There are seven classes of water quality according to the WPI, from I (very clean, WPI < 0.3) to VII (extremely dirty, WPI > 10). These include the Chatkal, Ugam, Aktashsav, Kyzylcha and Chimgansay Rivers in different years ranging from Class II (clean) to Class III (moderately polluted) due to heavy anthropogenic pressures in the Chimgan tract. In all but a few areas, this water meets the Uzbek 2000 state standard (O'z DST) 950 on drinking water.