History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c32.s2.t2.4

v1.c32.s2.t2.4

After selecting the site either in a hilly tract or in plains, the bed of the reservoir in the basin system was strengthened with hard clay. Further, the entire area enclosed by a group of hills or earthern embankments was adjusted to form the bed of the reservoir. The elevation (kūrma) in the middle of the tank bed was totally avoided. Otherwise, the storage capacity of the reservoir would be reduced. The bed of the reservoir at the egress was formed of stony bed along a tortuous line, so that the water issued from it whirled round with great force, forming strong eddies (EI, XIV, p. 108, f.n. 8). It was provided with an inlet and outlet channels and the inlet channel was normally three yojanas distant from its source. In the basin system it was also the practice to carry the flood waters into the basin by canals. Main canals carried the water from a river. Distribution canals fed the water from the main canals into the basin. A dam across the portions of hills was constructed of a firm and compact stone wall. The stones from the quarry were straight and long to withstand pressure and strain. In the mountainous tract the question of an earthern embankment strengthening it with stone facing did not arise; whereas in the level plain it was necessary to throw up earthern banks all around the tank bund.