Natural regime of streamflow trends in Macedonia

Abstract

This study investigates the annual and seasonal trends of minimum, mean and maximum streamflow, analyzed on 13 gauges/streams with natural regime, predominantly mountainous and homogeneously distributed in the studied area. The varying period of at least 40 years is used in the analysis. After the pre-whitening TFPW method was applied, the Mann-Kendall and Sen’s slope tests were used for trend testing. The analysis detects significant decreasing trends in the country (according to a = 0.1 significance level). In general, the streamflow shows levels of decrease in almost all streams with lower or higher magnitude (from 0.1 to 0.01). The results provide a unique assessment of streamflow trends in the country and the current findings are consistent with those in other regions of Europe, especially in Southern Europe. Significant trends of decrease have been found in each of the 13 streamflow gauges throughout Macedonia without a single positive significant trend. The test confirmed the general decreasing streamflow trend in the country; even the stations without any significant decreasing results are generally heading downward.