How did people of southern india organize flourishing states and societies in the absence of major rivers?

There was a well developed and a highly efficient system of water management from the village level upwards in 900-1270 AD. The water tanks which came up during Chola Dynasty were too many but one stand out. Rajendra Chola built a huge tank named Solagangam in his capital city Gangaikonda Solapuram and was described as the liquid pillar of victory. About 16 miles long, it was provided with sluices and canals for irrigating the lands in the neighbouring areas. Another very large lake of this period, which even today seems an important source of irrigation was the Viranameri near Kattumannarkoil in South Arcot district founded by Parantaka Chola. Other famous lakes of this period are Madurantakam, Sundra-cholapereri, Kundavai-Pereri (after a Chola queen).