The isotopic compositions of oxygen (δ 18O) and hydrogen (δ 2H) of precipitation were determined from three different locations in the western Niger Delta (Warri, Ughelli and Abraka) between 2014 and 2015. 18O and 2H in wet season precipitation were more depleted compared to the dry season. Similarly, d-excess computed for wet season precipitation is lower than that for the dry season. The δ 18O and δ 2H variations in precipitation suggest the effect of the convective system and north-easterly and south-westerly trade winds. The decrease in δ 18O and δ 2H was also observed in precipitation data of a continuous rain event of two successive days. The local meteoric water lines estimated for Warri, Ughelli and Abraka were δ 2H = 8.8 δ 18O + 9.1 ‰ (R 2 = 0.93), δ 2H = 6.9 δ 18O + 10.7 ‰ (R 2 = 0.98) and δ 2H = 7.9 δ 18O + 11.3 ‰ (R 2 = 0.87), respectively. The Niger Delta regional meteoric water line of δ 2H = 7.7 δ 18O + 10.2 ‰ (R 2 = 0.91) was derived from the monthly average from the three locations. The provided local meteoric water line for the Niger Delta from unweighted stable isotopic data represents a baseline for regional water resources studies.
Keywords: Deuterium excess; Niger Delta region; Nigeria; hydrogen-2; isotope hydrology; meteoric water lines; oxygen-18; precipitation; trade winds.