Physiography

Kerala, located on the windward side of the Western Ghats, receives an average annual rainfall of about 3000 mm, with higher altitudes like Wayanad and Idukki witnessing up to 5000 mm during monsoons. The state experiences varied temperatures: 23°C at elevations below 700 m, 16–23°C at 700–1400 m, and around 13.5–16°C above 1400 m, where unique shola forests thrive.

Kerala has 44 perennial rivers, with three flowing eastward and 41 draining into the Lakshadweep Sea. These rivers, characterized by steep gradients and swift flow, lack delta formation and primarily follow a dendritic drainage pattern, though trellis, sub-parallel, and radial patterns also occur. The four medium rivers, namely Chaliyar, Bharathapuzha, Periyar and Pamba have a total drainage area of only 8250 km2 with length 169 km, 209 km, 244 km and 176 km respectively. The length of rest of the rivers varies from 16 km to 130 km, with an average length of 62 km and total drainage area of 19,485 km2 . The river flow is modulated by about 30 reservoirs, mostly located in highlands. Kerala also features two freshwater lakes, Pookot and Sasthamkottah, along with 46.13 km² of estuaries and backwaters, notably the Vembanad and Ashtamudi lakes.

Ten major soil types, including laterite, coastal alluvial, and forest soils, support diverse ecosystems. Forests, comprising dry deciduous, moist deciduous, semi-evergreen, evergreen, and shola types are seen on the one hand while agriculture and settlements occupy the rest. Forest conservation is concentrated in higher altitudes.

Kerala’s terrain is divided into three natural regions: highlands, midlands, and lowlands. The three major regions of Kerala include :