Kallada irrigation and Tree crop development scheme is the largest irrigation project in Kerala. The command area of this project is distributed over Kollam, Pathanamthitta and Alappuzha district and coveres Pathanapuram, Kottarakkara, Kollam, Kunnathur, Karunagappally, Adoor, Mavelikkara and Karthikappally Taluks. The scheme was planned to irrigate net cultivable command area of 61630 Ha. During the course of execution few canals including Kayamkulam Branch canal were dropped and now this scheme benefits a net cultivable command area of 53514 Ha in 92 villages. Left and right bank main canals are fully completed.
Kallada Irrigation scheme is a unique project in Kerala, where minor conveyance system consisting of a network of PVC pipe is introduced for supplying water from canal to crops. This is the most efficient system for conveying water to fields, as the loss of water is least. In this system water is conveyed through buried pipe lines and hence compared to field channels, land requirement is less. The works of minor conveyance system for most of canals were completed along with the construction of canals except for a few distributaries.
Main components of the project
Dam at Parappar :- Reservoir is formed by constructing a gravity type masonry dam across Kallada river at Parappar near Thenmala and a saddle earthen dam at Pallamvetty. Gross storage capacity of the reservoir is 504.92 Mm3.
Pick up weir at Ottackal : A pick up weir having a capacity of 17 Mm3 just 5 Km down stream of dam is provided at Ottakkal. The main canals (RBC and LBC) take off from the weir. The tail race water from the power house provided just at the downstream of the dam is collected at weir and used for irrigation. When there is no power generation, the irrigation valves are opened and water collected is at Ottackal.
The details of canals are given below.