Abstract

In the present study, the isotopic signature of atmospheric vapor/precipitation is used to identify the source of air moisture at Roorkee, Uttarakhand, India. The interpretation of the isotope data of atmospheric vapor for the years 2008-09 indicates that the seasonality effect divides the entire data spectrum into three sub-units as: monsoon water vapor (δ18O<-25, δD<-126) of Bay of Bengal (BoB)/oceanic origin are the most depleted; the most enriched vapors (δ18O>-5, δD>-6) of local origin and the vapors originating due to Western Disturbances (WD) have values (δ18O ~-15, δD~-53) between these two sources. The monsoon showers are isotopically the most depleted with the highest slope (7.78) of its characteristic line followed by winter rains which are marginally enriched. The pre-monsoon showers are the most enriched rains in the year. With these systematic it can be easily differentiated between premonsoon and monsoon rains and in identifying the true monsoon rains or onset of monsoon.

Keywords: Hydrology; Water cycle; Atmospheric vapour; Stable isotopes; Arabian Sea; Bay of Bengal; Mediterranean Sea