The Ongi River flows through the endorheic Ongi River Basin in Mongolia
and past Arvaikheer. In some particularly wet years, it used to empty into Ulaan Lake,
in most years it dries up earlier. In recent years it has been additionally
threatened by 37 mining operations within the basin, but successful pressure by
Tsetsegee Munkhbayar and the Ongi River Basin Movement helped convince 35 of
the operations to cease explorations and harmful activities in the region. The
water and groundwater in this area may be contaminated with mercury and cyanide
from the mining industry.