Detection of Streamflow Trends and Variability in Karun River, Iran as Parts of Climate Change and Climate Variability

This paper describes the application of statistical and spectral procedures that identifies trends and periodicity in streamflow time series. The results of Mann-Kendall and seasonal Kendall tests (non-parametric tests which are known as appropriate tools in detecting linear trends of hydrological time series) shows negative trends especially during low water months (August to November). This downward trend is more significant in October. But these methods can not interpret periodic behavior. Hence spectral procedures were applied on data series to investigate periodicities in streamflow data series. Fourier and Continuous Wavelet Transform (CWT) analyses produce evidence of interannual variability (3–4 and 5–6 years), especially in Karun River. These oscillations can be related to ENSO phenomenon. Also we observed near decadal, PDO-related variability. However, the short length of the streamflow series can obscure such these results.