A study on the spatial variations in stable isotopic composition of precipitation in a semiarid region of Southern India

Abstract

The stable isotope analysis of all major rain events from Moinabad (MB), Rajendranagar (RN) and Osmanasagar (OS) reservoir, three closely placed locations in Hyderabad, India, were carried out during the 2005 to 2008 period. The OS station recorded the highest amount of rainfall with an average value of 1000 mm, whereas the MB station recorded the lowest average rainfall of 790 mm. The stable isotope (d 18 O) values of the precipitation samples during these period varied from À11.43% to À0.03% for the MB station, À8.21% to 0.54% for the RN station and À11.47% to 0.72% for the OS station. The d-excess of precipitation at the three stations also showed considerable variations and revealed that the precipitation in the region undergoes significant modification through secondary evaporation during its fall. The possible causes for these observed spatial and temporal variations in amount and the isotopic composition of precipitation in a small geographical area within the city were studied. The observed variations may be attributed to the regional scale differences in water budget induced by rapid urbanisation activities in the city coupled with the differences in secondary effects undergone by the falling drops. This study elucidating changes in precipitation patterns in the city and its possible causes may largely help in its water balance calculation.

The Significance of Hydrogen and Oxygen Stable Isotopes in the Water Vapor Source in Dingxi Area

“…The stable isotope technique has been widely applied in many research areas, especially in hydrology, giving solutions for discovering the origin and formation of different water bodies [1][2][3][4]. As a tracer of water sources and hydrological processes [5], hydrogen and oxygen isotopes have contributed significantly to reflecting the atmospheric, land surface, and groundwater characteristics [6] and to our understanding of the evolution process of the water cycle in different geographical regions [7][8][9][10]. Due to the isotopic fractionation, there is a linear correlation between δ 18 O and δD, defined as the global atmospheric water line by Craig [11].…”