Long-Term Hydrologic Trends in the Main Greek Rivers: A Statistical Approach

Abstract

The scope of this research effort was to examine the effect of water management practices and land use changes on river flow over the last 3 decades, to identify the dominant trends in the discharge and precipitation time series and to examine the interrelationship between these two parameters. In order to accomplish these aims, the annual discharge time series of seven (7) major rivers in Greece were compared to the annual precipitation of the corresponding watersheds. This comparison was achieved through trend analysis of each time series, which involves the determination of basic statistical characteristics (normality, homogeneity, stationarity). Due to lack of satisfactory discharge time series at the downstream parts of each catchment examined, the results from E-HYPE pan-European hydrological model was used (European – HYdrological Predictions for the Environment). The main outcome of this work concludes that there is no consistent, single trend for the entire study period for any of the investigated rivers, while there are some wet and dry periods in the data which are very clear in all catchments and coincide at a temporal level. The main dry periods were at the end of the 1980s and the beginning of the 2000s. There is also a prolonged wet period during the last decade for all study catchments.