Dams for control of river flow and for irrigation are also built on the Indian subcontinent itself. One of the oldest of the important dams in India is an earthen structure built about 150 AD on the Kaviri River in the southern region of Cola. This dam, 330 m long and 18m wide, is rebuilt in the 11th century. River traffic is important along the great rivers of central India — the Ganges and the Indus. Later on, the Hindu civilization takes refuge in the south of India when the Turks occupy the north of the country. From the 9th to the 12th century, in particular, the maritime empire of the Cola unifies all the south of India, even temporarily occupying Ceylon. Numerous dams are built, probably under the influence of the earlier developments in Ceylon. One can identify some fifteen important dams dating from the 11th to the 16th century, generally ranging in height from 9 to 24 m and several hundred meters long; however one of them is no less 16 km [302] in length.4 As in Ceylon, these are all earthen dams.
The Indians are good mathematicians (they invented algebra). But ancient Indian writings show few innovations in the domain of physics, which remains aligned with the Greek theory of the four elements.[303] Indian intellectual efforts were more focused on medicine than physics.
In the north of India, the 13th and 14th centuries witness the development of the infrastructures of Delhi,[304] capital of Turkish sultanate between 1192 and 1388. The initial site of the capital being far from the river, the city constructs very large open reservoirs, and directs storm runoff to them through canals. The inhabitants then get their water from these reservoirs. A new site closer to the river Jamuna is chosen for the city between 1320 and 1325. Although a dam and dike are constructed to create a reservoir for this new location, the site is abandoned even before being occupied. The original site of Delhi remains occupied, despite the inconvenience of its distance from the river. Therefore the city continues to depend on its reservoirs. The account of Tangerian Ibn Battuta, who lived in Delhi between 1335 and 1341, gives some idea of the scale of these reservoirs, as well as a sense of their fragility:
“Outside Delhi, one can see an enormous basin that carries the name of the sultan Shams addin Lalmish and serves a supply of potable water for the inhabitants of the city. [….] This basin is two milles (3.5 km) long and half that distance in width. The western part, next to the musalla (a place of prayer), is made of stones that are laid in steps like benches at different heights. Under each “bench” are steps that enable one to get to the water. Beside each “bench” one sees an enormous cupola with seats for those taking walks or others who are just relaxing. In the interior of the basin there is a grand cupola two stories in height, made of sculpted stone. [….] When the basin is dry, sugar cane is grown along the edges, as well as cucumbers. [….] Between Delhi and the residence of the caliph is the basin al-Khasa, even larger than that of the sultan Shams ad-din. It has nearly forty cupolas around its edge.”[305]
Still later the city of Delhi is moved onto the banks of the Jamuna, under the sultan Firuz Shah (1351-1388) because the maintenance of the canals and reservoirs was judged to have become too burdensome. Along with the move came construction of a great bridge-dam on one arm of this river, as well as irrigation works. In the end all these efforts are in vain, for Delhi is razed by the Mongols of Tamerlan in 1398, ten years after the death of Firuz Shah.
