The Ruwan Kanya Reservoir is a 3.66 km long earth filled dam with storage capacity of 58 million cubic meters of water annexed to the Tiga Dam to serve as a balancing reservoir located at about 5.1km downstream of the Tiga Dam. The main features of the structure are:

a. Embankment length – 3,600m
b. Maximum dam height – 21.95m
c. Crest Width – 9.14m (max.)
d. Storage capacity – 57.6mil.m3
e. Spillway Type – Concrete with 2Nos. 1.52m wide slots
f. Spillway length – 18.30m
g. Under sluice pipes – 2Nos. 0.914m  pipe

Water released from the Tiga dam through the main canal I goes into the Reservoir and subsequently released to the irrigation sectors through the 18-Kilometer main canal II. The idea of operating this Ruwan Kanya Reservoir is to provide sufficient irrigation to the irrigation area by reducing the transit time as well as guarantee irrigation water supply in the event of emergency repairs on the Tiga dam which may warrant temporary water closure.