ISOTOPIC CHARACTERIZATION OF NARMADA BASIN

Abstract

The study region comprises of the upper reaches of the Narmada Basin starting form Amarkantak (origin point) till Hoshangabad city. Two field trips were conducted in this region for sampling. The first one was at the end of the monsoon in October'2011. The second one was conducted prior to the monsoon i.e. in April'2012. Parameters such as Air Temperature, Water Temperature, R.H., Latitude, Longitude, Elevation, and Electrical Conductivity were measured during sampling. In the study area 6 major tributaries join the Narmada mainstream out of which only one joins in form the right bank. The tributaries are Burhner, Banjar, Hiran, Sher, Shakkar and Tawa of which Hiran is form the right bank. The discharge and water level data at many locations was acquired by the help of Central Water Commission, India. The samples were run in the Continuous flow Isotope Ratio Mass Spectrometer at the National Institute of Hydrology at RoQrkee for obtaining the 6180 values. Values were obtained using the Ion Vontage software. The Electrical conductivity is found to be the maximum for Groundwater samples, a little lower for tributaries and the least for the Narmada mainstream. The discharge of the Narmada mainstream is found to increase as we move downstream from Amarkantak to Hoshangabad. During April'2012 i.e. just before the beginning of monsoon, most of the tributaries had dried up and hence the discharge of the river had significantly gone down. This lead to an increase in the Electrical conductivity values as well as 6180 values for samples of the second field trip. We could also conclude that the salinity of groundwater does not depend on the season as groundwater values does not change over short durations. The evaporation in certain regions is very high and the lighter isotope evaporates enriching the water body in the heavier isotope (Fig 10).