such historical structures. Another mission is to promote research and development to restore the qanats and other traditional historic hydraulic structures for sustainable development objectives through international co-operation and global transfer of knowledge and technology. According to a report published in 2005 by the Water Resources Base Studies Department affiliated to the Ministry of Energy, there are 15 Regional Water Authorities throughout the country, based in 30 provinces, conducting research projects on water resources in 609 study sites. Each study site is the smallest research unit, containing one or several catchments. Out of 609 study sites, 214 sites with an overall area of 991,256 square kilometers have been declared as restricted regions, and 395 sites with an area of 630648 square kilometers are considered free. 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 3409 million cubic meters is surplus to the aquifer capacity. This deficit in the volume of the aquifer reserves has led to a long-term groundwater level drop of 41 centimeters a year, on average. In the free regions, the number of wells, qanats and springs amounts to 241,091 with an output of 37,527 million cubic meters a year. Therefore, 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. Ab anbar Ab Anbars have a long history in Iran, and there are still some ab anbars remaining today from the 13th century. These reservoirs would be subterranean spaces that were connected to the network of kariz in the city. A typical residential ab anbar would be located in the enclosed garden, have the capacity to hold 50 cubic meters, would be filled once every two weeks, and have its inside surfaces cleaned from sediments once a year (called layeh-rubi). Soon public ab anbars were constructed throughout cities across Persia such as Qazvin, Yazd, Naeen, Kashan, Zavareh, Ray, Shiraz, Herat, Balkh, and others. At the beginning of the 20th century, the number of public ab anbars in Qazvin, for example, was recorded to be 151. Yet Iran still has 30,000 active Qanat systems today. Accounts differ, but the