The Kavvayi River basin is located between 120 05â to 120 15â North latitude and 750 05 â to 750 20â East longitude. It spreads over the district of Kannur and Kasargod.
It has a total area of 164.76 km2 covering 14 villages spread over 9 local bodies in the two districts. Kavvayi River or Thattar River emerges from the Cheemeni Kunnu at elevation 114 m. above MSL having a length of 31 km and joining directly to Kavvai backwater. Kavvayi River is typical among the 14 midland-originated rivers in Kerala. It has a watershed area confined to midland hillocks and their valley.
Kavvayi River includes five rivers, the Kavvayi River, and its tributaries- Kankol, Vannathichal, Kuppithodu, and Kuniyan â flow together to form the Kavvayi Backwaters. The four Kanams, namely Kanayi, Vannathi, Easwaran, and Vattappoyil, in the Kavvayi River Basin were documented by researchers and have 452 plant species.