An integrated indexical approach in assessing physico-chemical water quality for drinking purposes in the Nkalagu area, southeastern Nigeria

In this study, water supplies for the two distinct climatic seasons, wet and dry seasons, were evaluated. This was carried out to determine the degree of contamination and whether the water supplies were safe for human consumption. In light of this, four water quality indices; the vector modulus of Pollution Index (PI_vector), Entropy-weighted Water Quality Index (EWQI), Integrated Water Quality Index (IWQI), and Modified Water Quality Index (MWQI) were integrated. Based on the results, the pH of the analyzed water samples varied from 6.02 to 7.92 with a mean value of 7.2 during the wet season and from 5.25 to 8.25 with a mean value of 6.82 during the dry season. A generic quality assessment study revealed that Pb, As, during the wet season and Pb, As, and Mn during the dry season has the greatest effects on the region's water supplies. According to the indices, PI_vector classified approximately 71.43% of the water during the wet season as unpolluted and 28.57% as polluted, and 37.14% of the water during the dry season as unpolluted and 62.86% as polluted. Similarly, the EWQI classified 65.71% as safe water and 34.28% as unfit for human consumption during the wet season, whereas, 34.28% and 65.72% as safe and unfit, respectively for the dry season. According to IWQI, during the wet season, 25.7% of the water is considered acceptable for drinking, while 74.3% is unsafe, and during the dry season, 14.85% is acceptable and 85.15% is unsafe. The MWQI results indicated that the water samples for the wet season were classed as "fair" water suggesting they are occasionally threatened while, for the dry season as “marginal” water indicating they are frequently threatened. Summarily, the results show that the water resources are safer and less contaminated in the wet season than in the dry season, which is attributed to the impact of rainfall, which reduces the mobility of contaminants, as well as the influence of vegetation cover.