Impacts of natural conditions and anthropogenic activities on groundwater quality in Tebessa plain, Algeria

摘要

The “Merdja” is the shallow aquifer of Tebessa plain, located in the northeast of Algeria. The climate is typical of semi-arid steppes, where extensive agro-pastoral activities are dominating. It is still the main water resource used by major sectors. Due to its proximity to the City, it is vulnerable to pollution. According to earlier studies, this aquifer undergoes seasonal water quality fluctuations (between wet and dry seasons), induced mainly through anthropogenic activities. The study is utmost important, as it tracks the groundwater quality and aims to gain an understanding of how the local and natural conditions influence this resource at temporal (interannual) and spatial scales, by following up the evolution trend of hydrochemical parameters of the “Merdja” aquifer. Seventy-one groundwater samples were collected and analyzed from drinking/irrigation wells, through four field measurement campaigns (2001, 2006, 2009, and 2010). The results obtained confirm the fact of water pollution. Point-sources of pollution with nitrate and salinity are revealed on the respective maps of these parameters, especially downstream at the nearby areas of Tebessa City. Non-point sources of groundwater pollution are also manifested. The Piper diagram reveals a relative stability of water type and that rainfall plays a role in the natural remediation, by taking part in the aquifer recharge. The ionic ratios and the principal components analysis highlight that the temporal change of groundwater quality results respectively from: (i) ionic exchange process and the dissolution of evaporites; (ii) the sources of nitrate in groundwater remain the excess application of inorganic nitrogenous fertilizers, organic manures, and wastewater effluents.