Which river is the longest tributary of the Ganga?

The correct answer is B, Bijnor. After leaving the hills at Haridwar in Uttarakhand, the Ganga enters Uttar Pradesh in Bijnor district and then flows south-east past Kannauj, Kanpur, Prayagraj, Varanasi and Ghazipur before passing into Bihar near Ballia. The state carries the longest course of the river of any state in India.

Option A, Saharanpur, is the district where the Yamuna enters Uttar Pradesh, and it stands at the northern tip of the Ganga-Yamuna Doab, which is why it is the most tempting wrong choice. Option C, Meerut, and Option D, Bulandshahr, both lie in the upper doab and are watered by the Upper Ganga Canal, but the river crosses into the state above them. Fix the pair in memory: the Ganga enters at Bijnor and leaves at Ballia, and the Yamuna enters at Saharanpur.

The correct answer is B, Prayagraj. The Yamuna, the longest tributary of the Ganga, joins it at Prayagraj, and the meeting place is called the Sangam. Tradition adds the unseen Saraswati to the two visible rivers and calls the place Triveni, and it is here that the Kumbh Mela is held. The confluence also marks the southern end of the Ganga-Yamuna Doab.

Option A, Varanasi, stands on the Ganga alone, with the small Varuna and Assi streams after which the city is named. Option C, Kanpur, is a Ganga city of the middle doab and an industrial centre, with no confluence of the two rivers. Option D, Mathura, lies on the Yamuna well upstream, in the Braj region. Remember the doab as a wedge that begins at Saharanpur in the north and closes at Prayagraj in the south.

The correct answer is B, Pilibhit. The Gomti rises from Fulhar lake, also called Gomat Taal, in Pilibhit district of the terai belt, flows south-east through Lakhimpur Kheri, Sitapur, Lucknow, Sultanpur and Jaunpur, and joins the Ganga east of Varanasi. Unlike the Ghaghara or the Ramganga it is not fed by snow, so it is a rain-fed river of the plain itself.

Option A, Shahjahanpur, lies on the Garra, a tributary of the Ramganga. Option C, Bahraich, is on the Ghaghara, which comes from Tibet as the Karnali and is a Himalayan river. Option D, Hardoi, is the district where the Sai rises, and the Sai later joins the Gomti in the Jaunpur region, which makes it a plausible distractor. Keep the plain-fed rivers, the Gomti, the Sai and the Varuna, apart from the Himalayan ones in your notes.

The correct answer is A, Kannauj. The Ramganga rises in the Kumaon Himalaya, enters the plain through Bijnor and Moradabad, waters Bareilly and the Rohilkhand districts and joins the Ganga near Kannauj. It is one of the Himalayan tributaries that keep flowing through the dry months, and the Ramganga dam at Kalagarh is built on it.

Option B, Kanpur, lies downstream of the confluence on the Ganga and is an industrial city, not a meeting point of the two rivers. Option C, Farrukhabad, lies on the Ganga just above Kannauj and is often marked by candidates who remember the stretch but not the exact town; the Kali Nadi joins near there. Option D, Allahabad, is the older name of Prayagraj, where the Yamuna, not the Ramganga, joins the Ganga. Keep the confluence towns in a list: Ramganga at Kannauj, Yamuna at Prayagraj, Tons in Prayagraj district.

The correct answer is B, Hamirpur. The Betwa rises on the Vindhyan plateau in Madhya Pradesh, flows north-east across Bundelkhand past Jhansi and Orchha and joins the Yamuna at Hamirpur. The Matatila dam is built on it, and like other plateau rivers it swells in the monsoon and runs low in summer.

Option A, Etawah, is where the Chambal joins the Yamuna, at Pachnada, the place named for the meeting of five streams. Option C, Banda, is the district in which the Ken joins the Yamuna, near Chilla. Option D, Jalaun, lies in the Betwa and Yamuna country of Bundelkhand but is not the confluence town. The three plateau tributaries are a standard match-the-pair set, so learn them together: Chambal at Pachnada in Etawah, Betwa at Hamirpur and Ken in Banda district.