How did peoples of southern India organize flourishing states and societies in the absence of major rivers?

From the text:

For the most part, however, southern India is an arid land without rivers like the Indus or the Ganges that can serve as sources for large-scale irrigation. Thus, as southern India became more densely populated, irrigation systems became crucial, and a great deal of energy and effort went into the construction of waterworks. Dams, reservoirs, canals, wells, and tunnels appeared in large numbers. Particularly impressive were monumental reservoirs lined with brick or stone that captured the rains of the spring and summer months and held them until the dry season, when canals carried them to thirsty fields. One such reservoir—actually an artificial lake constructed near Bhopal during the eleventh century—covered some 650 square kilometers (250 square miles). Projects of that size required enormous investments of human energy, both for their original construction and for continuing maintenance, but they led to significant increases in agricultural productivity.