Values of δD and δ18O and concentrations of 3H and 14C of deep groundwater in Djibouti

• Published in: Journal of Arid Land Studies Vol. 32; no. S; pp. 71 - 75
• Main Authors: ASAKURA, Yasuhiro, OFLEH, Bouh Houssein, NAKANISHI, Yasuhiro
• Format: Journal Article
• Language: English
• Published: The Japanese Association for Arid Land Studies 30.12.2022
• Subjects: arid; carbon-14; groundwater dating; stable isotopes; tritium
• ISSN: 0917-6985; 2189-1761
• DOI: 10.14976/jals.32.S_71

In Djibouti, as the amount of the fresh water is not large enough, deeper groundwater recharged in the volcanic aquifer has been developed and it is considered to be a new source of fresh water in most of the region of the country. Although some studies have been conducted to find out the volume, depth, quality and age of groundwater, the data is not still enough to construct a scheme of agricultural development using the deeper groundwater in large area of Djibouti. Therefore, the first purpose of this study is to estimate the original recharged area of the deeper groundwater of this country, using stable isotope (δD and δ18O) analysis, and secondary to calculate the age of groundwater, using radioactive isotope (3H and 14C) analysis. We have collected groundwater samples from 16 wells in 4 districts (Djibouti City, Arta, Ali-Sabieh, and Dikihil) in 2019. The results on δD and δ18O showed a possibility that the recharge areas were not simple in the complicated geological condition with lots of various faults even the location of wells is close. The concentration of 3H on the 6 samples was very low (under 0.3 T. U.), indicating that the age of the groundwater samples was older than 70 years.