Mangroove forest. The Madu River Safari is popular activity that has to be on the to do list of any respectable Sri Lankan holiday goer. This unforgettable activity lasts for over two hours and gives a visitor a chance to travel the secretive passages through the mangrove forests and see the ecology. Madu Ganga is a minor watercourse which originates near Uragasmanhandiya in the Galle District of Sri Lanka, before widening into the Madu Ganga Lake at Balapitiya. The river then flows for a further a 4.4 km before draining into the Indian Ocean. It is located 88 km south of Colombo and 35 km north of Galle. Sri Lanka.