One traditional method of irrigation and water retention is through the use of ‘tankas’, which are small tanks that are found underground. Typically they are found within Bikaner houses, and they are built within the main house or within the courtyard. They used to be circular holes that were made in the ground, which were then lined with some fine polished lain. It was in these holes, or small tanks, that rainwater was collected for irrigation purposes or for drinking water. Traditionally, these tankas were decorated with tiles and patterns that made them look attractive. The tiles also served the purpose of keeping the water cool in the midday sun.
A khadin is just another traditional form of irrigation. They were also known as dhoras, and were a rather clever invention that was designed to harvest the surface runoff water for agricultural use. The main feature of this method was that it was incredibly long. It was an earthen embankment that was built across the lower hill sloped which were below the gravelly uplands. There were many spillways and sluices which allowed the excess water to drain off the ground. This khadin system was based on the principle of harvesting rainwater off the farmland, which could then be used back on the farm land to ensure that crops could grow. This system also worked well given that many farmlands quickly became water saturated in hot countries.
Then there are Ahar Pynes. This was a traditional form of harvesting floodwater, and was used in South Bihar. In this area, there is a marked slope from South to North. The soil within this area is sandy and is not able to retain water. The groundwater levels are low too, which means that when rivers in this region swell in the monsoon, the water simply runs off the land at the sides and is not absorbed by the ground.
The ahar is a catchment basin that is embanked on three sides. The 4th side is just a natural gradient of the land itself, and it is able to catch plenty of water.