Lakshmanathirtha River is a principal tributary of Cauvery River
. This river originates from the Brahmagiri (Davasibetta) in the Western Ghats
. Lakshmanathirtha flowing towards the east, has a total length of 131 km. The sub tributary of Lakshmanathirtha River is Ramathirtha. The Krishnaraja Sagar Dam, 3 km long, is constructed at the junction of the three rivers Kaveri, Hemavati and Lakshmanathirtha.