Tankas a widely cherished traditional water harvesting system in Dwarka has been there since centuries. The traditional art of rainwater harvesting is still being practiced in whole of the city. This indigenous technology has been mentioned in the Jain illustrations and Navtang Acharaya and Hemchandra Acharaya have also written about it. The structure is not only widely used in residential areas but also in temples, dharamshalas, hotels and restaurants.

It is interesting to find that tankas are used in many houses in Dwarka for storing drinking water. The reason for tankas being prevalent in Dwarka is due to the presence of saline water. In order to have sweet water the residents have no option other than to harvest the rainwater.

One of the reasons apart from salinity for the traditional system to be prevalent in Dwarka is that there is no government scheme providing regular water supply to the city. Recently Saini dam (approximately 100 km from Dwarka) has been constructed which supplies water for domestic purposes but its supply highly erratic and unpredictable.

The medical implications of drinking saline water as well as stored water in tankas has also been analysed. According to Dr Bathiya, a medical practitioner as well as a member of Swadhyaya parivar, "The efforts of ancestors should be applauded and treasured because of its potential to provide potable water". He emphasised that the rainwater in the tankas is hygienic and it is ideal for sterlising instruments and other surgical equipments too". He further informed that drinking saline water causes kidney stones among residents of rural and urban areas but no such complications have been reported for stored water in the tankas.

The tankas in Dwarka are like a room at basement of the house. The bottom of the tanka is slightly at a gradient and at the end of the gradient there is a small ‘khadi’ (sump) which is normally of 2 x 2 feet where the water gets accumulated just below of the opening of the tanka. When the entire stored water is utilised then water is drawn from these khadis. To preserve the water a small pot filled with lime is put inside as a disinfectant. The capacity of the tankas is determined by the size of the family. Technological advancement has also been incorporated in the traditional system. People are now using electric motors to draw water from the tankas.

People of Dwarka did not suffer during the recent drought in Gujarat, as there was enough drinking water stored in their respective tankas. Today the situation in Dwarka is such that even while the new house is being constructed 60 per cent of people that are economically sound tend to construct the tanka of approximately 8 feet by 10 feet with an approximate expenditure of Rs 20,000.

Tankas are also prevalent in the temples at Dwarka and Bet Dwarka. The fact that Dwarka is considered as one of the char dhams (main religious centres) in Hindu religion and for a sacrosanct beliefs any activity pursued by the temples is given a lot of respect. Thus having tankas or devoting money towards the construction of tankas is considered as a sacred work at Dwarka. Temples have been responsible for motivating people towards sustaining this traditional form of water harvesting.

In Dwarkadeesh Mandir the stored rainwater is used for the making the prasad (god’s offerings) for the bhagwan (god) and for the bhandar (kitchen) of the temple. The capacity of the tank in Dwarkadeesh temple is approximately 25,000 litres and it normally lasts for one year till the monsoon sets in again. The Swami Narayan Mandir at Dwarka has another sound religious relevance with tankas. The Bet Dwarka temple has tankas inside the premise. There are five temples with each having its individual tankas for day to day activities.