Hydrogeochemical analysis and quality evaluation of groundwater from Onicha-Uburu, Southeastern Nigeria for irrigation purposes

Abstract

A total of 20 groundwater samples from boreholes and hand dug wells withinOnicha-Uburu and its environs were assessed to determine their suitability for irrigation purposes. Physical and hydrogeochemical parameters were evaluated, while techniques such as sodium absorption ratio (SAR), sodium percent, residual sodium carbonate (RSC) and magnesium adsorption ratio (MAR) were used to assess the suitability of these groundwater samples for the intended purpose. Results indicated that temperature ranges between 20 and 26°C for hand dug wells and 19 and 23°C for borehole samples. The electrical conductivity (EC) varies from 8.4 to 36.4 μs/cm for the hand dug wells and 10.0 to 76.4 μs/cm for the borehole water samples, while pH values range between 7.0 and 9.0 for the entire samples and indicate alkaline water. Statistical analysis shows appreciable concentrations of basic ions (average value of 28.8 mg/l for Na⁺, 9.1 mg/l for K⁺, 16.0 mg/l for Ca²⁺, 14.6 mg/l for Mg²⁺, Nil for C0₃^2-, as well as 45.0 mg/l for HC0₃ -, 20.5 for mg/l Cl^- and 8.7 mg/l for S0₄ ^2-). While Na⁺ and Ca²⁺ are the predominant cations, HC0₃^- and Cl^-1 are the anions that predominate. The chemical analysis revealed that the total hardness (measured in terms of CaCO₃) varied from 16 to 140 mg/l for both sets of samples indicating soft to moderately hard water. Based on the values of EC, percent sodium, SAR (which vary from 0.3 to 1.7 meq/l), RSC (from 0.1 to 0.99 meq/l less than the standard value of 1.25 meq/l) and the magnesium hazard (MH) values which range between 0.99 and 89.8%, revealed that water samples from the study area are generally suitable for irrigation purposes except for few locations.

Key words: Groundwater, hydrochemical facies, hydro-geochemical analysis, irrigation purposes, Onicha- Uburu area.