 Vertical wells are dug at various points to tap into the groundwater flowing down sloping land from the source, the mountain runoff.The water is then channeled through underground canals dug from the bottom of one well to the next well and then to the desired destination, Turpan's irrigation system.This irrigation system of special connected wells has been claimed to originate in Iran (e.g., the qanat system), to have originated indigenously, or to have been invented in other parts of China .