the rio uchusuma, a tributary of the rio mauri, originates on casiri. a natural lake called paucarani exists on the southeastern foot of casiri, and the quebrada achuco valley is also located south of casiri, accompanied by wetlands. on the other side, the southeastward-flowing quebrada mamuta lies to the north and northeast of the volcano, and to the northwest lie streams which flow through the lake casiri and the lake liñuma into the rio mauri. volcanic activity has influenced the drainages through the formation of lava dams, altering watersheds.