Water quality trend analysis of Cheurfas II dam, Algeria

Abstract

The northwestern part of Algeria is characterized by a semi-arid climate which has created semi-permanent rivers and dams with low filling rates. It is important to preserve the water resource, which is becoming increasingly scarce. Additionally, it is worth indicating that the mobilized surface waters are continually under threat of significant organic pollution. Indeed, the dam of Cheurfas II, in the northwestern part of the country, is indicative of this situation. In order to establish a diagnosis of the state of the temporal evolution of water quality, time series of 11 variables indicating the presence of organic pollution in this dam were thus analyzed. The data collected were analyzed using the Mann-Kendall test to look for significant trends and the Webel-Ollech test to detect the presence of seasonality. The results obtained showed increasing trends in dry residues, organic matter, phosphates and dissolved oxygen. However, variables like BOD5, COD and NO-3 showed decreasing trends. As for the variables NH+4, NO −2 and pH, they presented no trend. Finally, the water volume of the dam exhibited a significant increase. In addition, no seasonality was detected in the variables studied, with the exception of the PO43-time series and water volume. These findings indicate that the watershed of the dam received pollutants from different origins, in particular industrial pollutants. This makes water biodegradability difficult to achieve.