In the restricted regions there are 317,225 wells, qanats and springs that discharge 36,719 million cubic meters water a year, out of which 3,409 million cubic meters is surplus to the aquifer capacity. in 2005, in the country as a whole, there were 130,008 deep wells with a discharge of 31,403 million cubic meter, 33,8041 semi deep wells with a discharge of 13,491 million cubic meters, 34,355 qanats with a discharge of 8,212 million cubic meters, and 55,912 natural springs with a discharge of 21,240 million cubic meters.
Question: Which type of natural water supply had the smallest cumulative discharge in 2005?
Answer: qanats