Characteristics of water resources in Dalmatia according to established standards for drinking water

The purpose of this study was to monitor and record the specific characteristics and properties of most of the important water resources in Dalmatia (southern Croatia) for a period of 5 years (1994–1998). A detailed account of their chemical content classification and concentration of salts is presented. Bacteriological pollution levels are indicated by the total coliform bacterial levels (MPN coli/100 ml).

The water characteristics are expressed by coefficients which represent the ratios between water components. The Ca/Mg eq ratio, SO₄/Cl eq ratio and K₁ and K₂ for bicarbonate hardness were calculated. The concentration of anions shows a stability from which it is possible to predict probable content and availability of salts in these waters. The hygienic characteristics of the water samples were expressed by the total coliform bacteria estimation (MPN coli/100 ml), the permanganate consumption (KMnO₄) and biological oxygen demand (BOD₅).

Typical karst waters in Dalmatia are moderately hard, the SO₄/Cl ratio is 0.38–1.6, they are non-corrosive (K₁ lower than 0.2), and not significantly mineralized (<500 mg/l minerals). Sulphate waters are generally hard, the SO₄/Cl ratio is higher than 1.6, and K₁ is 0.2–0.65. Marine waters are quite hard or hard, particularly at the river estuaries, the SO₄/Cl ratio is lower than 0.38, and K₁ is higher than 0.65.

The groundwater and springs in Dalmatia are less polluted than surface waters. A majority of these have a geometric average value of MPN coli <150/100 ml of water, observed in 24 out of 42 locations studied. The highest bacteriological pollution was found in nine locations where MPN coli >1,000/100 ml, and moderate pollution was found in nine locations where MPN coli was between 150–1,000/100 ml of water.

The overall changes in water quality can be correlated with the epidemiological prevalence of water-borne diseases, particularly bacterial diarrhoeas, and can reflect the demographic distribution of water-borne diseases, i.e. overall health status.