquifers in the Ganga-Yamuna plain allow shallow and medium tube-wells to work at low cost.

• Punjab is wrong on absolute area. Its share of irrigated land from tube-wells is very high, close to nearly all of its irrigated area, but the state is much smaller than UP, so its total tube-well area is lower. Candidates confuse percentage share with absolute area.
• Haryana is wrong for the same reason. It has high groundwater dependence but a smaller base.
• Bihar is wrong. Its irrigation depends more on canals and surface sources, and its tube-well coverage is lower than UP's.

The concept here is the difference between canal and groundwater irrigation. For Mains (GS-III, water resources), this links to over-exploitation of groundwater in Punjab and Haryana and to the Central Groundwater Board's critical-block data. Figures from the Minor Irrigation Census and Agricultural Statistics are updated periodically, so check the latest edition before quoting numbers.

Trap: choosing Punjab because it is famous for tube-wells. Read whether the question asks for absolute area or percentage share.