Tectonic Consideration for Location of the Kishau Dam Site on Tons River in lesser himalaya, india

Abstract

A 236 m high concrete gravity dam named Kishau dam is proposed on Tons river in Lesser Himalayan region of Uttarakhand state of India. The possible site for this upcoming dam on Tons river lies in the close proximity of Tons thrust which makes a tectonic boundary between allochthonous rocks of Krol nappe and the autochthonous Simla Group rocks. The Tons thrust lies in the close vicinity of the proposed dam site. Many geomorphic and geological evidences have been observed around the dam site which indicate that active tectonics is prevalent in the region. The present study examines the geological structures of the region in order to understand the tectonic conditions that the area has experienced and finds that the southward movement of the Krol nappe is responsible for active tectonics in the region. Due to mass transfer by the movement of Krol nappe from over the autochthonous zone, the autochthonous zone is getting uplifted at an average rate of 9.7 mm/per year. In light of these active movements, the Kishau village, which lies in the southwards moving allochthonous zone, cannot be good site of Kishau dam and the dam location should preferably be placed across the Tons thrust in the autochthonous zone.