Many of the South Indian temples have a temple tank with stone steps. These temple tanks served the purpose of storing the sub soil water as well as the rain water and are considered to be holy. These also helped to hold the rain water and recharge the aquifers. Worshipers either have a purification bath or wash their feet before proceeding to worship the deity.
To quote Dr. Chithra Madhavan an eminent historian and research scholar from an article that was published in “The Hindu”
So, what purpose does a temple tank serve? For one, it is used to bathe the deity and devotees too take a dip in their waters. But the most important aspect of these tanks is water harvesting. Temple tanks help maintain the groundwater level of the surrounding areas; they make sure that wells in their neighbourhood are full.
Sometimes, a tank was an offshoot to the construction of the temple. Mammoth quantities of earth were dug out during the process. These trenches could have been turned into tanks, said Chithra. She went on to point out that though most of these water bodies our kings constructed are in a bad state at present, there are some that continue to serve their purpose. The Mahendra Thadagam (lake) near Arakkonam, built by Pallava king Mahendravarman, irrigates and supplies water to seven surrounding villages even today.
However what is unique about this tank is that this tank is located in the heart of Kumbakonam town. It covers an area of 6.2 acres and is trapezoidal in shape. The tank is surrounded by 16 small Mandapa (shrines) and has 21 wells inside the tank. The names of the wells carry the name of Hindu god Shiva or that of Rivers of India.