Masi Maham and holy theerthams of Mahamaham tank, Kumbakonam

The holy city of Kumbakonam in Thanjavur district of Tamil Nadu has innumerable temples dedicated to god Shiva, god Vishnu and  goddess Shakti. This place is synonymous with Mahamaham tank where the annual Masi Maham festival takes place annually that is attended my people in thousands. The most important festival is Mahamaham that takes place every 12 years during the month of Masi (February - March). It attracts as much crowd as Kumba Mela of North India (of course, minus fully barred sadhus) does. Located in the main part of the city, there are 16 mandapas around the tank that were built by Govinda Dikshitar, the minister of Nayak king Vijaya Raghunatha of Thanjavur Nayak dynasty out of the benevolence of the Nayak ruler. Krishnadeva Raya (1509–1529 CE) is believed to have witnessed the Mahamaham festival during this time and on that occasion he made valuable donations to the temples. 
Mahamaham tank, Kumbakonam.. tripradvisor
Both in the annual Masi Maham festival as well as the Mahamaham festival held every 12 years, Theerthavari is an important event. The procession deities of 12 Shiva temples of Kumbakonam  reach the banks of the Maham tank for abisekham / immersion in the holy tank and  likewise the deities of  five Vishnu temples arrive at the Chakra Ghat on the banks of the river Cauvery for Theethavari. 

On the Masi Maham days, devotees in thousands take a holy dip at various theerthams to get blessings from their forefathers, absolve of all  sins committed by them and get salvation from the cycle of rebirth and  death.

kumbakonam location map. tripadvisor

The following are the various Theerthams - holy water and their religious importance:

Vayu Theertham: Deliverance from sufferings.

Ganga Theertham: Attain Kailash mukthi.

Brahma Theertham: Deliverance from sins.

Yamuna Theertham: Earning of wealth and gaining prosperity.

Kubera Theertham: Getting all types of wealth to lead a peaceful and self contended life. 

Godhaveri Theertham: Success in planning.

Esanya Theertham:  Achieving our dream.

Narmada Theertham: Deliverance from  sins.

Indira Theertham: Attaining heaven.

Saraswathi Thertham: Gaining Gnanam / wisdom.

Agni Theertham: To be freed from sins for ever.

Cauvery Theertham: To get rid of evil thoughts and diabolic mind.

Yama Theertham: Freedom from Klalapurusha's sentencing. Tobe freed from the fear of death.

Kumari Theertham: Equal to conducting 16000 Aswamatha Yagam.

Niruthi Theertham: Freedom from evil spirits / forces. 

Payodhini Theertham: Equal to possessing the divine cow Kamadhenu.

Deva Theertham: Getting rid of all kinds of sins. Sarva Pava Vimochanam.

Varuna Theertham: Attaining the state of being free from human bondage.

Sarayu Theertham: To be free from all kinds of woes,setbacks and anxiety.