THE CHARACTERISTICS AND DISTRIBUTION OF DEEP GROUNDWATER IN DJIBOUTI

Abstract

Djibouti is one of the most arid areas in the world and rivers are not formed regularly in this region. So, groundwater has been used as the main water resource for humans and livestock. Therefore, necessary to understand the state of groundwater in terms of utilizing of sustainable water resources in this country. In this study, we measured ion contents (Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F^-, Cl^-, NO₂^-, Br^-, SO₄^2-, NO₃^-, PO₄^3-, HCO₃^- ) in groundwater using ion chromatography, and analyzed characteristics groundwater quality using by multivariate analysis based upon groundwater quality with stable isotope ratio of hydrogen and oxygen and tritium concentrations, with reference to their locations and examined the distribution analysis using GIS data of watershed maps. As a result of groundwater quality measurements, the most of groundwater samples in this study mixed with seawater or hot spring water and fossil seawater. And the concentration of NO3- in groundwater was over 50 mgL^-1 at 4 sites. In addition, as a result of the hierarchical cluster analysis, groundwater in this study showed different chemical characteristics even in the same watershed. As results of this study, although some important data of groundwater quality in Djibouti has been obtained, it is considered necessary to study in groundwater dating and water stable isotope ratios more wide area in order to understand its complex groundwater distribution and water quality characteristics.