Residual sodium carbonate (RSC)
Carbonate and bicarbonate are an important parameter for assessing the
suitability of groundwater for irrigation uses. The RSC value indicates
the alkalinity hazards of earth metals. An excessive concentration of
the sum of carbonate and bicarbonate in groundwater over the sum of
calcium and magnesium also influence the fitness of groundwater
(Balamurugan et al., 2020a). In the study region, the RSC value ranges
from -23.96 to 3.01, with a mean of -6.31 (Table.4). The negative value
of RSC reveals that concentration calcium and magnesium are higher than
those of carbonate and bicarbonate in groundwater. The value of RSC less
than 1.25 meq/L is suitable, 1.26 to 2.5 meq/L is marginal, and greater
than 2.5 meq/L is unsuitable for irrigation (Table.6). The spatial
distribution of RSC value in the study region, 664.91 sq.km areas, is
suitable, 1.94 sq.km areas is marginal, and 0.57 sq.km area falls under
the unsuitable classes of groundwater (Fig.11c). It indicates that one
sample location has a distribution of calcite- and dolomite-rich
sediments and large amounts of bicarbonate.