15-Groundwater Development in Hilly Terrain - Case Studies in and around Kohima , Nagaland

Abstract

Significant increase in developmental activities in the State are considered as a factor responsible for scarcity of water during lean periods in most of the townships in hilly areas. With a view to ease partially the water scarcity during lean period, the State DGM has formulated strategies to harness groundwater resources in problematic rugged hilly terrains of the State which constituted almost 95% of total area. Kohima, the Capital township of Nagaland, is a fast growing urban centre broadly located on linear ridge covering an area of about 20 sq. km and has a total population of about 95,000. Highest elevation in the vicinity is 2364 m above msl and the area receives heavy rainfall during monsoon. The township is established. within semi-consolidated formations comprising shale, claystone, siltstone and fine-medium sandstone belonging to Disang and Barail Group of rocks ranging in age from Upper-Cretaceous to Recent. These geological formations had undergone various phases of deformations and tectonic processes resulting to development of secondary geo-structures, which facilitates groundwater development. Exploratory drilling of four successful shallow tube wells within 120 m depth in and around the township provided subsurface geo-hydrological data with ample scopes for judicious development of groundwater resources in hilly terrain. Static water level varies from 5 m to 39 m bgl with discharges ranging from 6000 to 9000 It/hr for a drawdown within 7 m. Construction of dug/ring wells has proved to be feasible at a specific geo-structural set-up. Generation of integrated data information system of groundwater, efficient management along with artificially recharging groundwater from rain water during monsoon period will achieve sustainable and eco-friendly development of groundwater resources in hilly state of Nagaland. Lack of geophysical inputs, high contents of iron, inaccessibility and caving at weak geologic zones are some of the constraints for development of ground water in the state.