The objective of the study was to determine the relationship between the electrical conductivity of subsurface and surface water (ECw in dS/m at 25ºC) and the ion concentration of Na+, Ca2+ + Mg2+ and C1- (in mmol c L-1). The study was based on 75 and 100 samples collected from subsurface and surface waters, respectively, in 33 counties in the semi-arid region of the Pernambuco State. Results showed that elements Na+, Ca2+ + Mg2+ and C1- may be estimated by a single linear regression of the type, Y = a + bx, as described below: a) subsurface water; (Na+) = - 0.710 + 4.765(ECw), R² = 0.91; (Ca2+ + Mg2+) = 0.287 + 4.673 (ECw), R² = 0.83; (C1-) = - 0.569 + 6.152 (ECw), R² = 0.93 and b) surface water; (Na+) = - 0.666 + 5.072 (ECw), R² = 0.94; (Ca2+ + Mg2+) = 0.978 + 3.223 (ECw), R² = 0 78; (C1-) = - 0.874 + 6.890 (ECw), R²= 0.94.
salinity; water; irrigation; relationship
