Rivers, Lakes and Water Resources

Indus: rises near Lake Mansarovar in Tibet, where it is called Singi Khamban (Lion's Mouth). It flows north-west between the Ladakh and Zaskar ranges and enters Pakistan near Nanga Parbat. Its Punjab tributaries are the Jhelum, Chenab, Ravi (through Chamba, about 720 km), Beas and Sutlej.

• The land between two rivers is a doab: Bist (Beas and Sutlej), Bari (Beas and Ravi), Rachna (Ravi and Chenab), Chaj (Chenab and Jhelum).

Ganga: the Bhagirathi and the Alaknanda meet at Devaprayag to form it. Its tributaries include the Yamuna, the Ghaghara (fed in Nepal by the Tila, Seti and Bheri), the Gandak and the Kosi.

Brahmaputra: called the Tsangpo in Tibet, the Siang or Dihang in Arunachal Pradesh, and the Jamuna in Bangladesh. Its tributaries include the Subansiri, Jia Bharali, Dhansiri and the Lohit. Majuli, in the Brahmaputra in Assam, is the world's largest inhabited river island.

East-flowing (to the Bay of Bengal):

• Mahanadi: rises near Sihawa, Chhattisgarh.
• Godavari: rises at Trimbakeshwar (Maharashtra). Tributaries: Purna, Pranhita (formed by the Wardha and Wainganga), Manjra, Indravati. Its branch the Gautami reaches the sea past Yanam.
• Krishna: rises at Mahabaleshwar. Also the Kaveri and the Penner.

West-flowing (to the Arabian Sea):

• Narmada: rises at Amarkantak and flows through a rift valley. The Sardar Sarovar dam on it serves Gujarat, Madhya Pradesh, Maharashtra and Rajasthan.
• Tapi: rises at Betul and flows through Madhya Pradesh, Maharashtra and Gujarat; tributaries include the Aner, Panzara and Waghur.
• Mahi and Sabarmati, to the Gulf of Khambhat; Kerala's rivers such as the Periyar and Pamba.

Others: the Luni flows from Rajasthan into the Rann of Kutch in Gujarat; the Chambal and its ravines cross Madhya Pradesh, Rajasthan and Uttar Pradesh.

Lakes:

• Wular (Jammu and Kashmir): the largest freshwater lake.
• Chilika (Odisha): the largest brackish lagoon. Pulicat is brackish too. Vembanad (Kerala) is the longest lake.
• Loktak, Bhimtal and Nainital are freshwater lakes.
• Bhopal's Upper Lake, built in the 11th century, is often called Asia's largest artificial lake.

Dams: Maharashtra has the most large dams. A dam can be classed by structure, purpose and height; spillways let surplus water out.

Traditional water harvesting:

• Guls or kuls: channels in the Western Himalayas.
• Khadins: run-off farms of Jaisalmer. Kunds or tankas: covered tanks of Rajasthan. Johads: earthen dams.

The Thar streams flow only after rain and most vanish into the sand. The richest groundwater lies in the loose (unconsolidated) alluvium of the northern plains.