Résumé:
Water is a natural element essential to life and is one of the resources necessary for all human activities. It is considered the heritage of the nation. The surface waters of dams are exposed daily to variations in their quality due to several factors, mainly climatic conditions and human activities such as wastewater discharges. This study focuses on the analysis of physico-chemical and bacteriological parameters (temperature, pH, electrical conductivity, dissolved oxygen, suspended matter, chlorides, phosphates, ammonium, nitrates, nitrites, organic matter, biological oxygen demand, chemical demand in oxygen, as well as total and faecal coliforms, faecal streptococci, total germs and sulphite-reducing clostridium) from the Chorfa dam, located in the municipality of Sig, in the wilaya of Mascara. The analyzes carried out on the samples taken at the various points of the dam revealed the following characteristics of the water: a temperature between 15°C and 16.5°C, influenced by climate change; an alkaline pH ranging from 7.85 to 8.4; a dissolved oxygen concentration ranging from 5.51 to 13.2 mg/L; high electrical conductivity exceeding standards; a high concentration of chlorides; a significant presence of ammonium; nitrate, nitrite and nitrogen levels above WHO standards; a very high suspended matter content; phosphate concentrations above the norm; levels of organic matter in the waters of the dam exceeding the standards; a biochemical oxygen demand (BOD5) and a chemical oxygen demand (COD) exceeding the Algerian standard; the presence of taste, odor and color in the dam water constitutes proof of pollution. The results obtained indicate that the physico-chemical and organic quality of the raw water from the dam is poor, since almost all the samples do not comply with Algerian standards. Consequently, we recommend establishing a diagnosis of the state of the quality of the surface waters of these dams.
