Spatial and temporal variations of natural tritium in precipitation of southern India

Spatial and temporal variations in tritium content of precipitation at Hyderabad and Kozhikode, stations in southern India during 2005-2008 are discussed. The tritium content of precipitation varied from 1.59 to 9.21 TU for the Hyderabad station and from 0.65 to 6.11 TU for the Kozhikode station. Precipitation at the Hyderabad station had excess tritium than Kozhikode, mostly owing to its origin at higher latitudes. The predominance of marine moisture in the precipitation at Kozhikode imparts low tritium content to its precipitation during the monsoon period. The tritium concentration in precipitation of the two stations during this period is compared with that during 1997-1999. The tritium content of precipitation of both the stations showed higher values in the earlier periods, reflecting the minor contribution of residual bomb tritium that possibly prevailed during that period. The present-day tritium concentration in precipitation at the two stations suggests that the tritium level in both the stations has reached the values that prevailed during the pre-bomb era. The tritium data provided useful clues for better understanding of the mechanism of monsoonal rainfall at the two locations. Tritium inputs in precipitation and its variation in southern India, especially in the recent period are lacking. This study elucidating the present-day concentration of natural tritium in precipitation at the two stations may be helpful in applying tritium techniques for hydrological studies in the area.