**3. Statistics**

Basic statistics, correlation and multivariate calculations were carried out in order to give initial information about the water quality data. Calculation of means, Pearson correlations, and multiple correlations were performed using STATISTICA 7.0 software for Windows. The calculation of Pearson correlation coefficients were performed in order to evaluate the correlations between the levels of variables (water virtual pollutants within surface water, groundwater and wastewater), and multiple regression analysis was conducted in order to evaluate the interrelation between chemical pollutants from surface water, groundwater and wastewater, and predict their future evolution. All tests of significance and correlations were considered statistically significant at P values of < 0.05, < 0.01, and < 0.001 (Blenckner, 2005; Sojka et al., 2008; Kazi et al., 2009; Papaioannou et al., 2010).

During the period of five years that concerns the data collection, processing and analyze, the management of water quality in Romania was conducted and practiced, by authorities, according to requirements of the following EU directives: 60/2000/CEE, 75/440/EEC, 76/464/EEC, 91/676/EEC, 78/659/EEC, and 91/271/EEC, adopted and/or transposed in Romanian legislation (Oroian&Petrescu-Mag, 2011). They concern usual physical, chemical and ecological water indicators.

The main water pollutants identified during the period of 5 years and all water categories (surface water, groundwater and wastewater) were: nitrogen compounds, chlorine, Fe, P, Fe, Mn, Cu, Cd, Zn, pesticides, oil products and detergents.
