Abstract

Physico-chemical analysis of groundwater samples from Ankpa, north central Nigeria was carried out to investigate the quality of the water for drinking and irrigation purposes. The results revealed water of average low pH, indicating slightly acidic conditions of the water. The water is soft, and it is characterized as Na++K - HCO3 type. It is good for drinking and other domestic uses. Four indices were evaluated from the groundwater chemistry in order to establish the suitability of the water for irrigation purposes. They are the sodium adsorption ratio (SAR), the percentage sodium (%Na), the magnesium hardness (MH) and the permeability index (PI). The SAR values range from 0.86 to 11.19, with an average of 5.68. The interpretation indicates that the groundwater is good to excellent for irrigation. It further shows that over 90% of the samples can be classified as S1 waters, with no alkali hazard anticipated for the crops grown with the water. The range of the %Na in the groundwater in this study is between 16.28 and 73.97, with an average value of 51.27. This shows that the water ranges from excellent to doubtful for irrigation. The magnesium hardness (MH) in the groundwater ranges from 2.05 to 41.04%, with an average of 20.35%. This indicates that the entire water is safe for use for irrigation purposes. The chloride and sulphate concentrations in the groundwater indicate that the water is excellent for irrigation. However, the permeability index shows completely opposite conditions in the area, with all samples with values above 75.

Key words: Irrigation, physico-chemical analysis, water types, hydrochemical facies, Anambra Basin.