Which state was the first in India to make rooftop rainwater harvesting compulsory in buildings?

The correct answer is A, of traditional water conservation techniques. A tanka is a covered underground tank, usually sunk in a courtyard or beneath a house in western Rajasthan, into which rain falling on the paved courtyard or the roof is led through a filter and stored for drinking right through the dry months. A khadin, worked out by the Paliwal Brahmins of Jaisalmer in the fifteenth century, is a long earthen embankment thrown across the lower slope of a rocky catchment; runoff collects behind it, soaks the soil, and a crop is raised on the moist bed after the standing water has drained away. Both therefore belong to the family of traditional water harvesting works of the desert, along with the kund, the johad and the baori. Option B is wrong because neither word carries any military sense. Option C is wrong because the folk dances of Rajasthan are Ghoomar, Kalbelia, Terah Taali and Chari. Option D is wrong because, although a khadin supports cropping, the structure itself is a water harvesting work and tanka has no farming meaning at all.

The correct answer is B, Nagaland. Zabo, a word that means impounding runoff, is practised around Kikruma village in the Phek district of Nagaland. Rain falling on a protected forest patch at the top of the hill is caught in ponds on the middle terrace, passed through cattle yards where it picks up manure, and then led to paddy fields lower down that also rear fish, so forest, water, livestock and crops are managed as one linked system. Option A is wrong because the harvesting practice of Meghalaya is bamboo drip irrigation, in which split bamboo pipes carry spring water drop by drop to betel vine and black pepper in the Khasi and Jaintia hills. Option C is wrong because Mizoram is known for its bamboo forests and jhum cultivation rather than for a named harvesting system of this kind. Option D is wrong because Manipur is identified in this topic with the Loktak lake and its floating phumdis, not with zabo.

The correct answer is A, Meghalaya. In the Khasi and Jaintia hills, spring and stream water on a hill slope is tapped and carried through a network of split bamboo pipes, channels and diversion sticks that step the flow down the slope and finally release it drop by drop at the root of each betel vine or pepper plant. The system needs no cement, no pump and no power, and is one of the oldest micro-irrigation methods in the world. Option B is wrong because the traditional work of Kerala in this topic is the surangam, a horizontal tunnel cut into a laterite hill to tap seepage, besides the wooden-cylinder panam keni wells of Wayanad. Option C is wrong because Ladakh is associated with zing, the small tank that collects glacier melt water. Option D is wrong because south Bihar is the home of the ahar-pyne system of channels and embanked reservoirs.

The correct answer is B, a diversion channel that carries water from a river. In the old Magadh region of south Bihar the land slopes gently and the soil holds water poorly, so farmers cut long channels, the pynes, from the flood flow of rivers such as the Phalgu, Sakri and Morhar and led the water across the fields. Option A is wrong because the embanked catchment basin at the tail of a pyne is the ahar, a three-sided reservoir whose fourth side is the natural slope; mixing up ahar and pyne is the standard trap in this question. Option C is wrong because the covered underground drinking water tank is the tanka of western Rajasthan. Option D is wrong because the stepped well reaching down to the water table is the baori or vav of Rajasthan and Gujarat, of which Rani ki Vav at Patan is the best known. The ahar-pyne pair therefore works as channel plus reservoir together.

The correct answer is C, Ladakh. In the cold desert of Ladakh there is very little rain, so the water that matters is glacier melt. Guiding channels bring the melt water down from the snout of a glacier to a zing, a small tank near the fields, where it is held until the afternoon when the melt is strong enough to irrigate. A village water official, the churpun, divides the supply among the households. Option A is wrong because the gravity channel of Himachal Pradesh, in the Kangra region, is the kuhl, which carries glacier and stream water straight to terraced fields rather than storing it in a tank; swapping zing and kuhl is the commonest error here. Option B is wrong because Uttarakhand is associated with the guhl channels and the chal-khal ponds of the hills. Option D is wrong because Sikkim has a very heavy rainfall and is not identified with a named melt water tank of this kind.