The State and Origin of River Water Composition in Greece

Abstract

This chapter provides an overview on the hydrogeochemical and pollution characteristics of Greek rivers and attempts to interpret the origin and spatio-temporal variability of their composition as it emerges from various natural factors and processes and human interference. Despite the highly variable physicogeographic and geological conditions of the country, river basins may be hydrogeochemically classified into three main geographical zones with distinct geological, climatic and hydrological features. River hydrogeochemical properties mainly depend on geochemical, hydromorphological and climatic factors. Catchment geology directly controls solute concentrations and major ion portions and influences hydrological and hydrogeological factors. The latter indirectly control water temperature and solute concentrations, as well as pH and carbonate equilibrium together with biological activity. In certain river basins, anthropogenic pressures (i.e. inadequately treated municipal wastes, agrochemicals, agro-industrial and mining effluents) affect aquatic quality, whereas water resources management (i.e. water overexploitation for irrigation and dam operation) alters the hydrological regime, thus indirectly influencing solute concentration. In general, rivers located in western Greece as well as mountainous rivers and streams range from “pristine” to satisfactory conditions. On the contrary, lowland sections of large rivers are at a greater risk due to a variety of pressures, such as agriculture, agro-industry, mining, (illegal) building, and tourism. Despite the great number of internationally important sites in river basins and, the recent, major efforts made in implementing the WFD, Greek rivers are still threatened from insufficient implementation of environmental legislation and ad-hoc management practices. The economic crisis may set environmental conservation at the expense of economic development and/or change socio-economical attitudes. thus pushing environmental conservation forward.