Trends of precipitation and stream-flow in Gediz river basin, Western Turkey

In this study, it was attempted to interpret the trends in annual precipitation totals and annual mean stream-flow records in Gediz basin located in Western Turkey. The data used consisted of 1966-1998 records of 14 precipitation and 4 stream-flow gauging stations. The trend analysis was performed by applying sequential versions of non-parametric statistical Mann-Kendall and Pettitt tests. The results showed a decreasing tendency for annual precipitation with change points in the beginning of the 1980s and similar downward trends for stream-flow records with change points concentrated around the mid-1980s. This trend of stream-flow pattern in the basin could be directly explained by precipitation decrease during the same period. All the trends of hydro-climatic variables were entirely consistent with those identified in recent studies carried out in Turkey and several southern Mediterranean countries.