Water Harvesting in Thar Desert

In the sandier tracts, the villagers of the Thar Desert had evolved an ingenious system of rainwater harvesting known as kundsor kundis. Kund, the local name given to a covered underground tank, was developed primarily for tackling drinking water problems. Usually constructed with local materials or cement, kundswere more prevalent in the western arid regions of Rajasthan, and in areas where the limited groundwater available is moderate to highly saline. Groundwater in Barmer, for instance, in nearly 76 per cent of the district’s area, has total dissolved salts (TDS) ranging from 1,500-10,000 parts per million (ppm). Under such conditions, kunds provided convenient, clean and sweet water for drinking.

The kund consists of a saucer-shaped catchment area with a gentle slope towards the centre where a tank is situated. Openings or inlets for water to go into the tank are usually guarded by a wire mesh to prevent the entry of floating debris, birds and reptiles. The top is usually covered with a lid from where water can be drawn out with a bucket.

The catchment areas of kunds were made in a variety of ways using locally available sealing materials such as pond silt, murrum, charcoal ash, and gravel. After clearing the soil surface of vegetation, the land was given a smooth gradient of 3-4 per cent towards the kund and the cleared surface was lined with pond silt obtained from nearby talabs or nadi beds. A local technique was used after the first shower of the monsoon season to make this layer semi-permeable. In places where a calcium-carbonate zone was available below the soil surface at a shallow depth, water-proofing of the soil was done with murrum. After clearing the soil surface of vegetation, a thin layer of murrum was spread over it. With the onset of the monsoon, sheep and goats were made to move over the murrum repeatedly till the surface was compacted and became semi-impermeable. During this process water was also sprinkled, if needed. Although charcoal ash was not used as a surface sealing material by itself, it was used to repair the catchment area made of pond silt and murrum. As the ash settled down, it filled the pores making the surface water-proof. In certain areas, where rock exposures occurred, kund catchments were made of gravel layers. Such catchments were, however, very few, depending on the availability of gravel.

The benefits of kunds during inadequate rainfall have been in doubt. However, a study which analysed daily rainfall records for 14 years in three or four raingauge stations in each of the 11 desert districts of Rajasthan puts these doubts to rest. It was calculated that there was effective rainfall (25 mm) on at least four to six days every year, except in Jaisalmer, Pali and Sikar.With this rainfall, a kund with a catchment of 100 sq km could easily collect 10,000 litres of water. Kunds with a diameter of 56 m and a catchment area of 2,463 sq m will bring in 246,000 litres of water. Even if we assume that only 40-50 per cent of rain will turn into runoff, a kund can still store 0.1 million litres of water. The rainfall data collected showed that areas with 100 mm of rainfall can use the kund system effectively. Even if the kunds do not collect sufficient water they can be used as water reservoirs which can be filled by transporting water through water tankers.