Social cause, we were far superior compared to other states especially in karnataka and Andhra and some easter parts. Water Management was well utilised in the past in Tamilnadu. In Ku.Balasubramanaiam's book, I think, it is Kopurak Kalai, he has drawn a map of showing 4 important Biglakes in and around Tanjavur during Chola's rule.
It was well known fact that all our rivers, including Cauvery are monsoon based rivers and most of summer period they were dry. (Remember the old story of Manickavasaka, when he was punished by King for changing horses into foxes, he was asked to stand on the mid of Vaigai river, where the sand must have been very hot in summer). And lakes must have helped to store the waters during summers.
Meantime, in Madras, half of western side of city is full of lake water in 1909.