Impact Assessment of Physiography, Subsurface Hydraulic Gradients and Lithologic Heterogeneity on the Groundwater Quality

The global ongoing challenge is managing limited groundwater resources which are mainly used for irrigation and commercial uses and domestic supply. A groundwater investigation to establish baseline data for the implementation of groundwater management policy is of prime importance. The influence of natural factors, such as physiography (topography and drainage), hydraulic gradients, water table elevation and subsurface lithologic heterogeneity, is evaluated for the spatial variations of hydrochemical processes and quality for irrigation and domestic purposes. The technique utilized to establish this relationship includes the assessment of water quality, spatial analysis and multivariate statistics. Furthermore, the hydrochemical processes were unveiled using the ternary diagrams and Gibbs diagram to determine the influence of various processes. Apart from this, health risk associated with this type of groundwater and these controlling factors has also been assessed. The 94, 81, 19 and 62 percent of samples are unsuitable due to sodium adsorption ratio, residual sodium carbonate, Kelly ratio and magnesium hardness, respectively. The groundwater and the surface water constituents show characteristic hydrochemical facies, i.e., Na–HCO3 in groundwater and Ca–HCO3 in surface waters furnishing the influence of cation exchanging from north to south of the study area. In conjunction to this, the influence of precipitation, evaporation and rock water interaction is also found supporting the evidence of cation exchange process. Pearson correlation matrix revealed two significant correlations, i.e., TDS- EC, Cl−, SO2−4 and Na2+ and SO2−4 with potassium and Mg. In trace elements, Zn has a strong relation with Pb and Cu. Factor 1 includes EC, TDS, Cl−, SO2−4, Na+, Mg2+, Ca2+, K+ and Fe. Factor 2 includes HCO−3, Zn, Pb, Ni, Cd and Cu. Factor 3 includes arsenic only. A significant influence has been found by the topography, drainage, hydraulic gradients and the lithologic heterogeneity on the groundwater. Long-term usage of this water for drinking purpose pose a threat of cancer to the dwellers.