Subsurface Dykes - Case Study for its Suitability in Kerala

Abstract

The average annual rainfall of 3000 mm in Kerala is 3 to 5 times more than many other states. But, in Kerala, rainwater is not much retained on the land due to the steep/undulating topography and low water holding capacity and shallow depth of topsoil. Most of the water stored in the soil during rainy season escape to the lower reaches and then to the rivers/sea. The subsurface dykes constructed at AMPRS, Odakkali using black polyethylene sheet and at Thrangalikadavu, across Bharatapuzha, using Sand-Cement-Bentonite grout was effective in increasing the sub-soil water reserve. The study revealed that water level during summer season at the dyke upstream rose by about 60 to 80cm. The wells constructed near the dyke, both for drinking water supply and lift irrigation yielded more water for longer duration.