'Tanka' refers to an underground tank commonly used for storing rainwater.

A 'tanka' is an underground tank used for storing rainwater. It is a traditional and sustainable method of water conservation widely used in India.

Key Points:
1. Definition of a Tanka
- A 'tanka' is a large underground tank made of cement or stone that is used to collect and store rainwater.
- It is an ancient water storage system that has been used for centuries in arid and semi-arid regions to ensure a steady supply of water during dry periods.

2. Purpose of a Tanka
- The primary purpose of a 'tanka' is to collect and store rainwater for various uses such as drinking, cooking, and irrigation.
- It helps in reducing water scarcity by conserving rainwater and making it available for use throughout the year.

3. Construction and Design
- A 'tanka' is typically built by excavating a large pit in the ground and lining it with impermeable materials like cement or stone to prevent water seepage.
- The tank is usually cylindrical in shape and has a small opening at the top for rainwater to enter.
- It may also have a filtration system to remove debris and contaminants from the collected water.

4. Collection and Storage of Rainwater
- Rainwater is collected from rooftops or catchment areas through gutters and pipes, which direct the water into the 'tanka'.
- The tank is designed to collect as much rainwater as possible during the rainy season.
- The stored water is preserved underground, maintaining a cool temperature and preventing evaporation.

5. Benefits of Tanka
- Tanka systems are eco-friendly and sustainable as they utilize a natural resource (rainwater) and reduce reliance on other sources of water.
- They help in water conservation and can contribute to the recharging of groundwater tables.
- Tanka water is often cleaner and purer compared to other sources, as it is free from chemicals and pollutants.
- Tanka systems also provide a reliable source of water during periods of drought or water scarcity.

In conclusion, a 'tanka' is an underground tank used for storing rainwater. It is an effective and sustainable method of water conservation that has been used for centuries in India.