Abstarct: Biarjomand city is located 106 km southeast of Shahrood. This city belongs to the region of desert margin which its climate is hot and arid. Such that the annual precipitation and the mean temperature of this city 111 mm, 17.5 ◦c are respectively. From geological point of view, this area is located in central flat of Iran and the main formations in this area include orbitolinna limestone in the west and south, and quaternary sediments within Biarjomand plain. Because of the climate of this region, there is no perennial river and the water for different consumptions is supplied by groundwater. Agriculture is the main activity of people in this area and qanats has important role in irrigation of arable lands. In order to assess the quantity and quality of qanat water in Biarjomand region (including Taher-Abad, Derani, Qanat-Bozorg, Ghale-Bala, Yazdoo, Dezian and Par) for one hydrologic year, the values of discharge, electrical conductivity, water temperature and pH were measured in situ and the major cations and anions measured in the lab. The obtained results show that in mountainous qanats, because of short length of qanat and locating in the limestone formations, the quality of qanat water are higher than that for plain qanats (the electrical conductivity mean of mountainous and plain qanats are respectively 350 and 1037 μs/cm). Despite of high quality in the mountainous qanats comparing to plain qanats, their discharges is lower those that in plain qanats (such that the discharge of mountainous and plain qanats are respectively 8.3 and 21.6 L/s). The temporal variations of chemical characteristics for all qanats are little, but the variations of discharge in mountainous qanats are relatively high. Moreover, the biological pollution of some qanats in the study region was measured which illustrates that some biological pollution in plain qanats due to their large underground tunnels and some open shafts in these qanats.