The Vembanad lake, the most important of the west coast canal system has a length of 84 Km and an average breadth of 3.1 Km. It covers an area of 204 Sq.Km. Stretching from Alappuzha to Kochi it borders Cherthala, Ambalapuzha and Kuttanad Taluks of Alappuzha district, Kottayam, vaikom and Changanasserry taluks of Kottayam district, Kochi and Kanayannur Taluks of Ernakulam district. Pamba, Achankovil , Manimala, Meenachil and Muvattupuzha rivers discharge into this lake. Pathiramanal, often called the mysterious sand of midnight, having coconut palms and luxuriant vegetation is situated in the centre of this lake. Perumbalam and Pallippuram are the other islands in this lake. The Thannermukkom regulator constructed across Vembanad lake between Thannermukkom and Vechur is intended to prevent tidal action and intrusion of saline water into the lake. It is the largest mud regulator in India.
Stretching between Panmana and Karthikappally, Kayamkulam lake is a shallow lake which has an outlet to sea at Kayamkulam barrage. It has an area of 59.57 Sq.Km., a length of 30.5 Km and an average breadth of 2.4 Km. It connects Ashtamudi lake by the Chavara Panmana canal.
These three rivers flow through Alappuzha district.
It Originates from Mothavara hills in Kottayam district enters the district at Thalavadi village in Kuttanad taluk and passes through Edathua and Champakulam villages and joins the Pamba river at Muttar.The villages of Manimala, Mallappally, Kaviyoor, Kalloppara, Thalavadi, Kozhimukku and Champakkulam lies in the course of the river Manimala. It has a length of 91.73 Km and drainage area of 802.90 Km.
Pamba, the third longest river in Kerala , which has its origin at Peerumedu, after traversing a distance of 177.08 kms. itself in the Vembanad lake. The catchment area of this river is 1987.17 sq. kms. And has a marginal length of 74.02 kms.
Achancovil river is Also Known as Kulallada river.This river entering Alappuzha district at about three miles from the west of Kaipattoor adopts a westerly course till it reaches Chennithala. After that it takes a southwesterly course and joins Pamba at Veeyapuram. The catchment area of this river is 1155.14 sq.kms. And has a marginal length of 32.19 kms.
Alappuzha has a network of canals included in the west coast canal system which are used for navigation. The important canals are Vadai canal, Commercial canals and the link canals between these two canals. Apart from these, there are many inland canals which are mainly used for passenger navigation and commercial purposes.
The lakes are used for inland water transport of passengers and cargo. Inland fisheries have also been flourished in these regions.
Alappuzha has a flat unbroken sea coast of 82 Km in length which is 13.9 % of the total coastal line of the state. An interesting phenomenon of this seacoast during the month of June is the periodic shifting of mud bank popularly known as "Chakara" within a range of 25 Km in Alappuzha-Purakkad coast due to hydrolic pressure when the level of backwater rises during south-west monsoon.