reported to have mentioned about the Quilon port as one of the five ports for Chinese trade. Links with Persia (9th century), Chinese mandarin in 1275 AD, Portuguese in 1502 AD, and the Dutch followed British in 1795 AD are recorded history. Velu Thampi is credited with organizing the rebellion against the British from this place. Access Considering Kollam as the entry city to the lake, access to the lake are to the Thiruvananthapuram International Airport, away and by road to almost all important centres in Kerala and the rest of the country. National Highway 47 (NH 47) passes through the lake periphery not only from Quilon but also to other locations on its bank from Thiruvananthapuram to the northern towns of Kerala. Southern Railways network of lines connects Quilon with all important centres in the rest of the country. Ferry services operate daily to Alleppey and boats operate to all villages located in the canals of the backwater system. The boat jetty is located at about away from the railway station. Famous Paravur estuary and backwaters are just 21 kilometer away from Ashtamudi. Topography Kallada River is a major river discharging into the Ashtamudi Lake. The Kallada river, which originates near Ponmudi from the Kulathupuzha hills Western Ghats is formed by the confluence of three rivers, viz., Kulathupuzha, Chenthurnipuzha, and Kalthuruthipuzha, and after traversing a distance of about through virgin forests finally debouches into the Ashtamudi wetland at Peringalam near Kollam. With a maximum depth of at the confluence, it is Kerala's deepest estuary. Geology Quaternary and Tertiary sediments and sedimentary rocks are the formations in the lake basin and environs. The Quaternary sediments are of marine and fluvial alluvium of recent age. Tertiary sediments comprise laterite, sandstones and clays of Warkalai formation. Hydrology The average annual runoff from the river system into the estuary is reported to be 76 cubic kilometers of freshwater. The basin drainage area is 1,700 km2 (660 mi2) and with an average annual rainfall of 2400 mm (94 in) it discharges 3.375 km3 (2,740,000 ac·ft) of flow annually. It acts as a flood storage lake thus protecting the thickly populated city of Quilon (Kollam) and the coastal land. The Kallada dam built across the Kallada river is 85.3 m high by 35 m long (280 ft by 115 ft) with a reservoir area of 23 km2 (8.9 mi2) with a storage volume of 0.505