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effluents. An increasing concentration is observed for most of these substances. The increase and the decrease of 4.3% in pH, suggests a degradation of by microorganisms. This degradation was accompanied by a decrease of 2% of 100%, are related to a n of NO 3 where latters declined by 77%. These increases are related also to the large amount of human and animal fertilizers. Research ArticleA.Mebarkia et al.

Water resources scarcity in Algeria, their fragility and their unequal distribution have resulted in a serious shortage, which, in spite of all the efforts, seems inevitable. This study consists of evaluating the impact of human activity on the water quality of Aïnzeda lake (NE Algeria), a typical case study of the difficulties posed by the problem of surface water quality in semi-arid regions. Principal Component Analysis (PCA) and the trend method were applied to interpret the physico-chemical data of monthly analyzed samples, over a 25-year period (1988–2012). The trend method results show that most chemical elements have a direct relationship with urbanization and agricultural practices in the area. The change in the watershed climatic conditions (increase of 9% in air temperature, 7% in the lake water temperature, and decrease of 8% in precipitation) is also responsible for the degradation of the water quality. The PCA shows that salinization (51.73%), and anthropogenic and agricultural pollution (13.49%) are the most significant degradation factors. These two approaches have enabled us to prove that aridity and anthropogenic or agricultural activities have a negative impact on the lake's surface water quality.