The Indira Gandhi canal, formerly the Rajasthan canal, takes water from Harike where the Beas meets the Sutlej and carries it about 650 kilometres into the Thar desert in Rajasthan.
It was begun in 1958 and is one of the largest irrigation projects in the world. It has turned a substantial area of desert into cropland and created a settled agricultural population where there was pastoralism.
It is also the physical mechanism of Punjab's water grievance. Water leaves Punjab at Harike and does not come back, and Rajasthan is not a riparian state of the Sutlej or the Beas.
Waterlogging and salinity have followed the canal in parts of its command area, which is the standard consequence of irrigating desert without drainage.
The canal is either the greatest development achievement in northern India or the clearest case of a state's water being allocated away from it, depending on which side of the Harike headworks the person answering is standing.
It takes water at Harike and runs south west into the Thar, and at over six hundred kilometres of main canal it is one of the largest irrigation works anywhere.
It turned desert into farmland across Sri Ganganagar, Hanumangarh, Bikaner and Jaisalmer, and the settlement followed the canal the way the Punjab colonies followed theirs.
It also produced waterlogging and salinity in the tracts it watered, because desert soils drain badly under flood irrigation, and the corrective drainage has never kept pace.