Assessment of Monthly and Annual Discharge Trends of the Darreh Dozdan River Using Nonparametric Tests

The most common method for hydrological time series analysis is to investigate the presence or absence of trends in them using statistical tests. Investigating quantitative changes in river water and their impact from human activities and climate change is one of the goals of assessing the time trend of river discharge. The aim of this study is to evaluate the time series trend of Darreh Dozdan River discharge on a monthly and annual scale. In this study, monthly discharge data from the Tange Siab station for the years ۱۹۷۰ to ۲۰۲۲ were used. The Mann-Kendall test was used to assess trends in the time series of monthly and annual discharge, and the Sen's slope estimator was used to calculate the slope of the trend line. The results of the Mann-Kendall test and Sen's slope estimator show that the annual discharge of the Darreh Dozdan River has had a significant decreasing trend (Z = -۵.۱۱, Qmed = -۰.۰۱۶) over the ۵۳-year period. This trend is statistically significant at both the ۵% and ۱% levels. The results of the Mann-Kendall test and Sen's slope estimator show that all months from January to December, except February, show significant decreases in discharge at the ۵% level. The decrease in February discharge (Z = -۱.۸۲) is not statistically significant, suggesting that while there may be a downward trend, it is not as pronounced as in other months. These results can help policymaking and sustainable management of water resources in the basin of this river.

کلیدواژه ها:

Discharge ، Time Series Trend ، Mann-Kendall ، Sen's Slope Estimator