Someswari is the largest and the second longest river in the West Garo Hills District
. Locally known as Simsang, the river starts from Nokrek peak and runs towards east, passing through Rongrengiri, Williamnagar the headquarters of East Garo Hills District
, Nongalbibra, Siju
, Rewak and finally
the headquarters of South Garo Hills District
. The lower course of the river has many deep pools and falls. The chief tributaries are Chibok, Rongdik, Rompa and Ringdi rivers.