Stable isotope characteristics of precipitation of Pamba River basin, Kerala, India

Journal of Earth system science

K V Sudharma1¹  A Shahul Hameed1¹  T R Resmi1¹ 

[1] Isotope Hydrology Division, Centre for Water Resources Development and Management, Kunnamangalam P O, Kozhikode, Kerala 673 571, India.$$

关键词: Isotope ratio;    precipitation;    spatiotemporal variation;    statistics;    tropical river basin;   

DOI  :  

学科分类：天文学(综合)

来源: Indian Academy of Sciences

【 摘 要 】

Stable isotope composition of precipitation from Pamba River basin, Kerala, India, is evaluated to understand the role of spatial and temporal variations on rainwater isotope characteristics. Physiographically different locations in the basin showed strong spatial and temporal variations. δ18O varied from −7.63 to −1.75‰ in the lowlands; from −9.32 to −1.94‰ in the midlands and from −11.6 to −4.00‰ in thehighlands. Local meteoric water lines (LMWL) for the three regions were determined separately and an overall LMWL for the whole of the basin was found to be $delta^2$H = 6.6 (±0.4) $delta^{18}$O+10.4 (±2.0). Altitude effect was evident for the basin (0.1‰ for $delta^{18}$O and 0.8‰ for $delta^2$δ2H per 100 m elevation), while the amount effect was weak. The precipitation formed from the marine moisture supplied at a steady rate, without much isotopic evolution in this period may have masked the possible depletion of heavier isotopes with increasing rainfall. Consistently high d-excess values showed the influence of recycled vapour, despite the prevailing high relative humidity. The oceanic and continental vapour source origins for the south-west and north-east monsoons were clearly noted in the precipitation in the basin. Rayleigh distillation model showed about 30% rainout of the monsoon vapour mass in the basin.

【 授权许可】

Unknown