Groundwater Quality Index Assessment using the Entropy Method on the Nineveh Plain in Northern Iraq

Human health is greatly and directly affected by the quality of groundwater and the extent of its pollution. This research evaluated the quality of groundwater in the Nineveh plain in northern Iraq and determined the suitability of groundwater for drinking purposes. Sixty-nine groundwater samples were taken and the major physical and chemical constituents, including pH, TDS, EC, Ca2+, Mg2+, Na+, K+, Cl−, So42-, HCO3-, and NO3-. were analyzed to use in calculating groundwater quality index for drinking purpose based on the World Health Organization standards for the year 2017. To prevent subjectively assigning weights in the calculation groundwater quality index, the entropy information theory was used. The estimated groundwater quality index values were loaded into ArcGIS 10.8 as a point, shapefile and interpolated using Empirical Bayesian Kriging techniques to produce the final groundwater quality index map of the study area. Results indicated that the entropy groundwater quality index for 2.9% of the samples were within the excellent range, 33% were in the good range, 14.5% were within the moderate range. The groundwater quality index values range between (48-581.8). These values were manually classified into five categories: >200 (very poor), 200-150 (poor), 150-100 (moderate), 100-50 (good), and <50 (excellent). The study discovered that the excellent class occupies 0.2 % (50.9 km2) of the study area, while the good class occupies 23.4% (596 km2), the medium class occupies 18.6 % (473.7 km2), and the poor and extremely poor classes occupy 26.1 % (664.8 km2) and 31.7% (807 km2), respectively.