ANALYSIS OF THE PHYSICOCHEMICAL VARIABLES OF THE STREAM WATERS OF VIZCAYA (BASQUE COUNTRY) .1. MATHEMATICAL-MODEL OF CONDUCTIVITY

A twelve-month study was carried out of 27 physico-chemical factors of the liquid medium (pH, conductivity, temperature, calcium, magnesium, etc.) and the fluviographic medium (altitude, slope, longitudinal profiles, etc.) of the river network of Vizcaya. These variables were measured at 178 sampling points distributed over 21 river courses. A multiple regression analysis, with no interaction between independent variables, was carried out on conductivity as opposed to the other physical and chemical variables, which had previously been standardized taking into account the coefficients of form of their value distribution curves, skewness and kurtosis. It was determined that five of these variables are responsible for 84.6 % of the variability, with all the statistically significant regression coefficients (p = 0.00001). These variables are temperature and the concentrations of calcium, bicarbonate, chloride and sulphate. The combination of these variables has allowed us to construct a mathematical model enabling us to predict situations of eutrophy and the degree of eutrophication of river waters, with pollution due especially to industrial emissions and the presence of saline diapirs in the outcrops of the lithosphere.