Hydrogeochemical and isotopic characterization of the groundwater in the Dababa area (Chad)

Abstract

The Central-African country of Chad, located in the Sahel-Sahara zone, faces diverse shortages of portable water. The only reliable source of water available for drinking, domestic and agricultural use in the Dababa Division is groundwater. Conventional hydro-geochemical and isotopic methodology, coupled with piezometric data, allowed investigators to identify the numerous process affecting not only water quality, but also aided them to assess its suitability for different uses. The types of groundwater encountered indicated the presence of Ca-Mg-HCO₃, Na-HCO₃, Cl-SO₄ and Na-Ca-SO₄ in descending order of abundance. The data presented in this investigation shows three processes influenced the groundwater quality; these are the alteration of silicate minerals by dissolved CO₂, the cationic exchange and the evaporation phenomenon, in particular, in the piezometric depression. Additionally, to these findings, this article discussed the anthropogenic processes involved, whose effects are evident in many samples with nitrate concentrations above the WHO standards. Generally, the groundwater in the study area show signs of human contamination. Recent studies also indicate the development of cardiovascular diseases among the population of this area which are directly linked to the low total hardness (TH) values, or general softness, of the water. The groundwater in Dababa is, however, usable for agricultural and other domestic needs. Based on the calculation of Na‰ and the sodium adsorption ratio, the sampled waters are suitable for irrigation.

Key words: Groundwater, World Health Organization (WHO), hydrogeochemistry, isotope, Dababa, Chad.