The Khadin system is based on the principle of harvesting rainwater on farmland and subsequent use of this water-saturated land for crop production.
A Khadin is an earthen embankment built across the general slope to store rainwater within the agricultural field. Sluices and spillways allow excess water to drain off.
The size of the Khadin is designed on the basis of local rainfall patterns, catchment characteristics and soil type.
The delineation of catchment should be done on the cadestal/village map so that there is no wastage of water.
The head outlet gate/opening of appropriate size may be provided in the khadin bund for the release of the standing water if any before the rabi sowing.
A structure of 7.5 cm thick layer can be provided over the bund section for protection against wind and rain erosion.
Khadin may be constructed in an area where soil is fine textured, medium to deep with high soil moisture retention capacity. Soil should be free from salinity.
The angle of slopes for the side of the bunds would be governed by the type of soil, bund base width and height.
The embankments can be converted to permanent structures with cement lining
Though site specific, with good management it can make arid wasteland productive.
On an average, the cultivated area under each Khadin is 10-14 ha with an average dam size between 1.2-1.7 m high x 1.0-1.5 m wide and 100-300 meters in length, depending upon catchment area and number of land holdings. Some openings/gates, are usually provided at a proper location for excess water during flood conditions.
For efficient agriculture, size of catchment area is generally fifteen times of the cultivated area. Rainfall of 75-100 mm is sufficient to charge the Khadin soils with sufficient soil moisture content to raise a successful local crop. In the Khadin area, the collected runoff percolates into the ground and with time recharges the subsoil. Of the total runoff collected only 50-60% of the water is utilised.
Shadoof (also called Dhenkli, or Paecottah) is a hand-operated device for lifting water to irrigate land. It uses a lever system to reduce the force needed from an operator
A shaduf comprises of a long wooden pole or bamboo pole which rests on a frame like a sea-saw or a rice thresher (Dheki). At the longer end of this pole hangs a bucket or a leather bag, which is used for lifting water. At the shorter end a weight (stone or bag of sand) acts as the counterweight.
The shadoof is located such that the bucket hovers above the water of a pond or a canal or a well.
The bucket can be lowered by the operator by pulling it down. The counterweight then raises the filled bucket without any effort from the person.
At the end of each movement, the water is emptied out into the irrigation furrows in the required direction
Length of the lever rod on the side of the bucket is much longer than that on the side of the counterweight. Typically, the fulcrum or where the frame meets the pole is located at 1/6th of the length of the pole. i.e. length from the fulcrum to the bucket is 5 times longer than the length from the fulcrum to the counterweight.
Locally available material can be used; e.g. bamboo for the pole, wooden log for the frame, etc.
In improved versions, a self-emptying bucket is used. A tipping action or a bucket with simple flap valves in used to discharge the water.
A shadoof can irrigate 0.1-hectare land in 12 hours.
The pole and bucket may need periodic maintenance.
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