Application of water quality index (WQI) and multivariate analysis to assess the water quality of Emu stream for irrigation suitability

Surface water is essential for multiple uses and its quality directly affects the derivable ecosystem services. Consequently, physicochemical parameters like pH, dissolved solids, hardness, and nutrient levels serve as vital indicators of whether water is suitable for irrigation. Emu Stream is an important local water source relied upon for irrigation and domestic uses, yet there is scarce information on its water quality and pollution status. This study evaluated the physicochemical characteristics and irrigation suitability of Emu Stream, an important freshwater resource in Bida, Nigeria. Twenty-four water samples were collected from four stations during the wet and dry seasons and analyzed using standard methods. The measured parameters ranged as follows: pH (4.20 ± 0.63–4.89 ± 0.70), Temperature (28.70 ± 1.23–30.00 ± 1.23 °C), Electrical conductivity (15.00 ± 5.02–30.00 ± 26.29 µS cm−1), Total dissolved solids (13.32 ± 3.34–19.97 ± 17.50 mg L−1), Total hardness (43.92 ± 21.27–49.20 ± 34.09 mg L−1 CaCO3), alkalinity (27.75 ± 34.10–162.6 ± 146.09 mg L−1 CaCO3), Dissolved oxygen (5.76 ± 3.93–10.16 ± 3.52 mg L−1), Biochemical oxygen demand (1.16 ± 0.41–2.01 ± 0.48 mg L−1), Chloride (24.76 ± 15.92–94.39 ± 78.62 mg L−1), Sulphate (0.39 ± 0.05–0.48 ± 0.10 mg L−1), Nitrate (2.92 ± 1.51–5.93 ± 3.94 mg L−1), and Phosphate (1.33 ± 0.21–2.41 ± 1.05 mg L−1). Significant seasonal variations (p < 0.05) were observed in pH, temperature, and sulphate. Strong correlations were recorded between pH and BOD (r = 0.981), electrical conductivity and nitrate (r = 0.957), and hardness and sulphate (r = 0.978). Multivariate analyses identified alkalinity as a major contributor to carbonate buffering. The Water Quality Index ranged from 39.16 to 52.01, indicating good water quality for irrigation. Also, the irrigation indices, such as SAR (0.07), Na% (1.88%), KI (0.02), and PS (1.66), indicated that the Emu stream has potential for irrigation use, except for PI (16.39%). In conclusion, this study suggested that Emu Stream water is of good quality for irrigational purposes, though regular monitoring is advisable to prevent potential pollution from human activities.