The water quantity and quality of Laspias River, located in Xanthi Prefecture, Thrace, North Greece, are studied. A data collection program was designed at five stations along the main river course and its main tributary. Sampling frequency was about once every 10 days. Temperature (T), electrical conductivity (EC), pH, and dissolved oxygen were measured in situ simultaneously with discharge measurements. Moreover, water samples were collected and analyzed for the determination of nitrites, nitrates, ammonium, total phosphorus, biochemical oxygen demand, chemical oxygen demand, total suspended solids and alkalinity, according to standard methods. Anions (i.e., SO4-2 and Cl-) and cations (i.e., Li+, Na+, Mg+2, and Ca+2) were determined using ion chromatography (Dionex ICS-3000 ion chromatograph). The results showed that there is an impact of point (e.g., wastewater treatment plant effluent and farms) and non-point (e.g., agricultural activities) sources of pollution on the EC values, and chloride, nitrogen and phosphorus concentrations in the river water. The trophic state of Laspias River, based on nutrient concentrations, was found eutrophic. Based on the Canadian Council of Ministers of Environment Water Quality Index, the river water quality ranged from "poor" to "marginal" category, indicating the need for management measures in order to improve it.
Keywords: Eutrophication; Laspias River; irrigation water; nutrients; trophic state; water quality index.